Are predatory mites effective as biological control agents to suppress Oligonychus ilicis (Acari: Tetranychidae) in blueberry plantings?

Southern red mite, Oligonychus ilicis McGregor (Acari: Tetranychidae), is an important polyphagous spider mite pest that causes economic damage to many ornamentals, coffee, and fruit crops. Blueberry growers in the Southeastern United States, including Florida and Georgia, have experienced severe losses due to outbreaks of O. ilicis. Predatory mites are an important management tool used for controlling spider mites; however, predators have not been studied and successfully evaluated in blueberry systems. Amblyseius swirskii Athias-Henriot, Phytoseiulus persimilis Athias-Henriot, and Neoseiulus californicus (McGregor) (Acari: Phytoseiidae) are among the most economically important arthropod agents used in augmentative biological control worldwide. To evaluate the potential of these 3 commercially available predatory mites for use in blueberry plantings, we conducted experiments under controlled laboratory conditions and in the greenhouse. In preliminary laboratory experiments, P. persimilis and N. californicus significantly reduced the number of O. ilicis motile stages below those found in the untreated control, indicating the potential for these 2 predatory mite species to suppress O. ilicis populations. Amblyseius swirskii did not perform well controlling O. ilicis motiles in the laboratory. Under greenhouse conditions, N. californicus and P. persimilis significantly reduced the number of eggs after 7 days of release and the number of motile stages after 14 days of release. This is the first report of using phytoseiid mites to suppress O. ilicis in blueberry systems in the United States. Further studies on predator behavior, feeding preferences, and acaricide compatibility with predators are required to investigate the possibility of using P. persimilis, and N. californicus as biological control agents of O. ilicis in blueberry systems.

Delayed spinetoram application is useful in managing Scirtothrips dorsalis Hood (Thysanoptera: Thripidae) in Florida strawberry

Scirtothrips dorsalis Hood (Thysanoptera: Thripidae) is an invasive, early-season pest of strawberry in Florida, causing feeding injury to young foliage that results in stunted plant growth and yield loss. Spinetoram, an effective insecticide for thrips pests with up to 3 applications per season permitted in strawberry, is often applied repeatedly during the early-season (Oct-Nov) to manage S. dorsalis, leaving few or no applications for flower thrips pests later in the season (Dec-Mar). Therefore, new strategies are needed to manage S. dorsalis with less insecticide, with the hypothesis that the first insecticide application can be delayed because young strawberry plants can compensate for minor feeding injury without compromising strawberry yield. Experiments conducted in strawberry field plots in Balm, FL, during 2018 and 2019 showed that delaying a spinetoram application for 14 days after infesting a plant with zero, 5, 10, or 20 S. dorsalis adults did not reduce the plant vigor and yield compared to spinetoram application after 4 days. Furthermore, young plants recovered from injury (10-30% bronzing injury on leaf veins and petioles) due to 1 or 2 S. dorsalis adults or larvae per trifoliate. A strategy of delaying the first spinetoram application when plants have 4-5 trifoliates should help reduce the number of insecticide applications needed for S. dorsalis management and reserve spinetoram applications for later in the season. Lower input costs in Florida strawberry without compromising yields due to thrips damage will improve the economics and sustainability of production systems.

Comparison of multimodal attract-and-kill formulations for managing Drosophila suzukii: Behavioral and lethal effects

Attract-and-kill (A&K) is a potential alternative control tactic for managing the invasive spotted-wing drosophila, Drosophila suzukii Matsumura. Here, we compared the efficacy of two novel A&K formulations based on proprietary blends-ACTTRA SWD OR1 (henceforth OR1) and ACTTRA SWD TD (henceforth TD)-in managing D. suzukii. Using two-choice bioassays, we compared OR1 and TD for their relative attractiveness to adult D. suzukii. Additionally, we tested how the addition of (1) a red dye (visual cue) and (2) the insecticide spinosad (Entrust™) to the OR1 and TD formulations influenced the attraction of adult D. suzukii in the presence of blueberry fruits. Finally, complementary laboratory efficacy (no-choice) bioassays were conducted to assess the mortality of adult D. suzukii exposed to OR1 and TD. A direct comparison between TD and OR1 formulations indicated the TD formulation was ~8 times more attractive than OR1. Adding a red dye to the TD or OR1 formulation did not significantly alter the attraction or mortality of adult D. suzukii compared to the formulation without a dye. Similarly, irrespective of dye status, adding spinosad to either the TD or OR1 formulation did not alter the adult D. suzukii behavioral response to these formulations but resulted in significantly higher D. suzukii mortality. Overall, the TD formulations resulted in significantly higher, or at least comparable, mortality to the OR1 formulations. In summary, our laboratory results demonstrated the higher efficacy of a TD-based A&K product in managing D. suzukii over its well-tested predecessor, the OR1 formulation, confirming its potential as a new behavioral tactic against this pest.

Integrated Effect of Plastic Mulches and Biorational Insecticides in Managing Tomato Chlorotic Spot Virus (TCSV) and Its Vector Thrips in Tomatoes

In the USA, tomato chlorotic spot virus (TCSV) was first identified in Miami-Dade County of Florida in 2012. This viral disease is transmitted by thrips (Thysanoptera: Thripidae) of different species, imposing a serious threat to the entire tomato production in the state. Both cultural and chemical control techniques could be essential tools to combat this vector-borne disease. In the present two-year-long study, we determined the effect of different types of plastic mulches and biorational insecticides on managing thrips and TCSV. Results from the leaf and flower samples showed a significantly lower adult thrips population in Entrust®SC treated tomatoes than in other treated and untreated tomatoes in 2018. Silver on black and silver on white reflective plastic mulches significantly reduced the adult thrips population in 2018. In both study years, marketable yield was significantly higher in tomatoes treated with Entrust®SC and reflective plastic mulches than in other treatments. The incidence of TCSV was significantly reduced in tomatoes treated with Entrust®SC and reflective plastic mulches than the untreated control in 2018. Marketable yield was negatively correlated with the thrips population, as observed from the Pearson correlation coefficient analysis. This research describes a potentially viable management program for thrips and thrips-transmitted TCSV.

Miticidal Tools for Management of Southern Red Mites Infesting Southern Highbush Blueberries

Tetranychid outbreaks have been detected since 2016 in southern highbush blueberries (SHB); however, it was not until 2019 that the southern red mite (SRM), Oligonychus ilicis (Acari: Tetranychidae) was confirmed as the pest causing severe bronzing and stunting, in multiple Florida and Georgia commercial blueberry plantings. To date, only three miticides (fenazaquin, fenpyroximate, and acequinocyl) have been registered for use in SHB and there are no clear guidelines on how to manage SRM in SHB. Similarly, there is no knowledge regarding the existence of natural enemies of SRM in SHB. This is the first report of naturally occurring predatory mites (Amblyseius sp. and Neoseiulus ilicis) associated with SRM in SHB. Predatory mites were recorded in blueberry bushes after treatment with seven miticides used to suppress SRM populations including spiromesifen, acequinocyl, sulfur, sulfur + molasses, bifenazate, fenpyroximate, and fenazaquin. The number of SRM recorded per leaf and averaged plant damage ratings (0 = no bronzing-4 = 100% bronzing) were used to evaluate miticide efficacy. Additionally, the presence or absence of predatory mites per sample was recorded. Fenpyroximate used as the standard miticide, significantly reduced mite numbers seven days after application, as well as acequinocyl and fenazaquin. Fenpyroximate and fenazaquin demonstrated the best performance for managing O. ilicis on SHB and treated bushes demonstrated significantly less bronzing compared with the control plants. These miticides were also safe to naturally occurring predatory mites. Lastly, the level of growers' awareness regarding SRM was assessed using surveys in 2020 to design adequate educational materials available to the grower community.

Potential Alternatives to Spinosad as the Killing Agent Mixed With Two Attractant Products in Attract-and-Kill Formulations Used to Manage the Spotted-Wing Drosophila, Drosophila suzukii (Diptera: Drosophilidae)

Spotted-wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), is a key pest of many berry and fruit crops worldwide. The primary method of controlling this pest is the application of insecticides. Attract-and-kill is a management tactic that may reduce the number of insecticide applications needed to manage D. suzukii. ACTTRA SWD OR1 and ACTTRA SWD TD, developed by ISCA Technologies Inc., combine D. suzukii attractants with a gel matrix. Growers add an insecticide as a killing agent. The only USDA National Organic Program approved organic insecticide that has been shown to be effective as a killing agent is spinosad. This study aimed to determine the efficacy of other USDA National Organic Program approved organic insecticides, including Grandevo 30 WDG (Chromobacterium subtsugae strain PRAA4-1 30%), MBI-203 SC2 (C. subtsugae strain PRAA4-1 98%), Venerate XC (Burkholderia spp. Strain A396 94.45%), MBI-306 SC1 (B. rinojensis Strain A396 94.45%), Azera (azadirachtin 1.2% + pyrethrins 1.4%), and PyGanic (pyrethrins 1.4%), when used as the killing agent with the two ACTTRA SWD products. Lab and cage bioassays were conducted. Entrust (spinosad 22.5%) and PyGanic were the only compounds that showed some efficacy when used with ACTTRA SWD OR1 and ACTTRA SWD TD.

