Risk assessment of selected insecticides on Tamarixia triozae (Hymenoptera: Eulophidae), a parasitoid of Bactericera cockerelli (Hemiptera: Trizoidae)

Side effects of semi-synthetic insecticide spinetoram on the whitefly parasitoid Encarsia formosa

BACKGROUND

Insecticide risk assessment for biological control agents is essential for implementing integrated pest management (IPM) programs. Spinetoram is a naturally derived insecticide used to control a variety of agricultural sap-sucking insect pests, and Encarsia formosa Gahan (Hymenoptera: Aphelinidae) plays a key role in the biocontrol of greenhouse whiteflies. Despite its presumed safe ecotoxicological profile, the side effects of spinetoram on E. formosa are partially unknown, especially at sublethal doses. In the laboratory, we estimated the lethal concentrations (LC) of spinetoram on E. formosa by topical exposure of pupae and 48 h residual contact exposure of emerged adults. Afterwards, we assessed the impact of spinetoram LCs on the life history traits (juvenile development, adult longevity, parasitism, adult emergence) and population growth parameter (the instantaneous rate of increase, ri) of the parasitoid.

RESULTS

Probit analysis allowed the estimation of LC10 = 0.10 mg/L, LC50 = 0.56 mg/L, and LC90 = 3.28 mg/L. Spinetoram at LC10 had no impact on the observed parameters of E. formosa. Conversely, spinetoram at LC50 and LC90 significantly reduced adult longevity by 19.2% and 40.6%, total parasitism by 33.4% and 38.7%, and total adult emergence by 29.6% and 39.1%, respectively. Also, the ri of E. formosa was significantly affected by spinetoram LC50 and LC90 with a reduction of 8.17 and 29.83%, respectively.

CONCLUSION

Our results suggested that spinetoram significantly threatens the effectiveness of E. formosa when applied at the field recommended rate. However, further validation of spinetoram under greenhouse conditions is required for a comprehensive risk assessment for E. formosa in IPM programs. © 2024 Society of Chemical Industry.

Toxicity assessment of common acaricides and mineral oils on Anagyrus vladimiri, an effective biocontrol agent of citrus mealybug

Chemical pesticides, while playing an important role in the suppression of insect pests, should be used in a manner that minimizes negative effects on natural enemies. The parasitoid, Anagyrus vladimiri Triapitsyn (Hymenoptera: Encyrtidae), plays an important role in the management of mealybug pests of citrus groves in the Mediterranean region. This study was conducted to evaluate the effect of commonly used acaricides (Spirodiclofen, Spirotetramat, Sulfur, Fenpyroximate, Abamectin) and mineral oils (Levanola, EOS, JMS, and Ultrapaz) on acute mortality of A. vladimiri. Toxicity was assessed in 4 cases: (i) direct spray application on adults, (ii) pesticide application on the mummified host, (iii) feeding with contaminated food, and (iv) contact with pesticide residue. The pesticide Abamectin, applied alone and with Levanola oil was highly toxic to adults in all bioassays, with the exception of direct spray application on the mummified host. Fenpyroximate was found to be highly toxic only when sprayed directly on adults, and sulfur was slightly harmful. Mineral oils were harmful when ingested with food; otherwise, they did not cause appreciable adult mortality. The findings of the present study suggest that all tested materials, with the exception of Abamectin and Fenpyroximate, are compatible with the survival of A. vladimiri. Direct ingestion of oils can, however, cause a degree of mortality. Given that indiscriminate use of these pesticides may affect the population ecology of A. vladimiri, they should be used with caution.

