The sublethal effects of pesticides on beneficial arthropods

Assessment of potential sublethal effects of various insecticides on key biological traits of the tobacco whitefly, Bemisia tabaci

The tobacco whitefly Bemisia tabaci is one of the most devastating pests worldwide. Current management of B. tabaci relies upon the frequent applications of insecticides. In addition to direct mortality by typical acute toxicity (lethal effect), insecticides may also impair various key biological traits of the exposed insects through physiological and behavioral sublethal effects. Identifying and characterizing such effects could be crucial for understanding the global effects of insecticides on the pest and therefore for optimizing its management in the crops. We assessed the effects of sublethal and low-lethal concentrations of four widely used insecticides on the fecundity, honeydew excretion and feeding behavior of B. tabaci adults. The probing activity of the whiteflies feeding on treated cotton seedlings was recorded by an Electrical Penetration Graph (EPG). The results showed that imidacloprid and bifenthrin caused a reduction in phloem feeding even at sublethal concentrations. In addition, the honeydew excretions and fecundity levels of adults feeding on leaf discs treated with these concentrations were significantly lower than the untreated ones. While, sublethal concentrations of chlorpyrifos and carbosulfan did not affect feeding behavior, honeydew excretion and fecundity of the whitefly. We demonstrated an antifeedant effect of the imidacloprid and bifenthrin on B. tabaci, whereas behavioral changes in adults feeding on leaves treated with chlorpyrifos and carbosulfan were more likely caused by the direct effects of the insecticides on the insects' nervous system itself. Our results show that aside from the lethal effect, the sublethal concentration of imidacloprid and bifenthrin impairs the phloem feeding, i.e. the most important feeding trait in a plant protection perspective. Indeed, this antifeedant property would give these insecticides potential to control insect pests indirectly. Therefore, the behavioral effects of sublethal concentrations of imidacloprid and bifenthrin may play an important role in the control of whitefly pests by increasing the toxicity persistence in treated crops.

The neonicotinoid insecticide imidacloprid repels pollinating flies and beetles at field-realistic concentrations

Neonicotinoids are widely used systemic insecticides which, when applied to flowering crops, are translocated to the nectar and pollen where they may impact upon pollinators. Given global concerns over pollinator declines, this potential impact has recently received much attention. Field exposure of pollinators to neonicotinoids depends on the concentrations present in flowering crops and the degree to which pollinators choose to feed upon them. Here we describe a simple experiment using paired yellow pan traps with or without insecticide to assess whether the commonly used neonicotinoid imidacloprid repels or attracts flying insects. Both Diptera and Coleoptera exhibited marked avoidance of traps containing imidacloprid at a field-realistic dose of 1 µg L(-1), with Diptera avoiding concentrations as low as 0.01 µg L(-1). This is to our knowledge the first evidence for any biological activity at such low concentrations, which are below the limits of laboratory detection using most commonly available techniques. Catch of spiders in pan traps was also slightly reduced by the highest concentrations of imidacloprid used (1 µg L(-1)), but catch was increased by lower concentrations. It remains to be seen if the repellent effect on insects occurs when neonicotinoids are present in real flowers, but if so then this could have implications for exposure of pollinators to neonicotinoids and for crop pollination.

Insecticidal activity of plant essential oils against the vine mealybug, Planococcus ficus

The vine mealybug, Planococcus ficus (Signoret) (Hemiptera: Pseudococcidae), is a pest in grape vine growing areas worldwide. The essential oils from the following aromatic plants were tested for their insecticidal activity against P. ficus: peppermint, Mentha piperita L. (Lamiales: Lamiaceae), thyme-leaved savory, Satureja thymbra L., lavender, Lavandula angustifolia Mill, and basil, Ocimum basilicum L. Essential oils from peels of the following fruits were also tested: lemon, Citrus limon L. (Sapindales: Rutaceae), and orange, C. sinensis L. The reference product was paraffin oil. Bioassays were conducted in the laboratory by using spray applications on grape leaves bearing clusters of P. ficus of one size class, which mainly represented either 3rd instar nymphs or pre-ovipositing adult females. The LC50 values for each essential oil varied depending on the P. ficus life stage but did not significantly differ between 3(rd) instar nymphs and adult females. The LC50 values of the citrus, peppermint, and thyme-leaved savory essential oils ranged from 2.7 to 8.1 mg/mL, and the LC50 values of lavender and basil oil ranged from 19.8 to 22.5 and 44.1 to 46.8 mg/mL, respectively. The essential oils from citrus, peppermint and thymeleaved savory were more or equally toxic compared to the reference product, whereas the lavender and basil essential oils were less toxic than the paraffin oil. No phytotoxic symptoms were observed on grape leaves treated with the citrus essential oils, and low phytotoxicity was caused by the essential oils of lavender, thyme-leaved savory, and mint, whereas the highest phytotoxicity was observed when basil oil was used.