Within-Plant and Within-Field Distribution Patterns of Asian Bean Thrips and Melon Thrips in Snap Bean

Asian bean thrips, Megalurothrips usitatus Bagnall, are a serious pest of vegetable crops, especially leguminous crops, across the Asian continent. In Florida, it is a new invasive pest of snap beans. In 2019, it was recorded for the first time in the United States in snap bean (Phaseolus vulgaris) fields. Another thrips species, melon thrips, Thrips palmi Karny, is also a serious pest that affects several vegetable crops. Within-plant and within-field distribution patterns of M. usitatus and T. palmi were determined in snap bean fields in southern Florida. The highest number of both thrips species (Asian bean thrips and melon thrips) in snap beans were in flowers, followed by leaves and pods. Both adults and immatures of these thrips exhibited regular to clumped distribution patterns in bean fields. Several statistical indices showed agreement in the distribution patterns of Asian bean thrips, melon thrips, and larvae, irrespective of sampling units and plot size, in three years of study. In most instances, the distribution of Asian bean thrips and melon thrips was aggregated. This study assessed the optimum sample size to accurately determine the population density of these thrips for management purposes. The results from this study will be useful for implementing targeted management programs against thrips pests, thereby reducing labor costs and time. This information will also help reduce agrochemical use.

Using Red Panel Traps to Detect Spotted-Wing Drosophila and its Infestation in US Berry and Cherry Crops

Spotted-wing drosophila (SWD), Drosophila suzukii Matsumura (Diptera: Drosophilidae), is an invasive pest of thin-skinned fruits in the United States. Monitoring traps are an integral part of SWD integrated pest management, allowing early detection and timely management of this pest. An ideal monitoring trap should be easy to use, effective in capturing SWD, sensitive and selective to male SWD which are easy to identify due to their spotted wings, and able to predict fruit infestation from trap captures. Deli-cup-based liquid traps (grower standard), which make in-situ observations difficult, were compared with red-panel sticky traps, both baited with commercial lures (Scentry, Trécé Broad-Spectrum (BS), and Trécé High-Specificity (HS)), across several US states in blueberries (lowbush and highbush), blackberry, raspberry, and cherry crops during 2018 and 2021. Results showed that red-panel traps effectively captured SWD, were able to detect male SWD early in the season while also being selective to male SWD all season-long, and in some cases linearly related male SWD trap captures with fruit infestation. Scentry and Trécé BS lures captured similar numbers of SWD, though Trécé BS and Trécé HS were more selective for male SWD in red panel traps than liquid traps in some cases. In conclusion, due to its ease of use with less processing time, red-panel traps are promising tools for detecting and identifying male SWD in-situ and for predicting fruit infestation. However, further research is needed to refine the trap captures and fruit infestation relationship and elucidate the trap-lure interactions in berry and cherry crops.

Effects of Three Cultural Practices on Drosophila suzukii (Diptera: Drosophilidae) in Open Blueberry Fields in Florida

The spotted-wing Drosophila (SWD), Drosophila suzukii, is native species in Southeast Asia. For over a decade, this invasive pest has been globally expanding. The economic losses to soft fruits and stoned fruits in the United States are increasing every year. Presently, the only viable tool to reduce the SWD population is the continued use of broad-spectrum insecticides. Pesticide resistance is appearing in the populations for the SWD. Organic farmers have limited options to control this pest in open fields. The major goal of this study was to develop cost-effective pest management strategies to manage the SWD using three types of mulches (two plant-based and one fabric-based) to reduce fly population and damage in open blueberry fields in north Florida. The study was conducted in two fruiting seasons (2017 and 2018). The study results demonstrated that the fly trap catches in 2017 shortleaf pine needle mulch had much higher populations (about 2.5-fold) of the SWD than all other treatments. In 2018, the numbers were about 1.7-fold more on shortleaf pine needle mulch than on other treatments. The fine texture of the mulch (pine needles) can easily facilitate the emergence of the SWD if the mulch is not thick enough. Although the pine needles covered the soil surface, it may have been too thin and thus allowed the SWD adults to emerge from the soil without much hindrance. In 2018, a higher population of the SWD was recorded from all the mulching practices. However, there were no significant differences in trap catches between all treatments. In general, the fly population is reduced with the use of pine bark and black weed fabric mulches. This is the first study that reports the effects of three mulches in controlling the SWD populations, which could benefit conventional and organic blueberry growers.

Monitoring of Spotted-Wing Drosophila (Diptera: Drosophilidae) Resistance Status Using a RAPID Method for Assessing Insecticide Sensitivity Across the United States

Drosophila suzukii (Matsumura) has spread rapidly, challenging berry and cherry crop production due to its ability to lay eggs into ripening fruit. To prevent infestation by this pest, insecticides are applied during fruit ripening and harvest. We field-tested the Rapid Assessment Protocol for IDentification of resistance in D. suzukii (RAPID) on seventy-eight populations collected across eight U.S. states in 2017 and 2018. Exposure to LC50 rates of malathion, methomyl, spinetoram, spinosad, and zeta-cypermethrin led to average female fly mortality of 25.0% in 2017, and after adjusting concentrations the average was 39.9% in 2018. Using LC99 × 2 discriminating concentrations in 2017 and LC90 × 8 rates in 2018, average female mortalities were 93.3% and 98.5%, respectively, indicating high overall susceptibility. However, using these high concentrations we found 32.0% of assays with survival of some female flies in 2017 and 27.8% in 2018. The adjustment in discriminating dose from 2017 to 2018 also reduced the proportion of assays with <90% survival from 17.6 to 2.9%. Populations with low mortality when exposed to spinosad were identified using this assay, triggering more detailed follow-up bioassays that identified resistant populations collected in California coastal region berry crops. Widespread evaluations of this method and subsequent validation in California, Michigan, and Georgia in 2019-2021 show that it provides a quick and low-cost method to identify populations of D. suzukii that warrant more detailed testing. Our results also provide evidence that important insecticide classes remain effective in most U.S. regions of fruit production.

Within-plant Distributions and Density of Amblyseius swirskii (Acari: Phytoseiidae) as Influenced by Interactions Between Plastic Mulch and Vegetable Crop Species

Plastic mulch of different colors and ultraviolet (UV) reflectivity individually or combined with released arthropod predators is an important component of an integrated pest management strategy. In 2015 and 2016, we evaluated the density and within-plant distribution of a released predatory mite, Amblyseius swirskii Athius-Henriot (Acari: Phytoseiidae) in snap bean (Phaseolus vulgaris L.), cucumber (Cucumis sativus L.), yellow squash (Cucurbita pepo L.), eggplant (Solanum melongena L.), Jalapeno pepper (Capsicum annuum L.), and tomato (Solanum lycopersicum L.) grown on different plastic mulches. The mulch treatments evaluated were: metalized top and black bottom, metalized top and white bottom, black-on-black, black-on-white, white-on-black, and bare soil with no mulch. Crop species had a significant effect on the density of A. swirskii. Eggplant and cucumber had higher numbers of A. swirskii than the other crops tested in 2015. In 2016, the density of A. swirskii was higher on eggplant than on cucumber. There was a variation in the distribution of A. swirskii in different strata of the plant canopies with the highest number in the bottom stratum of each crop, which was positively correlated with the population of Thrips palmi Karny (Thysanoptera: Thripidae). Mulch type had no effect on the density or distribution of A. swirskii in any strata of any of the crops tested. The results of this study indicate that releasing A. swirskii is compatible with the use of UV-reflective mulch. This information about host preference and within-plant distribution of A. swirskii should be of value in pest management programs for the crops studied.

The Effect of Summer Cover Crops and Strawberry Cultivars on the Twospotted Spider Mite, Tetranychus urticae (Acari: Tetranychidae) and the Predatory Mite, Neoseiulus californicus (Acari: Phytoseidae) in Organic Strawberry Production Systems in Florida

The twospotted spider mite, Tetranychus urticae (Koch) (Acari: Tetranychidae), is a key pest of strawberries and many other crops worldwide. Cover cropping, selecting tolerant or resistant cultivars, and biological control are important strategies of an organic management plan. In this study, we examined the effect of summer cover crops and strawberry cultivars on populations of T. urticae and a commercially available predatory mite, Neoseiulus californicus McGregor (Acari: Phytoseiidae), commonly used for T. urticae management in Florida. In the 2013-2014 season, four cover crops and eight strawberry cultivars were screened at the research station and on a commercial organic strawberry farm. The following season, the most promising cover crops (sunn hemp and hairy indigo) and cultivars, 'Sensation', 'Strawberry Festival', and 'Winterstar' were tested at the research station and on two small organic farms. In the 2016-2017, 2017-2018, and 2018-2019 seasons, a 4-way mix of cover crops was compared to sunn hemp and hairy indigo. In 2016-2017, 'Florida Radiance' was added to the three previously selected cultivars. 'Florida Beauty' replaced 'Strawberry Festival' in 2017-2018 and 2018-2019, and 'Florida Brilliance' replaced 'Winterstar' in 2018-2019. The effects of summer cover crops on both T. urticae and N. californicus were minimal. 'Florida Brilliance', 'Florida Radiance', 'Sensation', 'Strawberry Festival', and 'Winterstar' had lower T. urticae populations and higher yields in most seasons at most locations. The establishment and abundance of N. californicus was similar on these cultivars and was generally higher where T. urticae populations were higher. Implications for organic strawberry production in Florida are discussed.