Risk assessment of predatory lady beetle Propylea japonica's multi-generational exposure to three non-insecticidal agrochemicals

The effects of non-insecticidal agrochemicals on pest natural predators remain largely unexplored except bees and silkworm. The herbicide quizalofop-p-ethyl (QpE), fungicide thiophanate-methyl (TM), and plant growth regulator mepiquat chloride (MC) have been extensively applied as non-insecticidal agrochemicals. Here, we systematically evaluated multiple effects of these 3 non-insecticidal agrochemicals on three generations of Propylea japonica, an important agroforestry predatory beetle, including the effects on its development, reproduction, enterobacteria, and transcriptomic response. The results showed that QpE exhibited a hormetic effect on P. japonica, thus significantly increasing the survival rate of generation 2 (F2) females, generation 3 (F3) females, and F3 males and body weight of F3 males. However, three successive generations exposed to TM and MC had no significant effect on longevity, body weight, survival rate, pre-oviposition period, and fecundity of P. japonica. Additionally, we investigated the effects of MC, TM, and QpE exposure on gene expression and gut bacterial community of F3 P. japonica. Under MC, TM, and QpE exposure, the overwhelming genes of P. japonica (99.90 %, 99.45 %, and 99.7 %) remained unaffected, respectively. Under TM and MC exposure, differentially expressed genes (DEGs) were not significantly enriched in any KEGG pathway, indicating TM and MC did not significantly affect functions of P. japonica, but under QpE exposure, the expression levels of drug metabolism-related genes were down-regulated. Although QpE treatment did not affect gut dominant bacterial community composition, it significantly increased relative abundances of detoxification metabolism-related bacteria such as Wolbachia, Pseudomonas and Burkholderia in P. japonica. However, TM and MC had no significant effect on the gut bacterial community composition and relative abundance in P. japonica. This study revealed for the first time the mechanism by which P. japonica might compensate for gene downregulation-induced detoxification metabolism decline through altering symbiotic bacteria under QpE exposure. Our findings provide reference for the rational application of non-insecticidal agrochemicals.

Tomato Potato Psyllid Bactericera cockerelli (Hemiptera: Triozidae) in Australia: Incursion, Potential Impact and Opportunities for Biological Control

Incursion and establishment of an exotic pest may threaten natural habitats and disrupt ecosystems. On the other hand, resident natural enemies may play an important role in invasive pest control. Bactericera cockerelli, commonly known as the tomato-potato psyllid, is an exotic pest, first detected on mainland Australia in Perth, Western Australia, in early 2017. B. cockerelli causes direct damage to crops by feeding and indirectly by acting as the vector of the pathogen that causes zebra chip disease in potatoes, although the latter is not present in mainland Australia. At present, Australian growers rely on the frequent use of insecticides to control B. cockerelli, which may lead to a series of negative economic and environmental consequences. The incursion of B. cockerelli also provides a unique opportunity to develop a conservation biological control strategy through strategically targeting existing natural enemy communities. In this review, we consider opportunities to develop biological control strategies for B. cockerelli to alleviate the dependence on synthetic insecticides. We highlight the potential of existing natural enemies to contribute toward regulating populations of B. cockerelli in the field and discuss the challenges ahead to strengthen the key role they can play through conservation biological control.

Effects of tolfenpyrad exposure on development and response mechanism in the silkworm, Bombyx mori

Tolfenpyrad is a broad spectrum of insecticide that can effectively kill different types of pests, including Lepidoptera. However, due to improper use, the adverse effects of tolfenpyrad on beneficial or economic insects have not been well studied. In this study, we systematically investigated the toxic effect of sublethal tolfenpyrad on silkworms. Sublethal tolfenpyrad exposure can affect the body weight, developments days, cocooning rate, eclosion rate and pupation rate. To further study the response mechanism of silkworms to tolfenpyrad stimulation, we compared the different expression genes by transcriptome sequencing and verified them by qRT-PCR. We found that significant changes in the genes expression was involved in xenobiotics biodegradation and metabolism, immune system and digestive system after tolfenpyrad treatment. To further investigate the possible mechanisms by which intestinal microbia in the response to tolfenpyrad, we analysed the microbia changes in the midgut of silkworms by 16S rRNA gene sequencing. The results showed that the relative abundances of Enterobacter and Staphylococcus were increased whereas the Tyzzerella and Methylobacterium-Methylorubrum were decreased after tolfenpyrad stimulation. Taken together, these results indicated that low concentration of tolfenpyrad affect the growth and development of silkworms. Silkworms respond to the toxicity of tolfenpyrad by inducing immune and detoxification-related gene expression or altering microbial composition in the midgut.