Lethal and sublethal effects of essential oils from Eucalyptus camaldulensis and Heracleum persicum against the adults of Callosobruchus maculatus

The cowpea weevil, Callosobruchus maculatus F. (Coleoptera: Bruchidae), is an important pest of stored cowpea, Vigna ungiculata (L.) Walpers (Fabales: Fabaceae), with ample distribution in tropical and subtropical regions. Many plant essential oils have a broad-spectrum activity against pest insects, and these oils traditionally have been used in the protection of stored products. In this study, the lethal and sublethal effects of essential oils from Eucalyptus camaldulensis Dehnh. (Myrtales: Myrtaceae) and Heracleum persicum Desf. (Apiales: Apiaceae) were evaluated on the adults of C. maculatus at 26 ± 1° C, 70 ± 5% RH, and a photoperiod of 16:8 L:D. The LC50 values of E. camaldulensis and H. persicum were 56.7 and 219.4 µL/L air after 12 hr and 26.1 and 136.4 µL/L air after 24 hr of exposure, respectively. The LT50 values of E. camaldulensis and H.persicum were 6.3 and 10.9 hr, respectively. The results showed that low lethal concentration (LC20) of essential oils negatively affected the longevity, fecundity, and fertility of female adults. The sex ratio of C. maculatus offspring was not significantly affected by essential oils. Therefore, these essential oils can be suggested for controlling C. maculatus in storage systems. The introduction of essential oils into storage systems could potentially decrease seed losses.

Sublethal contaminant exposure alters behavior in a common insect: important implications for trophic transfer

This study examined the effects of sub-lethal exposure of the ubiquitous pesticide malathion on the behavior of the model orthopteran species, the house cricket (Acheta domesticus). Increasing concentrations of malathion caused male crickets to increase periods of non-directional movement, such as twitching and grooming, directional movement, and to seek out shelter less. These are all behavioral alterations that may increase the cricket's chances of being preyed upon, and thus have the potential for serious ecological consequences through trophic transfer. This study also revealed that female crickets appeared to be less affected by malathion than their male conspecifics, indicating a potential sex-bias in both susceptibility and possible predator attack.

Insecticide toxic effects on Trichogramma ostriniae (Hymenoptera: Trichogrammatidae)

BACKGROUND

The parasitoid Trichogramma ostriniae (Pang and Chen) is a major natural enemy of many lepidopterans, but only a few studies have been conducted on the compatibility of biological and chemical controls. In this study, the selectivity of 30 insecticides to T. ostriniae adults was evaluated.

RESULTS

Among the seven classes of chemicals tested, organophosphates and carbamates had the highest intrinsic toxicity to the wasp, with LC(50) values ranging from 0.032 (0.029-0.038) to 2.38 (1.91-3.15) mg AI L(-1). They are followed by phenylpyrazoles, avermectins, neonicotinoids and pyrethroids, which induce variable toxicity responses, with LC(50) values ranging from 0.14 (0.11-0.21) to 56.67 (48.94-67.24) mg AI L(-1), from 2.57 (1.85-4.28) to 4.48 (3.34-6.83) mg AI L(-1), from 2.48 (1.80-4.03) to 503.6 (457.6-557.5) mg AI L(-1) and from 5.44 (3.95-8.84) to 104.2 (92.48-119.7) mg AI L(-1) respectively. The insect growth regulators (IGRs) exhibited least toxicity to the parasitoid.

CONCLUSION

Risk quotient analysis classifies neonicotinoids, avermectins, pyrethroids, IGRs and phenylpyrazoles (with the exception of butane-fipronil and fipronil) as safe agents to the parasitoid, but categorises organophosphates and carbamates as slightly to moderately toxic or dangerous to T. ostriniae.