Sex-Dependent Effects of the Microbiome on Foraging and Locomotion in Drosophila suzukii

There is growing evidence that symbiotic microbes can influence multiple nutrition-related behaviors of their hosts, including locomotion, feeding, and foraging. However, how the microbiome affects nutrition-related behavior is largely unknown. Here, we demonstrate clear sexual dimorphism in how the microbiome affects foraging behavior of a frugivorous fruit fly, Drosophila suzukii. Female flies deprived of their microbiome (axenic) were consistently less active in foraging on fruits than their conventional counterparts, even though they were more susceptible to starvation and starvation-induced locomotion was notably more elevated in axenic than conventional females. Such behavioral change was not observed in male flies. The lag of axenic female flies but not male flies to forage on fruits is associated with lower oviposition by axenic flies, and mirrored by reduced food seeking observed in virgin females when compared to mated, gravid females. In contrast to foraging intensity being highly dependent on the microbiome, conventional and axenic flies of both sexes showed relatively consistent and similar fruit preferences in foraging and oviposition, with raspberries being preferred among the fruits tested. Collectively, this work highlights a clear sex-specific effect of the microbiome on foraging and locomotion behaviors in flies, an important first step toward identifying specific mechanisms that may drive the modulation of insect behavior by interactions between the host, the microbiome, and food.

Spatio-Temporal Distribution and Fixed-Precision Sampling Plan of Scirtothrips dorsalis (Thysanoptera: Thripidae) in Florida Blueberry

Scirtothrips dorsalis Hood is an invasive and foliar pest of Florida blueberry that reduces plant growth by feeding on new leaf growth. A sampling plan is needed to make informed control decisions for S. dorsalis in blueberry. Fourteen blueberry fields in central Florida were surveyed in 2017 and 2018 after summer pruning to determine the spatial and temporal distribution of S. dorsalis and to develop a fixed-precision sampling plan. A sampling unit of ten blueberry shoots (with four to five leaves each) was collected from one blueberry bush at each point along a 40 × 40 m grid. Field counts of S. dorsalis varied largely ranging from zero to 1122 adults and larvae per sampling unit. Scirtothrips dorsalis had aggregated distribution that was consistent within fields and temporally stable between summers, according to Taylor's power law (TPL) (aggregation parameter, b = 1.57), probability distributions (56 out of 70 sampling occasions fit the negative binomial distribution), Lloyd's index (b > 1 in 94% occasions), and Spatial Analysis by Distance IndicEs (31% had significant clusters). The newly developed fixed-precision sampling plan required 167, 42, seven, or three sampling units to estimate a nominal mean density of 20 S. dorsalis per sampling unit with a precision of 5%, 10%, 25%, or 40%, respectively. New knowledge on S. dorsalis distribution will aid in evaluating the timing and effectiveness of control measures.

The Short-Range Movement of Scirtothrips dorsalis (Thysanoptera: Thripidae) and Rate of Spread of Feeding Injury Among Strawberry Plants

Scirtothrips dorsalis Hood infest strawberry (Fragaria x ananassa Duchesne, Rosaceae) fields from nearby crop fields and surrounding vegetation and cause injury to plants by feeding on young leaf tissues. Greenhouse and field studies were conducted to determine the short-range movement of S. dorsalis to assess the risk of an early S. dorsalis population to spread to adjacent plants. In a greenhouse, 25 potted strawberry plants were arranged in two concentric rows around a central plant, where plants in inner rows were 20 cm, and those in the outer rows were 40 cm from the central plant. In the field, 20 strawberry plants were arranged in two beds (90 cm apart), ten in each bed, and five plants in each row, with plants 30 cm apart. White sticky cards were placed at 60-120 cm from the central plant. Fifty S. dorsalis adults were released on a centrally located plant, and the numbers of S. dorsalis adults and larvae and feeding injury were recorded for 9-17 d on adjacent plants and sticky cards. Results showed that significantly more S. dorsalis adults and larvae remained on the initially infested plant compared to adjacent plants, although few adults were found up to 120 cm on sticky cards. The rate of spread of feeding injury was low with slight bronzing injury (<10% injury) on adjacent plants by 14-17 d. Since most S. dorsalis remained on initially infested plants for at least 2 wk, it is feasible to delay management actions and 'rescue' plants around a plant with minor injury symptoms.

Effect of Cultural Practices on Neopamera bilobata in Relation to Fruit Injury and Marketable Yields in Organic Strawberries

Simple Summary

The strawberry seed bug is a native insect that has recently been causing injury to strawberries in Florida. This study examined the effects of two common cultural practices on the strawberry seed bug: cover cropping and runner removal. Cover cropping is used only in organic strawberry production while runner removal is common to both production systems. The effects of cultivar were also examined. Lastly, small bags were tied around strawberry fruits and different numbers of nymphal and adult seed bugs were released into the bags to examine the effects of their feeding on strawberry fruits. The use of cover crops did not impact seed bug populations. The results for runner removal were inconsistent but it was clear that removing runners does not increase seed bug populations or their injury to fruit. The cultivar “Florida Brilliance” received less injury likely because its seeds are recessed in the flesh of the fruit, making them more difficult for seed bugs to access. Both adults and nymphs caused injury to ripe fruit. Adults did not feed on unripe fruit, so injury to unripe fruit is likely caused by nymphal feeding.

Abstract

The strawberry seed bug, Neopamera bilobata (Say), is an emerging pest of organic and conventional strawberries in Florida. There is limited information on this Rhyparochromidae species. Thus, the type of injury caused is not clearly documented and management recommendations are lacking. In this study, we evaluated the effect of strawberry cultivars, cover crops, and the presence of runners on N. bilobata populations and yield. We also investigated the effect of select cultivars and the presence of runners on N. bilobata injury levels. In addition, we used fruit bagging experiments to investigate the effects of N. bilobata population and life stage (nymph vs. adult) on strawberry fruits. There was no effect of cover crop or cultivar on N. bilobata populations. In the 2017–2018 season, strawberry plots with runners contained higher N. bilobata populations compared with plots without runners, and adult infestation was significantly higher than nymphal infestation. In the 2018–2019 season, the trend was reversed with higher numbers of N. bilobata collected in plots with runners removed. In the 2019–2020 season, there was no significant difference in N. bilobata populations in plots with and without runners. In both 2018–2019 and 2019–2020, nymphal infestation was higher than adult infestation. Less injury was recorded in “Florida Brilliance” compared with the other cultivars tested. In the 2019–2020 season, less injury was recorded from plots without runners while the difference was not significant in 2017–2018 or 2018–2019. Releasing five and ten adult N. bilobata on ripe (red) fruit produced a similar level of injury while no injury to unripe (green) fruit was observed. Both adults and nymphs cause injury to ripe fruit. These findings can help contribute to the development of an integrated pest management program for strawberry N. bilobata.

Distribution Pattern of Thrips (Thysanoptera: Thripidae) and Tomato Chlorotic Spot Virus in South Florida Tomato Fields

Tomato chlorotic spot virus (TCSV) is an orthotospovirus that causes a devastating disease in tomato (Lycopersicon esculentum Miller). TCSV emerged recently in South Florida. Studies were conducted in three commercial tomato fields in Miami-Dade County, Florida during the vegetable-growing seasons from October to April in 2015 through 2017. Each year, data were collected at 3, 6, and 9 wk after transplanting at various distances from the edges of each fields. Based on 3 yr total samples, three species of thrips were commonly observed melon thrips, Thrips palmi Karny (62.16 ± 0.79%), being the most abundant species followed by common blossom thrips, Frankliniella schultzei Trybom (21.55 ± 0.66%), and western flower thrips, Frankliniella occidentalis (Pergande) (16.26 ± 0.61%). Abundance of all thrips and TCSV infected plants was high at the edge of a tomato field 3 wk after transplanting with significantly fewer infected plants toward the center of the field. The distribution patterns of thrips and TCSV in various fields were mostly regular and aggregated across the sampling dates during the study period. Abundance of TCSV symptomatic plants and thrips species was high at the edge of the field and increased over time. The number of samples required to accurately determine population density of thrips was calculated by using three precision levels (0.10, 0.20, 0.30) at three predetermined densities of thrips (0.10, 0.20, and 0.40 per sample). This information will provide guidelines to growers, crop protection personnel, agricultural scouts, and researchers to develop a sustainable thrips and tospovirus management program.

Evaluation of Monitoring Traps and Lures for Drosophila suzukii (Diptera: Drosophilidae) in Berry Plantings in Florida

Drosophila suzukii (Diptera: Drosophilidae) is an invasive insect pest that was detected in Florida in August 2009 in Hillsborough County. Very limited information is available for berry growers to properly detect and monitor this serious pest in southern highbush blueberry (hybrids of Vaccinium corymbosum L. × V. darrowi Camp), rabbiteye blueberry (Vaccinium virgatum L.), and blackberry (Rubus fruticosus L.) production systems. We compared several D. suzukii traps and lures/baits at two sites in Florida. The traps evaluated included Trécé, Scentry, and a standard homemade cup trap. These traps were compared with various baits and lures, including Trécé lure, Scentry lure, yeast bait, and Suzukii trap, under Florida production systems. Early detection is important to develop an effective monitoring system so management action can be taken before economic damage occurs. Data were recorded as overall trends, as well as in 4–5 trapping periods from early to late season. Overall, the Scentry trap baited with Scentry lure, the Trécé trap baited with Trécé lure + yeast, and the Trécé trap baited with Scentry lure were the best performing traps. Yeast-based traps were also attractive to D. suzukii early in the season, but they did not provide consistent captures as the season progressed. The Scentry trap with yeast bait, the Scentry trap with Scentry lure, the Trécé trap with Trécé lure + yeast bait, and a cup trap with yeast bait caught most of the flies during the first trapping period in 2015 and 2016 in the rabbiteye blueberry. In the southern highbush blueberry, the population of D. suzukii was much lower than in the rabbiteye blueberry planting, and the Scentry trap with Scentry lure captured the highest number of flies during the first trapping period in 2016. In the blackberry, the Scentry trap with Scentry lure numerically had the highest captures during the first trapping period, but this was not significantly different from the cup trap with yeast bait, the Trécé trap baited with Suzukii trap, and the Trécé trap with Trécé lure. Overall, the Scentry trap with Scentry lure was the most consistent trap that captured D. suzukii flies throughout the season in the three production systems—rabbiteye blueberry, southern highbush blueberry, and blackberry. Growers in low pressure systems that are similar to Florida can use the Scentry trap with Scentry lure to monitor D. suzukii populations.