Residue and distribution of drip irrigation and spray application of two diamide pesticides in corn and dietary risk assessment for different consumer groups

BACKGROUND

As the use of diamide insecticides on corn continues to increase, there is growing concern about their residue levels on corn and dietary risks to populations. In this study, the distribution, dispersion and transfer efficiency of two diamide insecticides (tetrachlorantraniliprole (TCAP) and cyantraniliprole (CNAP)) in different parts of corn and soil were investigated in a 1-year field trial in Guangzhou and Lanzhou using two different application methods - spray and drip irrigation, respectively - and the dietary risk of the insecticides to different consumer populations was assessed under the two application methods.

RESULTS

The results showed that drip irrigation had a longer persistence period than spraying, and there was a hysteresis in the absorption distribution of the agent in different parts of corn, which was gradually transferred to the leaves after absorption from the roots. The average TE₁ (transfer efficiency) and TE₂ were 0.230-0.261 and 1.749-1.851 for TCAP and 0.168-0.187 and 2.363-2.815 for CNAP, respectively. At corn harvest, both TCAP and CNAP were below detectable levels in soil and corn. For different consumer populations, hazard quotients ranged from 0.001 to 0.066 for TCAP and from 0.003 to 0.568 for CNAP - both well below 100%.

CONCLUSION

This study indicates that TCAP and CNAP applied by spray or drip irrigation are safe for long-term risk of human intake and also provides guidance for the use of both insecticides in agricultural production to control corn pests, especially in arid and semi-arid areas. © 2022 Society of Chemical Industry.

Tomato Varieties Influence the Performance of Tamarixia triozae (Hymenoptera: Eulophidae) on Bactericera cockerelli (Hemiptera: Triozidae) Nymphs

The potato/tomato psyllid Bactericera cockerelli is the Candidatus Liberibacter solanacearum bacterium vector that causes diseases in Solanaceae crops. Pest control is based on synthetic chemical insecticides, plant extracts, and natural enemies such as parasitoids. Tamarixia triozae feeds on nymphs of B. cockerelli, reaching up to 95% parasitism. This work aimed to evaluate the parasitic performance of T. triozae on tomato leaves with B. cockerelli N3 nymphs, using two domesticated (Floradade and Micro-Tom) and one Wild tomato variety. Several assays were completed to identify the parasitoid attraction toward un-infested plants (healthy) and infested plants (damaged) of three varieties. Parasitism preference and "Y" tube olfactometer tests were performed, respectively. The parasitism of Tamarixia triozae showed a preference toward plants of the Floradade variety by 44% compared with the other two varieties (p = 0.0003). T. triozae was more attracted to damaged plants of the Wild variety (p = 0.0523). Healthy plants of Floradade and Micro-Tom varieties attracted a higher proportion of parasitoids, except in the Wild variety, where T. triozae was more attracted to damaged plants. Taken together, the results of this study show that the domestication degree in tomato plants positively influenced the interactions between tomato plants and the parasitoid, T. triozae.

A comprehensive review of zebra chip disease in potato and its management through breeding for resistance/tolerance to 'Candidatus Liberibacter solanacearum' and its insect vector

Zebra chip disease (ZC), associated with the plant pathogenic bacterium 'Candidatus Liberibacter solanacearum' (psyllaurous) (CLso), is a major threat to global potato production. In addition to yield loss, CLso infection causes discoloration in the tubers, rendering them unmarketable. CLso is transmitted by the potato psyllid, Bactericera cockerelli (Šulc) (Hemiptera: Triozidae). ZC is managed by prophylactic insecticide applications to control the vector, which is costly and carries environmental and human health risks. Given the expense, difficulty, and unsustainability of managing vector-borne diseases with insecticides, identifying sources of resistance to CLso and developing varieties that are resistant or tolerant to CLso and/or potato psyllids has become a major goal of breeding efforts. These efforts include field and laboratory evaluations of noncultivated germplasm and cultivars, studies of tubers in cold storage, detailed quantifications of biochemical responses to infection with CLso, possible mechanisms underlying insect resistance, and traditional examination of potato quality following infections. This review provides a brief history of ZC and potato psyllid, a summary of currently available tools to manage ZC, and a comprehensive review of breeding efforts for ZC and potato psyllid management within the greater context of Integrated Pest Management (IPM) strategies. © 2022 Society of Chemical Industry. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Combined thermal and insecticidal stresses on the generalist predator Macrolophus pygmaeus