The non-target impact of spinosyns on beneficial arthropods

Spinosyn-based products, mostly spinosad, have been widely recommended by extension specialists and agribusiness companies; consequently, they have been used to control various pests in many different cropping systems. Following the worldwide adoption of spinosad-based products for integrated and organic farming, an increasing number of ecotoxicological studies have been published in the past 10 years. These studies are primarily related to the risk assessment of spinosad towards beneficial arthropods. This review takes into account recent data with the aim of (i) highlighting potentially adverse effects of spinosyns on beneficial arthropods (and hence on ecosystem services that they provide in agroecosystems), (ii) clarifying the range of methods used to address spinosyn side effects on biocontrol agents and pollinators in order to provide new insights for the development of more accurate bioassays, (iii) identifying pitfalls when analysing laboratory results to assess field risks and (iv) gaining increasing knowledge on side effects when using spinosad for integrated pest management (IPM) programmes and organic farming. For the first time, a thorough review of possible risks of spinosad and novel spinosyns (such as spinetoram) to beneficial arthropods (notably natural enemies and pollinators) is provided. The acute lethal effect and multiple sublethal effects have been identified in almost all arthropod groups studied. This review will help to optimise the future use of spinosad and new spinosyns in IPM programmes and for organic farming, notably by preventing the possible side effects of spinosyns on beneficial arthropods.

Does transgenic Cry1Ac + CpTI cotton pollen affect hypopharyngeal gland development and midgut proteolytic enzyme activity in the honey bee Apis mellifera L. (Hymenoptera, Apidae)?

The transgenic Cry1Ac (Bt toxin) + CpTI (Cowpea Trypsin Inhibitor) cotton cultivar CCRI41 is increasingly used in China and potential side effects on the honey bee Apis mellifera L. have been documented recently. Two studies have assessed potential lethal and sublethal effects in young bees fed with CCRI41 cotton pollen but no effect was observed on learning capacities, although lower feeding activity in exposed honey bees was noted (antifeedant effect). The present study aimed at providing further insights into potential side effects of CCRI41 cotton on honey bees. Emerging honey bees were exposed to different pollen diets using no-choice feeding protocols (chronic exposure) in controlled laboratory conditions and we aimed at documenting potential mechanisms underneath the CCRI41 antifeedant effect previously reported. Activity of midgut proteolytic enzyme of young adult honey bees fed on CCRI41 cotton pollen were not significantly affected, i.e. previously observed antifeedant effect was not linked to disturbed activity of the proteolytic enzymes in bees' midgut. Hypopharyngeal gland development was assessed by quantifying total extractable proteins from the glands. Results suggested that CCRI41 cotton pollen carries no risk to hypopharyngeal gland development of young adult honey bees. In the two bioassays, honey bees exposed to 1 % soybean trypsin inhibitor were used as positive controls for both midgut proteolytic enzymes and hypopharyngeal gland proteins quantification, and bees exposed to 48 ppb (part per billion) (i.e. 48 ng g(-1)) imidacloprid were used as controls for exposure to a sublethal concentration of toxic product. The results show that the previously reported antifeedant effect of CCRI41 cotton pollen on honey bees is not linked to effects on their midgut proteolytic enzymes or on the development of their hypopharyngeal glands. The results of the study are discussed in the framework of risk assessment of transgenic crops on honey bees.

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.

Combined pesticide exposure severely affects individual- and colony-level traits in bees

Reported widespread declines of wild and managed insect pollinators have serious consequences for global ecosystem services and agricultural production. Bees contribute approximately 80% of insect pollination, so it is important to understand and mitigate the causes of current declines in bee populations . Recent studies have implicated the role of pesticides in these declines, as exposure to these chemicals has been associated with changes in bee behaviour and reductions in colony queen production. However, the key link between changes in individual behaviour and the consequent impact at the colony level has not been shown. Social bee colonies depend on the collective performance of many individual workers. Thus, although field-level pesticide concentrations can have subtle or sublethal effects at the individual level, it is not known whether bee societies can buffer such effects or whether it results in a severe cumulative effect at the colony level. Furthermore, widespread agricultural intensification means that bees are exposed to numerous pesticides when foraging, yet the possible combinatorial effects of pesticide exposure have rarely been investigated. Here we show that chronic exposure of bumblebees to two pesticides (neonicotinoid and pyrethroid) at concentrations that could approximate field-level exposure impairs natural foraging behaviour and increases worker mortality leading to significant reductions in brood development and colony success. We found that worker foraging performance, particularly pollen collecting efficiency, was significantly reduced with observed knock-on effects for forager recruitment, worker losses and overall worker productivity. Moreover, we provide evidence that combinatorial exposure to pesticides increases the propensity of colonies to fail.