Host Preference and Plastic Mulches for Managing Melon Thrips (Thysanoptera: Thripidae) on Field-Grown Vegetable Crops

Melon thrips, Thrips palmi Karny (Thysanoptera: Thripidae), is a serious pest of vegetable, ornamental, and fruit crops. As a potential component of an integrated pest management (IPM) program, different plastic mulches including white-on-black, black-on-white, black-on-black, two metalized ultraviolet (UV)-reflective mulches, and a no mulch control were evaluated for managing T. palmi on six field-grown vegetable crops (eggplant, cucumber, squash, snap bean, Jalapeno pepper, and tomato) during the Fall of 2015 and 2016. Metalized reflective mulch significantly reduced the number of T. palmi in all vegetable crops compared with the other treatments. The highest numbers of T. palmi were observed on the white-on-black mulch and control treatments. The numbers of adults and larvae were highest on eggplant followed by cucumber, snap bean, squash, and Jalapeno pepper. The lowest numbers of T. palmi were observed on tomato plants. This study indicated that growing vegetable crops on metalized mulch is an effective method of reducing T. palmi populations in vegetable crops and should be considered in IPM programs for this insect species.

Multistate Comparison of Attractants and the Impact of Fruit Development Stage on Trapping Drosophila suzukii (Diptera: Drosophilidae) in Raspberry and Blueberry

Spotted-wing drosophila, Drosophila suzukii Matsumura (Diptera: Drosophilidae), is an invasive pest of soft-skinned fruits across the globe. Effective monitoring is necessary to manage this pest, but suitable attractants are still being identified. In this study, we combined lures with fermenting liquid baits to improve D. suzukii trapping specificity and attractiveness. We also measured the efficiency and specificity of baits/lures during different times of the season; the reproductive status of females among baits/lures; and the effects of locations and crop type on these response variables. We developed a metric that combined mating status and fat content to determine differences in types of females attracted. Lures utilizing yeast and sugar-based volatiles trapped the most D. suzukii. The addition of a commercial lure to yeast and sugar-based lures increased catches in most locations, but was also the least specific to D. suzukii. Apple juice-based chemical lures tended to be most specific to D. suzukii, while lures comprised of a singular attractant tended to trap more D. suzukii with a higher reproductive potential than combinations of attractants. Trap catch and lure specificity was lower during fruit development than fruit ripening. While catch amounts varied by geographic location and crop type, attractants performed similarly relative to each other in each location and crop. Based on the metrics in this study, the yeast and sugar-based attractants were the most effective lures. However, further work is needed to improve early season monitoring, elucidate the effects of physiological status on bait attraction, and understand how abiotic factors influence bait attraction.

Trapping system comparisons for and factors affecting populations of Drosophila suzukii and Zaprionus indianus in winter-grown strawberry

BACKGROUND

Drosophila suzukii (Matsumura) is a major fruit pest in temperate regions worldwide, but in subtropical Florida, winter-grown strawberries have not been severely affected. Zaprionus indianus Gupta is another invasive drosophilid species and a pest of some tropical fruits. To improve monitoring, trapping systems for D. suzukii and Z. indianus were tested. Morphology, ovarian status and the suitability and availability of non-crop hosts as possible D. suzukii population-limiting factors were assessed.

RESULTS

Traps with commercial attractants captured more D. suzukii but fewer Z. indianus than those with a homemade mixture. In central and northern Florida, < 10% and 30-80% of D. suzukii, respectively, exhibited darker, winter morph coloration, and 55-75% of females from central Florida were carrying mature and/or immature eggs. Adult D. suzukii were reared from fruits of two of 28 potential hosts: elderberry (Sambucus nigra) and nightshade (Solanum americanum). Nightshade, but not elderberry, was common on field perimeters (21 and six of 36 fields, respectively). Traps placed in wooded or partially wooded field edges yielded the most D. suzukii.

CONCLUSION

Florida strawberry is at risk of D. suzukii infestation, as flies were captured throughout the growing season. However, fly captures remained relatively low, peaking at 1.5 flies per trap per day. In central Florida, the low availability and suitability of non-crop hosts likely limit population growth. The finding of few flies in northern Florida may additionally be attributable to a greater proportion of flies displaying winter morph coloration than in central Florida. © 2018 Society of Chemical Industry.

Evaluation of site-specific tactics using bifenazate and Neoseiulus californicus for management of Tetranychus urticae (Acari: Tetranychidae) in strawberries

Greenhouse and field experiments were conducted to evaluate the effectiveness of site-specific tactics for management of the twospotted spider mite, Tetranychus urticae Koch, a major pest of greenhouse and field-grown strawberries (Fragaria x ananassa Duchesne). Two site-specific (spot) treatments, the miticide bifenazate (Acramite(®)) and the predatory mite Neoseiulus californicus McGregor, were compared with whole-plot treatments of bifenazate or N. californicus to determine whether T. urticae could be effectively managed in field-grown strawberry using only site-specific tactics. Additionally, the cost of site-specific tactics was compared with whole-plot treatments to determine the economic value of using site-specific management tactics for T. urticae in strawberries. In the greenhouse, all treatments equivalently reduced the number of T. urticae below control. In the field during the 2011-2012 season, more T. urticae eggs and motiles were in the whole-plot treatments of both N. californicus and bifenazate in the mid-season and late season, respectively, compared with the spot treatments. With the exception of site-specific N. californicus during the 2011-2012 field season, there were no differences in marketable yields between plots with site-specific treatments and whole-plot management. An economic analysis demonstrated a significant cost savings (75.3 %) with site-specific treatments of N. californicus compared with whole-plot application of N. californicus. Similarly, a 24.7 % reduction in cost was achieved in using site-specific bifenazate compared with whole-plot application of bifenazate. The findings indicate that site-specific treatments with N. californicus and bifenazate are competitive alternatives to whole-field application for T. urticae management in strawberries.

Evaluation of Bioinsecticides for Management of Bemisia tabaci (Hemiptera: Aleyrodidae) and the Effect on the Whitefly Predator Delphastus catalinae (Coleoptera: Coccinellidae) in Organic Squash

Organic zucchini squash is a high-value vegetable crop in Florida and potential exists to expand its production throughout the state. A lack of knowledge on the effectiveness of organic products and their integration with natural enemies is an important constraint to the regulation of pest populations in organic squash production in Florida. The objectives of this study were to evaluate the effect of insecticides labeled for organic production that can be used for management of Bemisia tabaci (Gennadius) biotype B, on organically grown squash; and to determine the effects of the most efficient insecticides on a key natural enemy, Delphastus catalinae (Horn). Experiments were conducted in the greenhouse in exclusion cages. The first experiment compared the effects of four bioinsecticides on whitefly densities. Insecticides include 1) AzaSol (azadirachtin), 2) PyGanic EC 1.4 (pyrethrin), 3) M-Pede (insecticidal soap), and 4) Entrust (spinosad). The second experiment investigated the effects of bioinsecticides on D. catalinae Treatment effectiveness was evaluated 1, 3, and 5 d posttreatment. PyGanic and M-Pede were highly effective in controlling whitefly populations on organic squash, while moderate control was provided by AzaSol and there was no control provided by Entrust. PyGanic and M-Pede treatments reduced D. catalinae populations when adults were released 1 d post pesticide application. However, when adults were released 5 d post application, there was no reduction. The importance of using bioinsecticides in combination with natural enemies to regulate pest populations in organic cropping systems is discussed.

Preference of Bemisia tabaci biotype B on zucchini squash and buckwheat and the effect of Delphastus catalinae on whitefly populations

BACKGROUND

Zucchini squash, Cucurbita pepo L., is an important vegetable crop in Florida. Physiological disorders and insect-transmitted diseases are major problems for squash growers in semi-tropical regions around the world. Bemisia tabaci (Gennadius) biotype B is a significant whitefly pest and is largely responsible for transmitting viruses and causing physiological disorders in squash. Several studies have shown that whitefly populations are reduced when crops are interplanted with non-host cover crops or mulches. The aim of the present study was to determine how the presence of buckwheat, Fagopyrum esculentum Moench, and a key predator, Delphastus catalinae (Horn), affect whitefly colonization on squash.

RESULTS

Whitefly densities were higher on squash than on buckwheat. The introduction of D. catalinae on squash significantly reduced whitefly populations. Overall, there were higher densities of D. catalinae on squash where the whitefly pest was more concentrated compared with buckwheat.

CONCLUSION

The study provided preliminary evidence that D. catalinae, when used in conjunction with buckwheat as a living mulch, may aid in reducing whiteflies in squash. This greenhouse experiment highlights the need to investigate a multitactic approach of intercropping buckwheat with squash and the incorporation of D. catalinae in the field to manage populations of whiteflies and whitefly-transmitted diseases. © 2015 Society of Chemical Industry.