Ecotoxicological risk assessments of pesticides on non-target arthropods are often carried out under constant and optimal temperature regimes. However, living organisms rarely experience these conditions in real field situations. Understanding the impact of pesticides on non-target beneficial arthropods under temperature stresses is especially important in terms of global warming. We assessed the lethal and sublethal effects of four modern insecticides (chlorantraniliprole, cyantraniliprole, spinetoram, spinosad), on the generalist predator Macrolophus pygmaeus (Hemiptera: Miridae) under a range of temperatures (from 10 to 40°C) frequently experienced in a real field scenario. A reduction coefficient (E_x) was calculated by summarizing the mortality and predator reproductive capacity and, the chemicals were classified according to the International Organization for Biological Control (IOBC) toxicity classes. The insecticides showed a marked synergistic effect with temperature, as the predator mortality and reproductive outputs were significantly correlated with increasing temperatures. Spinosyns interacted significantly with temperature causing the highest mortality and lowest fertility rates. Anthranilic diamides showed a safer ecotoxicological profile compared to spinosyns, with cyantraniliprole being more harmful than chlorantraniliprole. These results suggest that temperature should be taken into account in pesticide ecotoxicology studies within the framework of integrated pest management and the recent climate changes.

Parasitism, host feeding, and transgenerational effects of three insecticides on the eulophid parasitoid Tamarixia triozae when exposed in the immature stages

The ectoparasitoid Tamarixia triozae is a promising biological control agent of the tomato psyllid, Bactericera cockerelli, based on its high parasitism rates on different crops. The parasitism, host feeding, and transgenerational effects (in terms of sex ratio) of T. triozae females exposed to three insecticides (soybean oil, imidacloprid, and abamectin) as eggs, larvae, and pupae were evaluated when a mixture of second, third, fourth, and fifth instars of the host B. cockerelli was offered. The concentrations bioassayed of each insecticide corresponded to the minimum field-registered concentration [MiFRC] and one-half the MiFRC. No parasitism of B. cockerelli second instars was recorded when parasitoid's females were exposed in any of the three immature stages to any of the insecticides. In contrast, in some cases, parasitism of T. triozae females treated as eggs, larvae, or pupae with soybean oil and imidacloprid was reduced in third, fourth, or fifth instar. In most cases, the host feeding was reduced in second and third instar of the host B. cockerelli when T. triozae females were treated as eggs, larvae, or pupae. Any insecticide modified the sex ratio in the F2 generation. In conclusion, both parasitism and host feeding were affected by the insecticides depending on the concentration and on the nymphal instar of the host B. cockerelli offered.

Selectivity of novel and traditional insecticides used for management of whiteflies on the parasitoid Encarsia formosa

BACKGROUND

Encarsia formosa Gahan is the most important parasitoid exploited for the control of whitefly pests of vegetable crops. However, the non-target effects of recently developed insecticides for controlling whiteflies toward this biocontrol agent is little documented. Here we evaluated the susceptibility of E. formosa adults and juveniles to eight commonly used insecticides against whiteflies.

RESULTS

Residual toxicity tests on glass showed that E. formosa adults were susceptible (over 98% mortality after 6 h treated) to field concentrations of the tested neonicotinoids (imidacloprid, acetamiprid, nitenpyram and thiamethoxam), abamectin, cyantraniliprole, and sulfoxaflor at their field concentrations. Pyriproxyfen was harmless to both adult and pupae of E. formosa. A risk quotient analysis showed that toxicity of pyriproxyfen to E. formosa adults was the lowest, followed by acetamiprid and cyantraniliprole. In the leaf residues test, mortality of E. formosa adults under all insecticides decreased when the residue age increased. Interestingly, E. formosa experiencing contact with the residues of most insecticides, except pyriproxyfen and abamectin, parasitized significantly more hosts 5-days after treatment, suggesting a hormetic effect on parasitism.