Spiders (Araneae) in the pesticide world: an ecotoxicological review

Being one of the most abundant and species-rich groups of natural enemies occurring in all agroecosystems, spiders are variably affected by pesticide applications. Here, a review is given of research on spider ecotoxicology. More than 40 species of spiders and almost 130 pesticides (acaricides, insecticides, fungicides and herbicides) have been tested so far in the field or under laboratory conditions. Field studies show that the degree of population reduction following pesticide application is a function of a number of factors inherent to pesticides, crops and spider species (guilds). These studies also revealed indirect effects via habitat and prey disruption. Among laboratory studies, a number of papers have investigated only the direct lethal effect. A meta-analysis of these data reveals that spiders are mainly affected by acaricides and insecticides, particularly neurotoxic substances. Currently, ecotoxicological research on spiders is focused more on direct sublethal effects on a variety of behavioural traits (locomotion, predation, web-building, reproduction, development) and physiology. Yet a standardised approach to the evaluation of sublethal effects is lacking. A few studies have provided some evidence for hormesis in spiders. Future research should be more concentrated on sublethal effects and the estimation of long-term changes in spider populations as a result of pesticide treatment.

Assessing European egg parasitoids as a mean of controlling the invasive South American tomato pinworm Tuta absoluta

The South American tomato pinworm (Tuta absoluta) has recently invaded Europe and is rapidly spreading in the Afro-Eurasian continent where it is becoming a major pest on tomato crops. Laboratory tests were undertaken to evaluate the potential of 29 European strains of Trichogramma parasitoids to control T. absoluta. In addition to the host itself, the host plant (tomato) was used during the laboratory tests in order to increase the chance of selecting the best parasitoid strains. Trichogramma females were placed with T. absoluta eggs on a tomato leaflet in tubes. We compared the parasitism of T. absoluta by the various Trichogramma species tested to the Trichogramma species currently commercially available for the pest control in Europe, i.e. Trichogramma achaeae. Thereafter, the more promising strains were tested on a larger scale, in mesocosm (i.e. cages in greenhouses) and in greenhouse compartments to evaluate efficiency of laboratory selected strains under cropping conditions. The most efficient strain from the laboratory screening trials did not perform as efficiently under the greenhouse conditions. We discuss differences in parasitism levels among species and strains and among the different scales tested in the experiments, as well as implications of these results for further screening for biocontrol agents.

Combined effects of temperature and pyriproxyfen stress in a full life-cycle test with Chironomus riparius (Insecta)

Traditional risk assessment guidelines employ acute or chronic toxicity tests for a maximum of one generation of organisms. These tests are usually performed in the laboratory at a constant standard temperature, although in the field organisms may experience different temperatures, which may be a source of additional stress. Climate change-related temperature shifts may have serious impacts on ectotherm populations that are key components of the aquatic food chains, particularly in combination with the exposure of pollutants affecting their development. Here, a chronic full life-cycle test with Chironomus riparius from the first-instar larvae in the parental (P) generation until emergence in the subsequent F1 generation was conducted at different temperatures (16 and 24°C), testing the effect of the insect growth regulator pyriproxyfen at 1, 3, 10, 30, and 100 µg/L. The emergence ratios were significantly affected by the interaction of temperature, chemical treatment, and generation, showing that, at lower temperatures, the negative effects of pyriproxyfen exposure were significantly greater in the F1 generation than in the P generation. The development rate showed that the effects of the interactions were significant in the F1 generation, underscoring the importance of extended exposure as a useful amendment to the risk assessment of those agrochemicals potentially influencing developmental and reproductive parameters in intact organisms. Moreover, results demonstrated that any difference from the standard temperature of 20°C might result in additional stress, leading to disruption of biological functions in C. riparius, highlighting the interaction among different global climate change-related variables.