Effect of trap design, bait type, and age on captures of Drosophila suzukii (Diptera: Drosophilidae) in berry crops

Field experiments were conducted in commercial southern highbush blueberries and wild blackberries to evaluate the attractiveness of different trap designs, bait types, and bait age on captures of the spotted wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae). During the 2012 trap design study, the five treatments evaluated were four 1-liter clear plastic cup traps (with and without a yellow visual stimulus or odorless dish detergent) and the fifth treatment was a Pherocon AM yellow sticky card trap. Cup traps were baited with 150 ml of apple cider vinegar (ACV) and the Pherocon AM trap had a 7.4-ml glass vial containing ACV. In 2013, the Pherocon AM yellow sticky card was omitted because of low spotted wing drosophila captures in 2012. The four treatments evaluated were four 1-liter cup traps with and without a yellow visual stimulus. One cup trap (with a yellow stimulus) was baited with yeast + sugar in place of ACV and the other cup traps were baited with ACV. In both years, there were no differences in spotted wing drosophila captures among cup traps baited with ACV with and without yellow visual stimulus. However, the cup trap baited with yeast + sugar and yellow visual stimulus captured more spotted wing drosophila than the ACV-baited cup traps irrespective of visual stimulus or detergent. In another study, four baits including 1) ACV, 2) yeast + sugar mixture, 3) yeast + flour mixture (yeast, sugar, water, whole wheat flour, and ACV), and 4) wine + vinegar mixture (rice vinegar and merlot wine) were evaluated in a commercial blueberry planting using 1-liter clear plastic cup traps (as described above). The experiment was repeated in wild blackberries but the yeast + flour bait was replaced with ACV + merlot wine + sugar. Results indicated that the two yeast baits captured significantly more spotted wing drosophila and more nontarget organisms than the vinegar baits. In the final study, although we found that the attraction of ACV and yeast + sugar to spotted wing drosophila did not change with bait age, the attraction to other Drosophilidae flies decreased with age. The ease of implementing a trap-and-lure system for spotted wing drosophila is discussed.

Field distribution of Dasineura oxycoccana (Diptera: Cecidomyiidae) adults, larvae, pupae, and parasitoids and evaluation of monitoring trap designs in Florida

Blueberry gall midge, Dasineura oxycoccana (Johnson), is a pest of cultivated blueberries throughout the world. Larvae feed and develop in developing leaf buds, and also in flower buds of rabbiteye blueberries, which causes buds to fall off the plant. These injuries can cause up to 80% yield loss in heavy infestations. As the larvae are protected from insecticides, adults must be targeted with foliar applications. Consequently, the detection of adults through an effective monitoring program is critical to time insecticide sprays against the blueberry gall midge. Understanding the distribution of the midge and its parasitoids is also important information for developing a more effective pest management program. A comparison of three monitoring trap types demonstrated that bucket emergence traps and clear panel traps captured similar numbers of midges, although the bucket trap is more sensitive at low population levels. Using bucket emergence traps, we found that nearly 80% of the midges collected pupated within 48 cm of the blueberry bush, suggesting that a targeted soil treatment may be a viable integrated pest management tactic that could be included in a midge management program. Traps and bud samples demonstrated that adult and larval midges and parasitoids were randomly distributed throughout the field in both years, with the exception of larval aggregation in early 2012. As parasitoid distribution is parallel to host occurrence within blueberry plantings, this increases the potential for biological control activities against the blueberry gall midge in fields that do not receive broad-spectrum insecticide applications.

Effect of Tetranychus urticae (Acari: Tetranychidae), on marketable yields of field-grown strawberries in north-central Florida

Understanding the impact of a pest species on a particular crop is critical for the success of a pest management program. Field studies were conducted to determine the effect of the twospotted spider mite, Tetranychus urticae Koch, on marketable yield of strawberries during the 2008/2009 and 2009/2010 growing seasons. Low, medium, and high mite infestation levels were established by initial inoculations of5, 10, and 20 twospotted spider mites per strawberry leaf, respectively. A control treatment maintained at near zero mites through applications of an acaricide, bifenazate (Acramite 50 WP), was also included. Weekly records of motile twospotted spider mites were obtained over 13 and 16 wk during the 2008/2009 and 2009/2010 growing seasons, respectively. Degree-days and weather parameters were monitored to determine their effect on mite population. In addition, mite-days were calculated for each year from weekly mite counts to determine the effect of mites on marketable yield of strawberries. In both years, twospotted spider mite population increased throughout the growing seasons. More degree-days were accumulated during the 2008/2009 growing season, and mite population was higher in 2008/2009 than in 2009/2010. Mite population density per leaf increased up to 278 motiles per leaf in 2008/2009 growing season as compared with 137 in 2009/2010 within the high-infestation-level treatment. The divergence in mite population between the two growing seasons was attributed mainly to temperature differences between the two seasons that affected mite population development and establishment. During both growing seasons, the high mite infestation level had lowest marketable yield. A negative correlation between cumulative mite-days and harvested marketable yields was detected in both seasons, but it was only significant during the 2008/2009 growing season. Strawberry yield reduction was detected when plants attained 80 mites per leaf in 2008/2009 and 50 mites per leaf in 2009/2010 within the high mite infestation treatment. Factors that affect mite population establishment and management for twospotted spider mites on strawberries are discussed.

Parasitism of Dasineura oxycoccana (Diptera: Cecidomyiidae) in North Central Florida

Blueberry gall midge, Dasineura oxycoccana (Johnson), is a key pest of blueberries in Florida. As a larva, this insect feeds in developing flower and leaf buds. Management of D. oxycoccana relies principally on chemical insecticides; however, efficacy is limited because D. oxycoccana is sheltered within the plant during most of its life cycle. Natural enemies, particularly parasitoids, may play an important role in regulating D. oxycoccana populations. To determine the seasonal dynamics and parasitism rates of eulophid and platygastrid wasps parasitizing D. oxycoccana larvae, we sampled D. oxycoccana larvae by collecting infested blueberry leaf buds from a minimally-managed farm in north central Florida. Midge larvae were examined under a microscope to determine parasitism status of host instars. Parasitism rates ranged from 25 to 40% over the 3-yr study. Percent parasitization was significantly higher in third instars than first or second instars. Midge larvae in the centers of leaf buds were significantly less likely to be parasitized than larvae in outer layers of leaf buds. Thirty-seven percent of midge larvae had been parasitized multiple times, suggesting these parasitoids do not discriminate between parasitized and unparasitized hosts. Implications for pesticide use in relation to the conservation of natural enemies and management of D. oxycoccana populations are discussed.

Species composition, monitoring, and feeding injury of stink bugs (Heteroptera: Pentatomidae) in blackberry

Blackberry (Rubus spp.) production in Florida has increased > 100% within the past two decades. and several insect pests, including stink bugs (Heteroptera: Pentatomidae), have been observed feeding on this crop. The objectives for this study were to determine the stink bug species present in blackberry; to develop monitoring tools for stink bugs in blackberry; and to describe feeding injury to blackberries by Euschistus quadrator Rolston, a relatively new stink bug pest to Florida, that has spread throughout the state. In a field survey, E. quadrator was the most abundant stink bug species, followed by Euschistus servus Say, Euschistus obscurus (Palisot de Beauvois), Thyanta custator (F.), Proxys punctulatus (Palisot de Beauvois), and Podisus maculiventris Say. Yellow pyramid traps caught more stink bugs than tube traps with or without the addition of Euschistus spp. pheromone lures. There were no statistical differences between traps baited with a Trécé Pherocon Centrum lure, a Suterra Scenturion lure, and an unbaited trap. These results were supported by Y-tube olfactometer assays with E. quadrator where there were no differences between pheromone baited lures and a control. Injury to berries caused by E. quadrator adults and third instars was similar, and both adults and third instars fed more on green berries compared with turning berries. In addition, adults fed more on green berries compared with ripe fruit. The most common injury to green berries was discoloration. In contrast, misshapen drupelets were commonly seen on turning and ripe berries. The potential for managing stink bugs in blackberries to prevent them from reaching damaging levels is discussed.

Biology and efficacy of Aprostocetus (Eulophidae: Hymenoptera) as a parasitoid of the blueberry gall midge complex: Dasineura oxycoccana and Prodiplosis vaccinii (Diptera: Cecidomyiidae)

In the southeastern United States, bud-infesting larvae of two gall midge species, Dasineura oxycoccana (Johnson) and Prodiplosis vaccinii (Felt), destroy from 20 to 80% of the rabbiteye blueberry crop, Vaccinium virgatum Aiton (syn. V. ashei Reade). These midge larvae are attacked by five species of parasitoid wasps. The most effective of these is the bivoltine eulophid Aprostocetus sp. nr. marylandensis (Eulophidae), whose adults constitute one-third of the gall midge parasitoids, active in both conventional and organic blueberry fields. Broods of Aprostocetus use several reproductive strategies to keep sole possession of their larval hosts. As solitary endoparasitoids as well as facultative hyperparasitoids, precocial larvae of Aprostocetus devour hosts organs along with any younger siblings and rival parasitoid broods. Although larger hosts are preferred, any sized larvae can be parasitized, which reduces brood congestion and infanticide. An Aprostocetus female spends an hour or more in a systematic hunt for hosts, during which time 40 to 100% of midge larvae encountered are parasitized. Aprostocetus females could have located hosts more quickly had they recognized host-feeding scars as cues. Even so, high rates of larval parasitism achieved by Aprostocetus may kill as many midges as insecticides do.