CONCLUSION

The risk assessment of insecticides indicated that pyriproxyfen and cyantraniliprole were the least toxic to E. formosa. Our results suggest that the inclusion of the insecticides in sustainable integrated pest management programs of whiteflies should be carefully evaluated on a case-by-case basis. © 2019 Society of Chemical Industry.

Lethal effects of selected novel pesticides on immature stages of Trichogramma pretiosum (Hymenoptera: Trichogrammatidae)

BACKGROUND

Trichogramma pretiosum Riley is an important egg parasitoid and biological control agent of caterpillar pests. We studied the acute toxicity of 20 pesticides (14 insecticides/miticides, three fungicides and three herbicides) exposed to recommended field rates. Egg, larval, and pupal stages of the parasitoid in their hosts were dipped in formulated solutions of the pesticides and evaluated 10 days later for percentage of host eggs with holes, number of parasitoids emerged per egg with holes, and stage-specific mortality of immature as well as adult wasps within the host eggs.

RESULTS

Seven insecticides (buprofezin, chlorantraniliprole, spirotetramat, flonicamid, flubendiamide) and miticides (spiromesifen, cyflumetofen), one herbicide (nicosulfuron), and three fungicides (myclobutanil, pyraclostrobin, trifloxystrobin + tebuconazole) caused no significant mortality to immature stages or pre-emergent adult parasitoids relative to controls. By contrast, seven insecticides/miticides (abamectin, acetamiprid, dinotefuran, fipronil, novaluron, spinetoram, tolfenpyrad) adversely affected immature and pre-emergent adult T. pretiosum, with tolfenpyrad being particularly lethal. Two herbicides had moderate (glufosinate ammonium) to severe (s-metolachlor) acute lethal effects on the immature parasitoids.

CONCLUSIONS

This study corroborates earlier findings with adult T. pretiosum. Over half of the pesticides - and all the fungicides - tested in the current study would appear to be compatible with the use of T. pretiosum in integrated pest management programs, with respect to acute parasitoid mortality. © 2017 Society of Chemical Industry.

Side effects of spirotetramat on pupae and adults of a Neotropical strain of Eretmocerus mundus (Hymenoptera: Aphelinidae): Effects on the life parameters and demography

The negative impact of conventional pesticides on the environment is already extensively discussed worldwide. Although the use of chemical agents for controlling agricultural pests remains as first-line strategy for pest control, novel biorational active insecticides, such as spirotetramat, have appeared in the pesticide market during recent years in Argentina. The aim of this study was to assess the toxicity of spirotetramat on two developmental stages of a Neotropical strain of Eretmocerus mundus, with the conventional insecticide cypermethrin as a positive control, and to determine spirotetramat's side effects on parasitoid demographic parameters. Lethal effects of both insecticides on pupae and adults were evaluated by adult emergency and survival, respectively; whereas sublethal effects on both development stages were assessed by adult longevity, reproduction capacity, sex ratio, and longevity of the first progeny. Spirotetramat proved less harmful than cypermethrin at both developmental stages studied, corroborating once more the high toxicity of this pyrethroid to natural enemies. Although spirotetramat did not affect the emergence and reproductive capacity of adults surviving pupal exposure, the longevity of the first progeny was reduced as was adult survival and longevity after exposure to residues. Spirotetramat also reduced all demographic parameters in the population evaluation. This work is the first report of spirotetramat toxicity at the population level and demonstrates the need to assess the total effect of pesticides on natural enemies.

Lethal and behavioral effects of selected novel pesticides on adults of Trichogramma pretiosum (Hymenoptera: Trichogrammatidae)

BACKGROUND

Growing demand for reduced chemical inputs in agricultural systems requires more effective integration of biological control with pesticides. The egg parasitoid Trichogramma pretiosum Riley is an important natural enemy of lepidopteran pests, used in biological control. In an investigation of the interaction of T. pretiosum and pesticides, we studied the acute toxicity of 19 pesticides (insecticides, miticides, fungicides and herbicides) to adult parasitoids and the behavioral effects of 11 pesticides on foraging parasitoid females, including host antennation, stinging and host feeding.