Assessment of physiological sublethal effects of imidacloprid on the mirid bug Apolygus lucorum (Meyer-Dür)

Apolygus lucorum (Meyer-Dür) (Hemiptera: Miridae) is currently one of major mirid pests in the Yangtze River and the Yellow River regions in China. Imidacloprid (neonicotinoid) is widely used against pierce-sucking pest insects, including against A. lucorum. In addition to its direct lethal effect, multiple negative sublethal effects may also occur in exposed insects. We assessed potential sublethal effects of imidacloprid on some biological characteristics of A. lucorum with the aim of increasing rational use of imidacloprid against that cotton pest. The lethal toxicity of imidacloprid on adults of A. lucorum was determined in laboratory conditions by a topical application bioassay (LD(50) = 6.70 ng a.i. [active ingredient]/A. lucorum adult). We also estimated a sublethal dose, LD(5) (0.38 ng a.i./adult), a low lethal dose, LD(25) (1.96 ng a.i./adult), and moderate lethal dose, LD(40) (3.97 ng a.i./adult). The sublethal dose of imidacloprid (LD(5)) shortened the pre-oviposition period of females but increased the time required for eggs to develop (i.e. longer embryogenesis). The low lethal dose (LD(25)) also reduced the pre-oviposition period. Females exposed to the LD(40) laid eggs that developed faster but overall percentage of eggs hatching was reduced. LD(25) and LD(40) reduced longevity of males but not of females. In addition, the susceptibility to seven insecticides generally used on Chinese crops was not modified in A. lucorum previously exposed to the LD(25) of imidacloprid. Our results demonstrate sublethal effects of low doses of imidacloprid on A. lucorum (notably on pre-oviposition period and egg development) which may have an impact on population dynamics of this pest.

Short-term and transgenerational effects of the neonicotinoid nitenpyram on susceptibility to insecticides in two whitefly species

The cosmopolitan silverleaf whitefly, Bemisia tabaci which had coexisted with Trialeurodes vaporariorum in Northern China for many years, has become the dominant species in the last years. Recent reports show that it is gradually displacing the other greenhouse whitefly species. Neonicotinoid, which includes nitenpyram, is a major group of insecticides used against whiteflies in various crops. When exposed to low doses of insecticides, insects may develop resistance by adapting physiologically. The short- and long-term effects of nitenpyram on insecticide sensitivity in B. tabaci biotype B and T. vaporariorum adult populations have been compared in the present study. After being exposed to LC(25) of nitenpyram for 24 h, the B. tabaci biotype B adults showed no significant change in susceptibility to nitenpyram or to five other insecticides: imidacloprid, acetamiprid, abamectin, chlorpyrifos and beta-cypermethrin. By contrast, exposure to the LC(25) of nitenpyram for 24 h led to a significant increase in the susceptibility of T. vaporariorum to nitenpyram and imidacloprid, by 1.8- and 2-fold, respectively. When exposed for seven generations to the LC(25) of nitenpyram, B. tabaci developed 6-fold resistance to nitenpyram, and 3.1- and 5-fold cross-resistance to imidacloprid and acetamiprid, respectively, whereas T. vaporariorum developed lower resistance (3.7-fold) to the nitenpyram and very low cross-resistance to imidacloprid (2.5-fold). The higher adaptable nature of B. tabaci (demonstrated here in the case of nitenpyram) when exposed to low doses of insecticides may provide a selective advantage when competing with T. vaporariorum in crops.

Effects of deltamethrin on the specific discrimination of sex pheromones in two sympatric Trichogramma species