Effects of southern highbush blueberry cultivar and treatment threshold on flower thrips populations

In Florida, southern highbush (SHB) blueberries (Vaccinium corymbosum L. x Vaccinium darrowi Camp) are grown for a highly profitable early season fresh market. Flower thrips are the key pest of SHB blueberries, and Frankliniella bispinosa (Morgan) is the most common species found. Flower thrips injure blueberry flowers by feeding and ovipositing in all developing tissues. These injuries can lead to scarring of developing fruit. The objectives of this study were to determine the relationship between thrips and yield in different SHB blueberry cultivars and to determine an action threshold. Experiments were conducted during early spring 2007 and 2008 on four farms; a research farm in Citra, FL; and three commercial farms, two in Hernando Co., FL., and one in Lake Co., FL. At the Citra farm, 'Emerald', 'Jewel', 'Millennia', and 'Star' blueberries were compared in 2007, and all but Star were compared in 2008. On the Hernando and Lake Co. farms, two treatment thresholds (100 and 200 thrips per trap) and an untreated control and four cultivars (Emerald, Jewel, Millennia, and 'Windsor') were compared. Emerald consistently had more thrips per trap and per flower than the other cultivars on all four farms. However, this did not always lead to an increase in fruit injury. Thrips numbers exceeded the threshold on only one farm in 2007, and there was a significantly lower proportion of injured and malformed fruit in the 100 thrips per trap threshold treatment compared with the control on this farm.

Examining the spatial distribution of flower thrips in southern highbush blueberries by utilizing geostatistical methods

Flower thrips (Frankliniella spp.) are one of the key pests of southern highbush blueberries (Vaccinium corymbosum L. x V. darrowii Camp), a high-value crop in Florida. Thrips' feeding and oviposition injury to flowers can result in fruit scarring that renders the fruit unmarketable. Flower thrips often form areas of high population, termed "hot spots", in blueberry plantings. The objective of this study was to model thrips spatial distribution patterns with geostatistical techniques. Semivariogram models were used to determine optimum trap spacing and two commonly used interpolation methods, inverse distance weighting (IDW) and ordinary kriging (OK), were compared for their ability to model thrips spatial patterns. The experimental design consisted of a grid of 100 white sticky traps spaced at 15.24-m and 7.61-m intervals in 2008 and 2009, respectively. Thirty additional traps were placed randomly throughout the sampling area to collect information on distances shorter than the grid spacing. The semivariogram analysis indicated that, in most cases, spacing traps at least 28.8 m apart would result in spatially independent samples. Also, the 7.61-m grid spacing captured more of the thrips spatial variability than the 15.24-m grid spacing. IDW and OK produced maps with similar accuracy in both years, which indicates that thrips spatial distribution patterns, including "hot spots," can be modeled using either interpolation method. Future studies can use this information to determine if the formation of "hot spots" can be predicted using flower density, temperature, and other environmental factors. If so, this development would allow growers to spot treat the "hot spots" rather than their entire field.

Applications and mechanisms of wax-based semiochemical dispenser technology for disruption of grape root borer mating

Grape root borer, Vitacea polistiformis (Harris) (Lepidoptera: Sesiidae), is an important pest of cultivated grapes (Vitis spp.) in the eastern United States from Michigan to Florida. There are few registered insecticides for control of this pest, and their efficacy is limited. Pheromone-based mating disruption is a potential alternative to insecticides for management of V. polistiformis. Wax-based Specialized Pheromone & Lure Application Technology (SPLAT) was tested as a mating disruption method. Deployment densities of 150 dispensers per ha dosed with 5 mg of V. polistiformis pheromone were sufficient to achieve 95% mating disruption during a 7-wk trapping period. The disruption mechanism was determined to be competitive attraction. The release rate of pheromone from these dispensers was quantified to be approximately linear, 77.4 microg/g SPLAT/d. At this release rate, a minimum initial load of 5.4 mg of pheromone per dispenser would be needed to maintain disruption over a 9-10-wk V. polistiformis flight season, approximately 19 August to 21 October in central Florida. It should be noted, however, that the main pheromone component alone, (E,Z)-2,13-octadecadienyl acetate (ODDA), was effective (presumably by a noncompetitive mechanism) at higher loads per area of crop. Due to the cost of synthesis of highly pure isomers of the V. polistiformis pheromone components, mating disruption of V. polistiformis may be more practical with higher doses of commercially produced Zeuzera pyrina L. blend [95% (E,Z)-2,13-ODDA:5% (E,Z)-3,13-octadecadien-1-ol] or with (E,Z)-2,13-ODDA alone than with the V. polistiformis blend at lower rates.

Evaluation of emergence traps for monitoring blueberry gall midge (Diptera: Cecidomyiidae) adults and within field distribution of midge infestation

The blueberry gall midge, Dasineura oxycoccana (Johnson) (Diptera: Cecidomyiidae), is a key pest of rabbiteye blueberry, Vaccinium virgatum Aiton, in the southeastern United States, but it has not been studied extensively and little is known about its ecology and management. Studies were conducted to develop an improved method for monitoring D. oxycoccana adults and to determine the within-field distribution of infestation. Four emergence traps were evaluated in an organic rabbiteye blueberry planting for their effectiveness in capturing D. oxycoccana adults early in the season. These traps included a jar trap, wheat blossom midge trap, petri dish trap, and bucket trap. The petri dish and bucket traps captured the highest numbers of adults in 2007 and 2008, respectively. Both traps had a clear plastic panel coated with adhesive. Adult midges emerging from the soil beneath the traps were caught in the adhesive as they flew up toward the light. Emergence traps are useful for detecting the presence of adults early in the season before larval infestation is apparent in the flower buds. To determine the pattern of midge infestation, flower buds were collected weekly from January to March in 2006 from rabbiteye blueberry plants located in a plot at the southwest border of an existing blueberry planting. There were no differences found in the number of larvae collected from various distances within blueberry rows. However, when flower buds were collected from an isolated rabbiteye plot in 2007 and 2008, D. oxycoccana infestation was not uniform. In both years, the southern border row had a significantly higher number of midge larvae per bud compared with the other rows.

Visible/near infrared reflectance (VNIR) spectroscopy for detecting twospotted spider mite (Acari: Tetranychidae) damage in strawberries

The twospotted spider mite, Tetranychus urticae Koch, is among the most economically important pests in strawberries (Fragaria spp.). As T. urticae feeds, it ingests mesophyll cells that contain pigments essential for physiologic function and alters radiant energy use of the leaf tissue, severely compromising plant health and productivity. In our study, diffuse reflectance spectroscopy in the visible and near infrared (VNIR) portions of the spectrum was used to identify specific spectral regions altered by T. urticae feeding and to quantitatively assess T. urticae density. During the 2006-2007 growing season, 80 strawberry leaflets with varying levels of T. urticae infestation were collected. Spectral classification of both mite density (continuous) and mite density class (categorical) were developed. Spider mite density classes were low infestation (0-20 mites/leaflet), moderate infestation (20-50 mites/leaflet), and high infestation (> or = 50 mites/leaflet). Continuous spectral prediction for leaf infestation was developed using partial least squares (PLS) regression. Classification trees were used to train spectra to categorical levels of infestation. Both models were calibrated with 67% of the samples, and accuracy was evaluated using the remaining 33%. Categorical validation accuracy was 81%, with odds ratios for correctly predicting extreme categories (low and high) of 33 and 47.7, respectively. Continuous validation efficiency was also high, with an r2 between predicted and observed of 0.85 and a root-mean-squared error (RMSE) of 12.2 mites per leaf. Developing a spectral pest monitoring system would provide a diagnostic tool allowing early and effective intervention for precision management of T. urticae in strawberry.

Detection of Cucurbit leaf crumple virus in Florida Cucurbits

In October of 2006, yellow straightneck and zucchini squash plants (Cucurbita pepo L.) with crumpled, curled, thickened leaves were found in St. Johns and Marion counties in central Florida, respectively. Both locations had high populations of the whitefly, Bemisia tabaci. Incidences of symptomatic plants were greater than 95% in three squash fields (33 ha total) in St. Johns County and 35% in an experimental plot in Marion County. Twenty-three samples were collected from symptomatic plants (two from St. Johns County and 21 from Marion County). DNA was extracted for PCR and tested for the presence of begomoviruses using the following pairs of degenerate primers: AC1048/AV494, which amplifies a conserved region of the coat protein gene (2), PAR1c496/PAL1v1978, which amplifies a region of the begomovirus A component, and PBL1v2040/PCRc154, which amplifies a hypervariable region of the begomovirus B component (1). All squash samples yielded amplicons of sizes expected for a bipartite begomovirus: 1,159 nt with PAR1c496/PAL1v1978, 550 nt with AC1048/AV494, and 493 nt with PBL1v2040/PCRc154. The 1,159- and 493-nt amplicons obtained from two squash plants were cloned and sequenced. The 1,159 nt sequences from both plants shared 98% sequence identity with each other and 97% identity with equivalent regions of the A component of Cucurbit leaf crumple virus (CuLCrV) from Arizona and California (GenBank Accession Nos. AF256200 and AF224760, respectively). The 493-nt sequences amplified with PBL1v2040/PCRc154 were identical and shared a 96% identity with CuLCrV sequence (GenBank Accession No. AF327559) from Arizona and 97% identity with CuLCrV B component sequence (GenBank Accession No. AF224761) from California. Leaves were collected from eight symptomatic squash plants from Citra, FL and used for whitefly transmission assays. Approximately 100 adults of Bemisia tabaci biotype B were released onto each caged leaf and given a 24-h acquisition access period, after which a healthy squash seedling was introduced. Symptoms developed within 10 days on all test plants, and the presence of CuLCrV was confirmed by PCR assays, (primer pairs PAR1c496/PAL1v1978 and PBL1v2040/PCRc154) followed by sequencing. In 2007, similar symptoms were seen in several locations around the state. The same assays confirmed the presence of CuLCrV in watermelon (Citrullus lanatus L.) and squash in the following counties: Collier and Hendry in southwest Florida and Hillsborough, Manatee, and Sarasota in west-central Florida. To our knowledge, this is the first report of CuLCrV, and the first report of any begomovirus in cucurbits in Florida. References: (1) M. R. Rojas et al. Plant Dis. 77:340, 1993. (2) S. D. Wyatt and J. K. Brown. Phytopathology 86:1288, 1996.