RESULTS

At recommended field doses, fipronil, dinotefuran, spinetoram, tolfenpyrad and abamectin induced nearly 100% adult mortality within 24 h of exposure to treated cotton leaves by comparison with controls. Acetamiprid was also toxic, but significantly less so than the former materials. The other pesticides had no significant toxic effects. Only glufosinate ammonium exhibited increased toxicity among the non-toxic materials when increased two- or fourfold over recommended rates. The foraging behavior of parasitoids was affected only by tolfenpyrad among the materials tested.

CONCLUSION

Most novel pesticides, except for several insecticides, exhibited little to no acute toxicity to the parasitoid. Parasitoid foraging behavior was only affected by tolfenpyrad, indicating that parasitoids could successfully forage on eggs treated with most pesticides evaluated. Therefore, many of these pesticides may have good compatibility with Trichogramma.

Toxicity and Residual Activity of Insecticides Against Tamarixia triozae (Hymenoptera: Eulophidae), a Parasitoid of Bactericera cockerelli (Hemiptera: Triozidae)

Bactericera cockerelli (Sulc) (Hemiptera: Triozidae) is one of the most economically important pests of potato, tomato, and peppers in Central America, Mexico, the United States, and New Zealand. Its control is based on the use of insecticides; however, recently, the potential of the eulophid parasitoid Tamarixia triozae (Burks) (Hymenoptera: Eulophidae) for population regulation has been studied. Because T. triozae is likely to be exposed to insecticides on crops, the objective of this study was to explore the compatibility of eight insecticides with this parasitoid. The toxicity and residual activity (persistence) of spirotetramat, spiromesifen, beta-cyfluthrin, pymetrozine, azadirachtin, imidacloprid, abamectin, and spinosad against T. triozae adults were assessed using a method based on the residual contact activity of each insecticide on tomato leaf discs collected from treated plants growing under greenhouse conditions. All eight insecticides were toxic to T. triozae. Following the classification of the International Organization of Biological Control, the most toxic were abamectin and spinosad, which could be placed in toxicity categories 3 and 4, respectively. The least toxic were azadirachtin, pymetrozine, spirotetramat, spiromesifen, imidacloprid, and beta-cyfluthrin, which could be placed in toxicity category 2. In terms of persistence, by day 5, 6, 9, 11, 13, 24, and 41 after application, spirotetramat, azadirachtin, spiromesifen, pymetrozine, imidacloprid, beta-cyfluthrin, abamectin, and spinosad could be considered harmless, that is, placed in toxicity category 1 (<25% mortality of adults). The toxicity and residual activity of some of these insecticides allow them to be considered within integrated pest management programs that include T. triozae.

Lethal and Sublethal Impacts of Acaricides on Tamarixia radiata (Hemiptera: Eulophidae), an Important Ectoparasitoid of Diaphorina citri (Hemiptera: Liviidae)

The use of synthetic acaricides for management of pest mites may alter the efficacy of the ectoparasitoid Tamarixia radiata (Waterston) in biological control of Diaphorina citri Kuwayama, the vector of the bacteria associated with huanglongbing (HLB) in citrus orchards. We evaluated the toxicity of 16 acaricides that are recommended for the control of citrus-pest mites to T. radiata. Acrinathrin, bifenthrin, carbosulfan, and fenpropathrin caused high acute toxicity and were considered harmful (mortality >77%) to T. radiata. Abamectin, diflubenzuron, etoxazole, fenbutatin oxide, fenpyroximate, flufenoxuron, hexythiazox, propargite, spirodiclofen, and sulfur caused low acute toxicity and affected the parasitism rate and emergence rate of adults (F1 generation), and were considered slightly harmful to T. radiata. Dicofol and pyridaben did not affect the survival and action of the ectoparasitoid, and were considered harmless. In addition to its acute toxicity, carbosulfan caused mortality higher than 25% for >30 d after application, and was considered persistent. Acrinathrin, bifenthrin, fenpropathrin, fenpyroximate, propargite, and sulfur caused mortalities over 25% until 24 d after application and were considered moderately persistent; abamectin was slightly persistent, and fenbutatin oxide was short lived. Our results suggest that most acaricides used to control pest mites in citrus affect the density and efficacy of T. radiata in the biological control of D. citri. However, further evaluations are needed in order to determine the effect of these products on this ectoparasitoid under field conditions.