The large amounts of insecticides used for crop protection lead to widespread environmental pollution. Determination of the potential impacts induced by this contamination on key species involved in the equilibrium of ecosystems is therefore a necessity. In this study, we tested the effects of a pyrethroid insecticide, deltamethrin, on the capacity of males from two sympatric Trichogramma species to discriminate the sex pheromones emitted by females of their own species (Trichogramma are parasitoids of Lepidopterous). The impact of an acute exposure as could occur at field edges was evaluated using a dose inducing 20% mortality (LD 20). The impact of a low exposure corresponding to diffuse environmental pollution was evaluated by applying an LD 0.1 (a dose inducing no apparent mortality). For T. semblidis, deltamethrin decreased the specific recognition of sexual pheromones at the higher dose (LD 20) but had no effect on this recognition at the lower dose (LD 0.1). However, deltamethrin decreased the saturation of pheromone receptors at both doses. For T. evanescens, deltamethrin increased the recognition of sexual pheromones at both doses, though not during the same period of observation (at the beginning for the LD 20, at the end for the LD 0.1), but it did not decrease the saturation of the pheromone receptors. These differing results were analyzed considering the behavior of the insects, their level of sensitivity to the insecticide and its mode of action. They provide new insights regarding possible consequences of environmental pollution by insecticides on functional biodiversity.

Phosphine-induced walking response of the lesser grain borer (Rhyzopertha dominica)

BACKGROUND

In spite of the intensive worldwide use of phosphine against stored-product insects, its potential sublethal effects on targeted insect species is seldom recognised and may compromise the efficacy of this fumigant, particularly against phosphine-resistant insects. Therefore, the behavioural response of three populations of the lesser grain borer Rhyzopertha dominica (Coleoptera: Bostrichidae) to sublethal phosphine exposure was assessed.

RESULTS

Concentration-mortality bioassays with phosphine confirmed the resistance status of the insect populations studied, with levels of phosphine resistance of 40.8-fold and 85.7-fold compared with the susceptible population. Regarding walking behaviour, determined using a digital video-tracking system, the phosphine-resistant populations were less active than the susceptible population. In addition, sublethal phosphine exposure decreased the walking activity of all three populations.

CONCLUSION

Phosphine exposure decreased walking activity. Such reduced walking activity is likely to lower the respiration rate, thereby minimising phosphine uptake. As higher phosphine resistance was also associated with reduced walking activity, phosphine-resistant populations may resist phosphine fumigation even more efficiently on account of this behavioural trait, further aiding their physiological resistance, and should be a matter of concern.

Effects of imidacloprid, a neonicotinoid pesticide, on reproduction in worker bumble bees (Bombus terrestris)

Bumble bees are important pollinators whose populations have declined over recent years, raising widespread concern. One conspicuous threat to bumble bees is their unintended exposure to trace residues of systemic neonicotinoid pesticides, such as imidacloprid, which are ingested when bees forage on the nectar and pollen of treated crops. However, the demographic consequences for bumble bees of exposure to dietary neonicotinoids have yet to be fully established. To determine whether environmentally realistic levels of imidacloprid are capable of making a demographic impact on bumble bees, we exposed queenless microcolonies of worker bumble bees, Bombus terrestris, to a range of dosages of dietary imidacloprid between zero and 125 μg L(-1) and examined the effects on ovary development and fecundity. Microcolonies showed a dose-dependent decline in fecundity, with environmentally realistic dosages in the range of 1 μg L(-1) capable of reducing brood production by one third. In contrast, ovary development was unimpaired by dietary imidacloprid except at the highest dosage. Imidacloprid reduced feeding on both syrup and pollen but, after controlling statistically for dosage, microcolonies that consumed more syrup and pollen produced more brood. We therefore speculate that the detrimental effects of imidacloprid on fecundity emerge principally from nutrient limitation imposed by the failure of individuals to feed. Our findings raise concern about the impact of neonicotinoids on wild bumble bee populations. However, we recognize that to fully evaluate impacts on wild colonies it will be necessary to establish the effect of dietary neonicotinoids on the fecundity of bumble bee queens.

Oral toxicity of fipronil insecticide against the stingless bee Melipona scutellaris (Latreille, 1811)

For a better evaluation of the model using Apis mellifera in toxicology studies with insecticides, the oral acute toxicity of the insecticide fipronil against the stingless bee Melipona scutellaris was determined. The results showed that fipronil was highly toxic to M. scutellaris, with a calculated LC(50) (48 h) value of 0.011 ng a.i./μL of sucrose solution and an estimated oral LD(50) (48 h) of 0.6 ng a.i./bee. Our results showed that M. scutellaris bee is more sensitive to fipronil than the model specie A. mellifera.