Horizontal and vertical distribution of flower thrips in southern highbush and rabbiteye blueberry plantings, with notes on a new sampling method for thrips inside blueberry flowers

The dispersal behavior of flower thrips was studied during two field seasons within blueberry (Vaccinium spp.) plantings in Florida and southern Georgia. A "shake and rinse" technique used to extract thrips from inside the blueberry flowers was not significantly different from the conventional dissecting technique, but the time taken to complete the extraction of thrips was significantly shorter. Overall, the highest concentration of thrips was captured inside the canopy of blueberry bushes. Using a grid of traps to monitor the dispersal of thrips during the blueberry flowering season, we analyzed their dispersion with graphical and analytical methods to determine and describe their distribution within blueberry plantings. Thrips began to form "hot-spots" 5-7 d after bloom initiation. A hot-spot is defined as a large number of thrips concentrated in a small area of the field, whereas the rest of the field has a low population. The behavior of the population inside these hot-spots fit a Gaussian tendency and a regression was conducted to describe this tendency. Green's and Standardized Morisita's indices were used to determine thrips level of aggregation. Results showed significantly aggregated populations of thrips in both years. Formation of hot-spots in blueberry plantings seemed to be random. However, the formation of hot-spots was higher in places where more than seven thrips per day were captured on sticky traps, 5 to 7 d after the bloom begins. With these results, producers will be able to monitor thrips populations and locate and manage hot-spots before they become a more serious a problem on blueberry farms.

Biological control of twospotted spider mite, Tetranychus urticae, with predatory mite, Neoseiulus californicus, in strawberries

Greenhouse and field experiments were conducted from 2005 to 2007 to determine the effectiveness of different release times with the predatory mite, Neoseiulus californicus (McGregor), for control of the twospotted spider mite (TSSM), Tetranychus urticae Koch, in strawberries (Fragaria x ananassa Duchesne). The effect of N. californicus releases over time and on development of TSSM populations during a growing season were evaluated. Our hypothesis was that repeated applications of N. californicus, which is currently recommended by biological control companies, might be unnecessary to attain season-long control of TSSM. In greenhouse trials, three treatments consisting of releases of N. californicus at five-day intervals: day 0, day 5, and day 10, and an untreated control were evaluated. The treatment releases significantly reduced TSSM below the control within five days of each release. Neoseiulus californicus significantly reduced TSSM in treatments with high densities (leaflets with > or =40 TSSM) below that of treatments with lower densities (leaflets with < or = 10 TSSM) demonstrating that if released at a predator: prey ratio of 1:10, timing of release does not alter the effectiveness of N. californicus in controlling TSSM. However, we found that if the ratio of predator: prey remains adequate, N. californicus is a more efficient predator at high TSSM densities. Field studies included three treatments consisting of releases of N. californicus at one-month intervals. All treatments significantly reduced TSSM compared with the control plots (no releases). Releases applied early in the season sustained TSSM significantly below those in the control plots for the whole season. Our results indicate that one release of N. californicus is able to sustained control of TSSM in strawberry throughout a growing season if released when TSSM populations are low early in the season in the southeastern United States.

Evaluation of predatory mites and Acramite for control of twospotted spider mites in strawberries in north central Florida

Greenhouse and field experiments were conducted from 2003 to 2005 to determine the effectiveness of two predatory mite species, Phytoseiulus persimilis Athias-Henriot and Neoseiulus californicus (McGregor), and a reduced-risk miticide, Acramite 50 WP (bifenazate), for control of twospotted spider mite, Tetranychus urticae Koch, in strawberries (Fragaria x ananassa Duchesne). In greenhouse tests, three treatments consisting of releases of P. persimilis, N. californicus, and an untreated control were evaluated. Both species of predatory mites significantly reduced twospotted spider mite numbers below those found in the control during the first 3 wk of evaluation. However, during week 4, twospotted spider mite numbers on the plants treated with P. persimilis increased and did not differ significantly from the control. Field studies used releases of P. persimilis and N. californicus, applications of Acramite, and untreated control plots. Both N. californicus and P. persimilis significantly reduced populations of twospotted spider mite below numbers recorded in the control plots. During the 2003-2004 field season P. persimilis took longer than N. californicus to bring the twospotted spider mite population under control (< 10 mites per leaflet). Acramite was effective in reducing twospotted spider mite populations below 10 mites per leaflet during the 2003-2004 field season but not during the 2004-2005 field season, possibly because of a late application. These findings indicate that N. californicus releases and properly timed Acramite applications are promising options for twospotted spider mite control in strawberries for growers in north Florida and other areas of the southeast.

Comparison of single and combination treatments of Phytoseiulus persimilis, Neoseiulus californicus, and Acramite (bifenazate) for control of twospotted spider mites in strawberries

Greenhouse and field experiments were conducted from 2003 to 2005 to determine the effectiveness of combining releases of two predatory mite species, Phytoseiulus persimilis Athias-Henriot and Neoseiulus californicus (McGregor), and a reduced-risk miticide, Acramite (bifenazate), for control of twospotted spider mite (TSSM) (Tetranychus urticae Koch) in strawberries. In the greenhouse experiment, a combination treatment of P. persimilis and N. californicus was compared with single treatments of each species, Acramite application, and untreated control. All treatments significantly reduced TSSM numbers compared with the control. Field studies employed two approaches: one investigating the same five treatments as the greenhouse experiment and a second, comparing combination treatments of P. persimilis/N. californicus, Acramite/N. californicus, and Acramite/P. persimilis to single treatments of each and to control plots. Among the combination treatments, the P. persimilis/N. californicus treatment significantly reduced TSSM numbers compared with the control, but was not as effective as N. californicus alone during the 2003-2004 field season. Also, combination treatments of Acramite/N. californicus, and Acramite/P. persimilis significantly reduced TSSM populations compared with the control. These findings indicate that all three combination treatments are promising options for TSSM control in strawberries for growers in northern Florida and other strawberry producing areas of the world.

Effects of soil moisture and temperature on reproduction and development of twospotted spider mite (Acari: Tetranychidae) in strawberries

The effects of soil moisture and temperature on the reproduction of twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), were examined in laboratory and field tests in strawberries, Fragaria x ananassa Duchesne, in Florida. Different soil moisture levels (low, moderate, and high) were compared to determine how soil moisture affects the reproduction and development of twospotted spider mite. In addition to soil moisture, different irrigation techniques (drip versus drip/overhead) were compared to determine their effects on twospotted spider mite reproduction as well as the incidence of angular leaf spot, Xanthomonas fragaria Kennedy & King disease. Similar studies were conducted to determine how different temperatures (18, 27, and 35 degrees C) affect the reproduction and development of twospotted spider mites. In the laboratory, low soil moisture as well as temperatures >27 degrees C promoted twospotted spider mite development. A similar trend was observed in a field study with low soil moisture promoting twospotted spider mite reproduction during the early season (11 November--8 December). Irrespective of moisture levels, a significantly higher incidence of X. fragaria was recorded in treatments with drip/overhead irrigation systems compared with drip irrigation. Implications for management of soil moisture levels are discussed with respect to the abundance of twospotted spider mite and X. fragaria in strawberries.

Behavioral evidence for host fidelity among populations of the parasitic wasp, Diachasma alloeum (Muesebeck)

The concept of "host fidelity," where host-specific mating occurs in close proximity to the oviposition site and location of larval development, is thought to impart a pre-mating isolation mechanism for sympatric speciation (sensu members of the genus Rhagoletis). The apple maggot fly, Rhagoletis pomonella, and the blueberry maggot fly, R. mendax, are morphologically similar sibling species thought to have speciated in sympatry by divergence of host plant association. Both of these fly species are attacked by the specialist braconid parasitoid, Diachasma alloeum. The current study demonstrates that both male and female D. alloeum exhibit a behavioral preference for the odor of the fruit of their larval Rhagoletis host species. Specifically, those D. alloeum emerging from puparia of R. pomonella are preferentially attracted to hawthorn fruit and those emerging from puparia of R. mendax are preferentially attracted to blueberry fruit. However, male D. alloeum reared from either R. pomonella or R. mendax were equally attracted to females originating from both Rhagoletis species. We suggest that the data herein present evidence for "host fidelity," where populations of D. alloeum exhibit a greater tendency to mate and reproduce among the host plants of their preferred Rhagoletis hosts. Furthermore, host fidelity may have resulted in the evolution of distinct host races of D. alloeum tracking the speciation of their larval Rhagoletis prey.