Are Mummies and Adults of Eretmocerus mundus (Hymenoptera: Aphelinidae) Compatible With Modern Insecticides?

The parasitic wasp Eretmocerus mundus (Mercet) is an important natural enemy of the widespread key pest Bemisia tabaci (Gennadius). The toxicity of 11 modern insecticides applied at their maximum field recommended rate in Spain was tested in two life stages of E. mundus: adults and mummies. Laboratory and persistence tests were conducted and effects assessed not only in terms of mortality but on reproductive performance as well. Some insecticides caused the same effect to both life stages: flubendiamide, methoxyfenozide, spiromesifen, and flonicamid were harmless, while spinosad and sulfoxaflor were harmful. The last two insecticides cannot be used jointly with E. mundus under any condition because they were highly persistent. The rest of tested insecticides (spirotetramat, metaflumizone, deltamethrin, abamectin, and emamectin) caused some direct mortality to one or both life stages and/or affected reproduction of the parasitic wasp and their harmful effect in the field ranged from short lived (metaflumizone and spirotetramat) to slightly persistent (emamectin) and to moderately persistent (abamectin and deltamethrin). Therefore, they could be recommended for use in integrated pest management programs together with the natural enemy if appropriate safety intervals after insecticide application are observed.

Combined Non-Target Effects of Insecticide and High Temperature on the Parasitoid Bracon nigricans

We studied the acute toxicity and the sublethal effects, on reproduction and host-killing activity, of four widely used insecticides on the generalist parasitoid Bracon nigricans (Hymenoptera: Braconidae), a natural enemy of the invasive tomato pest, Tuta absoluta (Lepidoptera: Gelechiidae). Laboratory bioassays were conducted applying maximum insecticide label rates at three constant temperatures, 25, 35 and 40°C, considered as regular, high and very high, respectively. Data on female survival and offspring production were used to calculate population growth indexes as a measure of population recovery after pesticide exposure. Spinetoram caused 80% mortality at 25°C and 100% at higher temperatures, while spinosad caused 100% mortality under all temperature regimes. Cyantraniliprole was slightly toxic to B. nigricans adults in terms of acute toxicity at the three temperatures, while it did not cause any sublethal effects in egg-laying and host-killing activities. The interaction between the two tested factors (insecticide and temperature) significantly influenced the number of eggs laid by the parasitoid, which was the lowest in the case of females exposed to chlorantraniliprole at 35°C. Furthermore, significantly lower B. nigricans demographic growth indexes were estimated for all the insecticides under all temperature conditions, with the exception of chlorantraniliprole at 25°C. Our findings highlight an interaction between high temperatures and insecticide exposure, which suggests a need for including natural stressors, such as temperature, in pesticide risk assessments procedures.

Behavior of Tamarixia triozae Females (Hymenoptera: Eulophidae) Attacking Bactericera cockerelli (Hemiptera: Triozidae) and Effects of Three Pesticides on This Parasitoid