A nicotinic acetylcholine receptor agonist affects honey bee sucrose responsiveness and decreases waggle dancing

A nicotinic acetylcholine receptor agonist, imidacloprid, impairs memory formation in honey bees and has general effects on foraging. However, little is known about how this agonist affects two specific aspects of foraging: sucrose responsiveness (SR) and waggle dancing (which recruits nestmates). Using lab and field experiments, we tested the effect of sublethal doses of imidacloprid on (1) bee SR with the proboscis extension response assay, and (2) free-flying foragers visiting and dancing for a sucrose feeder. Bees that ingested imidacloprid (0.21 or 2.16 ng bee(-1)) had higher sucrose response thresholds 1 h after treatment. Foragers that ingested imidacloprid also produced significantly fewer waggle dance circuits (10.5- and 4.5-fold fewer for 50% and 30% sucrose solutions, respectively) 24 h after treatment as compared with controls. However, there was no significant effect of imidacloprid on the sucrose concentrations that foragers collected at a feeder 24 h after treatment. Thus, imidacloprid temporarily increased the minimum sucrose concentration that foragers would accept (short time scale, 1 h after treatment) and reduced waggle dancing (longer time scale, 24 h after treatment). The effect of time suggests different neurological effects of imidacloprid resulting from the parent compound and its metabolites. Waggle dancing can significantly increase colony food intake, and thus a sublethal dose (0.21 ng bee(-1), 24 p.p.b.) of this commonly used pesticide may impair colony fitness.

Stress for invasion success? Temperature stress of preceding generations modifies the response to insecticide stress in an invasive pest insect

Adaptation to stressful environments is one important factor influencing species invasion success. Tolerance to one stress may be complicated by exposure to other stressors experienced by the preceding generations. We studied whether parental temperature stress affects tolerance to insecticide in the invasive Colorado potato beetle Leptinotarsa decemlineata. Field-collected pyrethroid-resistant beetles were reared under either stressful (17°C) or favourable (23°C) insecticide-free environments for three generations. Then, larvae were exposed to pyrethroid insecticides in common garden conditions (23°C). Beetles were in general tolerant to stress. The parental temperature stress alone affected beetles positively (increased adult weight) but it impaired their tolerance to insecticide exposure. In contrast, offspring from the favourable temperature regime showed compensatory weight gain in response to insecticide exposure. Our study emphasizes the potential of cross-generational effects modifying species stress tolerance. When resistant pest populations invade benign environments, a re-application of insecticides may enhance their performance via hormetic effects. In turn, opposite effects may arise if parental generations have been exposed to temperature stress. Thus, the outcome of management practices of invasive pest species is difficult to predict unless we also incorporate knowledge of the evolutionary and recent (preceding generations) stress history of the given populations into pest management.

Potential exposure of bees, Apis mellifera L., to particulate matter and pesticides derived from seed dressing during maize sowing

This paper assessed the potential exposure of bees (Apis mellifera L.) to pesticides during maize (Zea mays L.) sowing with pneumatic drills. Data were derived from tests carried out in field tests, comparing two configurations of a pneumatic precision drill: conventional drill; drill with air deflectors. In addition, static tests simulating the sowing under controlled conditions, were performed on the drill equipped with an innovative system developed at CRA-ING. During the field tests, the concentrations in the air of the active ingredients of four insecticides used in maize seed dressing (imidacloprid, clothianidin, thiamethoxam and fipronil) were recorded. The concentrations of active ingredients in the air were used for assessing the quantities of active ingredients that a bee might intercept as it flies in a sort of virtual tunnel, the dimensions of which were dependent upon the bee body cross-section and the length of flight. The results of the field tests show that the air deflectors were not completely effective in reducing the amount of active ingredients dispersed in the air. The results of the static tests with drill equipped with the prototype indicated reductions of the active ingredient air concentrations ranging from 72 % up to 95 %, with reference to the conventional drill. Such ratios were applied to the amounts of active ingredients intercepted by the bees in the virtual tunnel contributing to a consistent reduction of the probability that sub-lethal effects can occur.