Toxicity of imidacloprid-treated spheres to Caribbean fruit fly, Anastrepha suspensa (Diptera: Tephritidae) and its parasitoid Diachasmimorpha longicaudata (Hymenoptera: Braconidae) in the laboratory

No-choice cage tests were used to study the toxicity of imidacloprid-treated spheres to Caribbean fruit fly, Anastrepha suspensa (Loew), and its associated parasitoid, Diachasmimorpha longicaudata (Ashmead), in the laboratory. Three imidacloprid sphere treatments (2, 4, and 8% active ingredient [AI] Provado 1.6 F) and an untreated control sphere (no toxicant) were evaluated against A. suspensa. Throughout the observation period (2-72 h), all concentrations of imidacloprid-treated spheres killed significantly more A. suspensa compared with control spheres. After 4 h of exposure to imidacloprid-treated spheres, significantly more A. suspensa were killed on spheres treated with 8% compared with 2% (AI). At 48 and 72 h, there were no significant differences in the mean number of A. suspensa killed at 2, 4, and 8% (AI), potentially indicating that a period of 24 h was sufficient for flies to ingest a lethal dose of the pesticide. Overall, significantly more A. suspensa males were killed after 72 h of exposure to imidacloprid-treated spheres compared with females. For D. longicaudata, only two imidacloprid sphere treatments, 2 and 4% (AI), and an untreated sphere (control) were evaluated for mortality in cage tests. There were no significant differences in mortality of D. longicaudata between the 2 and 4% (AI) imidacloprid-treated spheres. Both rates killed significantly more D. longicaudata compared with the control. However, after 24, 48, and 72 h of exposure to imidacloprid-treated spheres, significantly more D. longicaudata were killed in cages containing 4% compared with 2% (AI) and untreated control spheres. The study demonstrates the potential use of imidacloprid-treated spheres for control of A. suspensa in areas where it may be difficult to apply broad-spectrum insecticides.

Techniques for monitoring cranberry tipworm (Diptera: Cecidomyiidae) in rabbiteye and southern highbush blueberries

Several monitoring techniques were evaluated for their effectiveness, based on the highest mean captures of cranberry tipworm, Dasineura oxycoccana (Johnson), in detecting D. oxycoccana in rabbiteye, Vaccinium ashei Reade, and southern highbush, V. corymbosum L. x V. darrowi Camp, blueberry plantings. There were no significant differences in captures of D. oxycoccana adults on unbaited sticky board traps, regardless of color (yellow, white, green, or blue). In a separate experiment, three monitoring techniques, yellow unbaited sticky boards, larval/adult emergence from infested buds, and bud dissection, were evaluated for detecting D. oxycoccana, eggs, larvae, and adults. In total, four bud types were examined, including rabbiteye floral, rabbiteye leaf, southern highbush floral, and southern highbush leaf. The emergence monitoring technique detected significantly more D. oxycoccana adults than the other techniques evaluated. Emergence and dissection techniques performed equally well for detecting D. oxycoccana larvae. Dissection was the only technique capable of detecting D. oxycoccana eggs. Overall, the highest numbers of D. oxycoccana eggs were detected in southern highbush leaf buds. However, larval infestation was lower for southern highbush leaf buds compared with other bud types sampled. Hypotheses to explain this phenomenon are discussed. The fewest number of eggs was recorded for southern highbush flower buds, potentially because these buds develop before peak emergence of D. oxycoccana. Managing D. oxycoccana in infested plantings can be improved by incorporating monitoring techniques, specifically bud dissection to search for eggs, that will aid growers in making timely insecticide applications.

Comparison of neonicotinoid insecticides for use with biodegradable and wooden spheres for control of key Rhagoletis species (Diptera: Tephritidae)

Field-based studies and laboratory bioassays were conducted with apple maggot, Rhagoletis pomonella (Walsh), and blueberry maggot, Rhgoletis mendax Curran, flies to investigate the performance and duration of activity of insecticide-treated biodegradable and wooden spheres for control of Rhagoletis species. Four neonicotinoid insecticide treatments including imidacloprid, thiamethoxam, and thiocloprid at 2% (AI) were evaluated with biodegradable spheres. In 1999, significantly more apple maggot flies were found killed by imidacloprid-treated spheres compared with thiamethoxam-treated spheres during early and late season. In 2000, spheres treated with either of two formulations of imidacloprid killed significantly more apple maggot flies compared with thiamethoxam, thiocloprid, and untreated spheres. In blueberries, there were no significant differences between the numbers of blueberry maggot flies killed by both imidacloprid-treated or thiamethoxam-treated spheres in 1999. However, during the 2000 blueberry field season, both formulations of imidacloprid were significantly more effective in killing blueberry maggot flies compared with spheres treated with thiamethoxam, thiocloprid and untreated controls. Overall, spheres treated with thiocloprid were ineffective and did not kill significantly more apple maggot or blueberry maggot flies compared with the controls. Laboratory bioassays showed that the effectiveness of field-exposed spheres treated with imidacloprid at 4 and d 8% (AI) and thiamethoxam at 4% (AI) in killing apple maggot flies was not significantly reduced over a 12-wk aging period. Additionally, wooden spheres aged outdoors for 12 wk with and without mold maintained residual activity in laboratory tests, whereas biodegradable spheres of equal aging, with and without mold lost their effectiveness in killing apple maggot flies. In other studies, we confirmed that the addition of an external feeding stimulant (sucrose) significantly increases the effectiveness of both biodegradable and wooden spheres treated with imidacloprid at 2% (AI).

Evaluation of various deployment strategies of imidacloprid-treated spheres in highbush blueberries for control of Rhagoletis mendax (Diptera: Tephritidae)

Biodegradable, ammonium-baited spheres treated with the neonicotinoid insecticide Provado (imidacloprid) at 2% (AI) were evaluated for controlling blueberry maggot flies, Rhagoletis mendax Curran. Three strategies for sphere deployment in highbush blueberries, Vaccinium corymbosum L., were compared with untreated control plots in 1999 and once again compared against control plots and organophosphate insecticide sprays in 2000. The patterns of sphere deployment were as follows: (1) perimeter deployment in which spheres were hung individually and spaced equally around the perimeter of experimental plots; (2) cluster deployment in which four groups of three spheres were hung in equally spaced perimeter locations of experimental plots; and (3) uniform deployment in which spheres were placed 10 m apart (in a grid-like pattern) within experimental plots. In 1999, there were no significant differences in fruit injury levels based on observed R. mendax oviposition scars and reared larvae among plots containing imidacloprid-treated spheres in perimeter, cluster, and internal-grid patterns. However, all plots containing spheres had significantly lower fruit infestation levels (<2%), compared with unsprayed control plots with no spheres deployed, which had infestation levels (>20%). In 2000, there were no significant differences in fruit injury based on observed R. mendax oviposition scars between plots containing imidacloprid-treated spheres in the three deployment strategies tested and plots that received Guthion (Azinphosmethyl) spray applications. However, significantly fewer R. mendax larvae were reared from berries collected from plots that received two applications of Guthion compared with plots in which imidacloprid-treated spheres were deployed. Irrespective of sphere deployment strategies, all sphere-treated and sprayed plots had significantly lower injury levels (<1.5%), based on numbers of reared larvae compared with berries collected from the control plots (>4.0%). Based on captures of flies on unbaited Pherocon AM boards placed in the center of treatment plots, we observed a suppression of R. mendax in plots containing imidacloprid-treated spheres compared with control plots. The potential of using imidacloprid-treated spheres as a behavioral control integrated pest management tactic for blueberry maggot flies is discussed.

Effect of trap size, placement, and age on captures of blueberry maggot flies (Diptera: Tephritidae)

Ammonium acetate and protein hydrolysate baited and unbaited green spheres (3.6, 9.0, and 15.6 cm diameter) were evaluated for effectiveness in capturing blueberry maggot flies, Rhagoletis mendax Curran. Early in the season, baited spheres (9.0 cm diameter) captured significantly more R. mendax flies than spheres of 3.6 and 15.6 cm diameter. As the season progressed, the differences in trap captures became less pronounced among the 3.6-, 9.0-, and 15.6-cm-diameter spheres. In other experiments, the effects of trap positions and age on captures of blueberry maggot flies were assessed. Traps were positioned 15 cm above the bush canopy, 15 cm inside the canopy (from top of the bush), and 45 cm from the ground. Traps placed within the canopy captured 2.5 and 1.5 times as many flies compared with traps placed above the canopy and 45 cm from the ground, respectively. When sticky yellow Pherocon AM boards and green sphere traps were allowed to age in field cages, freshly baited (0 d) yellow sticky boards captured significantly more blueberry maggot flies than boards aged for 11, 28, and 40 d, respectively. No significant differences were observed among boards aged for 11, 28, and 40 d. However, when baited 9-cm sticky spheres were aged in field cages, there were no significant differences between freshly baited spheres and spheres aged for 11 and 28 d, respectively. Spheres aged for 40 d differed significantly from freshly baited ones. The study demonstrated that the baited 9-cm-diameter sphere was more effective in capturing blueberry maggot flies than spheres of 3.6 and 15.6 cm diameter. When this trap is deployed in the center of the bush canopy approximately 15 cm from the top of the bush, it is attractive and accessible to R. mendax flies. The data also indicated that a baited 9-cm sphere has a longer effective life span than Pherocon AM boards when deployed under the same field conditions.