The parasitism and host feeding behavior of Tamarixia triozae (Burks) (Hymenoptera: Eulophidae) females on Bactericera cockerelli (Sulc) (Hemiptera: Triozidae) fourth instars that have infested tomato (Lycopersicon esculentum Miller) leaflets are described and quantified. Females took approximately 31.14 ± 4.39 min to search for their first suitable host. The recognition and handling times for oviposition were 2.66 ± 0.18 and 4.26 ± 0.39 min, respectively. T. triozae parasitized 4.66 ± 0.61 nymphs in a period of 6 h. The parasitoid explored and probed its host by walking along the margins of its body while antennating and repeatedly introducing the ovipositor beneath the nymph. The handling times before and during host feeding were 8.42 ± 0.67 and 8.29 ± 0.60 min, respectively. T. triozae females consumed 1.00 ± 0.00 B. cockerelli nymph after parasitizing 3.3 ± 0.48 nymphs. EPA-a refined soybean oil-imidacloprid, and abamectin caused between ~70 and 100% T. triozae adult mortality after a 48-h contact treatment with fresh pesticide residue and a 47-91% decrease (abamectin > imidacloprid > EPA) in adult emergence when parasitized B. cockerelli fourth instars were directly sprayed. These data suggest that the use of these insecticides in combination with T. triozae in integrated pest management programs should be carefully evaluated.

Effects of cyantraniliprole, a novel anthranilic diamide insecticide, against Asian citrus psyllid under laboratory and field conditions

BACKGROUND

The Asian citrus psyllid, Diaphorina citri (Hemiptera: Psyllidae), is the most destructive pest of citrus in Florida. The development of insecticide resistance in several populations of D. citri has been documented. There is an urgent need to develop and integrate novel tools for the successful management of D. citri and also to prevent the development of insecticide resistance.

RESULTS

The effects of a relatively newer chemistry, cyantraniliprole, against D. citri were investigated. The contact toxicity of cyantraniliprole was 297-fold higher against D. citri than its primary parasitoid, Tamarixia radiata (Hymenoptera: Eulophidae). D. citri settled and fed less on cyantraniliprole-treated plants than controls at concentrations as low as 0.025 and 0.125 µg AI mL⁻¹ respectively. D. citri egg production, first-instar emergence and adult emergence were significantly reduced on plants treated with 0.25, 0.02 and 0.25 µg AI mL⁻¹ of cyantraniliprole, respectively, when compared with control plants. Under field conditions, foliar and drench treatments with cyantraniliprole (1436.08 g ha⁻¹) reduced numbers of D. citri adults and nymphs, as well as of a secondary pest, citrus leafminer, Phyllocnistis citrella (Lepidoptera: Gracillariidae), more than a standard insecticide.

CONCLUSIONS

These results suggest that cyantraniliprole should be a valuable new tool for rotation into D. citri management programs. For insecticide resistance management, cyantraniliprole may be particularly useful for rotation with neonicotinoids. In addition, cyantraniliprole was much less toxic to T. radiata than to D. citri and thus may have less impact on biological control than other currently used broad-spectrum insecticides, such as organophosphates and pyrethroids.

Side effects of two reduced-risk insecticides, indoxacarb and spinosad, on two species of Trichogramma (Hymenoptera: Trichogrammatidae) on cabbage

Trichogramma pretiosum Riley and T. brassicae Bezdenko are common egg parasitoids of many lepidopteran pest species damaging vegetable, but their effectiveness can be severely curtailed by insecticide applications. To identify insecticides that are potentially compatible with these parasitoid species, the effects of indoxacarb and spinosad were bioassayed in the laboratory. The bioassays included exposure of adults to various aged residues on glass and cabbage leaf surfaces at different intervals after application, and direct spray on host eggs for effects on parasitism and development and mortality of parasitoid eggs, young and old larvae and pupae. The results showed that the glass- and leaf-surface residues of indoxacarb were harmless to both parasitoid species, whereas those of spinosad were moderately harmful to harmful to both parasitoid species depending on the rates used. The use of indoxacarb on host eggs did not affect significantly parasitism by both parasitoid species, whereas the higher rates of spinosad reduced parasitism. However, both insecticides did not affect immature development and adult emergence. Results from direct spray of host eggs with various immature stages inside showed that indoxacarb did not have significant effects on the egg, young and old larval stages and the pupal stage; whereas the high rates of spinosad when applied at the older larval and pupal stages significantly reduced adult emergence for both parasitoid species. Therefore, application of spinosad in an agro-ecosystem where Trichogramma are dominant should be carefully evaluated or avoided.