Development of biomarkers of exposure to xenobiotics in the honey bee Apis mellifera: application to the systemic insecticide thiamethoxam

This study describes the development of acetylcholinesterase (AChE), carboxylesterases (CaE1, CaE2, CaE3), glutathion-S-transferase (GST), alkaline phosphatase (ALP) and catalase (CAT) as enzyme biomarkers of exposure to xenobiotics such as thiamethoxam in the honey bee Apis mellifera. Extraction efficiency, stability under freezing and biological variability were studied. The extraction procedure achieved good recovery rates in one extraction step and ranged from 65 percent (AChE) to 97.3 percent (GST). Most of the enzymes were stable at -20°C, except ALP that displayed a slight but progressive decrease in its activity. Modifications of enzyme activities were considered after exposure to thiamethoxam at the lethal dose 50 percent (LD(50), 51.16 ng bee(-1)) and two sublethal doses, LD(50)/10 (5.12 ng bee(-1)) and LD(50)/20 (2.56 ng bee(-1)). The biomarker responses revealed that, even at the lowest dose used, exposure to thiamethoxam elicited sublethal effects and modified the activity of CaEs, GST, CAT and ALP. Different patterns of biomarker responses were observed: no response for AChE, an increase for GST and CAT, and differential effects for CaEs isoforms with a decrease in CaE1 and CaE3 and an increase in CaE2. ALP and CaE3 displayed contrasting variations but only at 2.56 ng bee(-1). We consider that this profile of biomarker variation could represent a useful fingerprint to characterise exposure to thiamethoxam in the honey bee A. mellifera. This battery of honey bee biomarkers might be a promising option to biomonitor the health of aerial and terrestrial ecosystems and to generate valuable information on the modes of action of pesticides.

Acute toxicities and sublethal effects of some conventional insecticides on Trichogramma chilonis (Hymenoptera: Trichogrammatidae)

The acute toxicity of 10 conventional insecticides to adult of Trichogramma chilonis Ishii (Hymenoptera: Trichogrammatidae) was bioassayed by membrane method, and then their sublethal effects on the parasitoid were evaluated in the laboratory. Based on sublethal concentration (LC30) values at 8 h after treatment, we determined that adult T. chilonis were the most susceptible to chlorfenapyr, followed by fipronil, spinosad, avermectins, beta-cypermethrin, and cartap, with lethal concentration (LC)30 values of 0.3133, 0.3269, 1.5408, 3.2961, 6.1469, and 9.021 mg/liter, respectively. The field-recommended concentrations of chlorfluazuron, indoxacarb, Bacillus thuringiensis, and tebufenozide caused <30% mortality of treated adults; therefore, they were used to evaluate sublethal effects on the parasitoid. After treatment with sublethal concentration of fipronil and avermectins, the longevity of treated females (1.2 and 1.6 d) was significantly shortened and fecundity (34.7 and 1.6) was remarkably decreased; consequently, the life-table parameters (R0, r(m), lambda, and T) of T. chilonis were statistically lower than those in the control. Cartap and spinosad also reduced longevity (8 and 7.9 d) and fecundity (110.77 and 117.2) of treated adults, but cartap enhanced the female percentage of F1 offspring (61.6%), resulting a statistical higher R0, r(m), and lambda of treated T. chilonis. In contrast, chlorfluazuron and tebufenozide increased longevity (16.4 and 15.4 d) and fecundity (248 and 256.9) of treated adults but slightly decreased the female percentage of F1 offspring (31.4 and 38.1%). Although chlorfenapyr showed no adverse influence on longevity and fecundity, it remarkably reduced the female percentage of F1 offspring (13.5%), leading to a lower R0, r(m), and lambda of treated T. chilonis. Indoxacarb, B. thuringiensis, and beta-cypermethrin had no obvious sublethal effects on the longevity and fecundity of treated adults. Based on these results, we consider B. thuringienesis, chlorfluazuron, indoxacarb, beta-cypermethrin, and tebufenozide safe to T. chilonis, suggesting that these insecticides are compatible with this parasitoid when being used in the field. However, fipronil, chlorfenapyr, spinosad, and avermectins were very harmful to T. chilonis. Timing of application of these insecticides was critical.

Field evaluation of attractive lures for the fruit fly Bactrocera minax (Diptera: Tephritidae) and their potential use in spot sprays in Hubei Province (China)

The Chinese citrus fruit fly, Bactrocera minax (Enderlein) is a univoltine Tephritidae pest that infests Citrus species. Field trials were conducted in 2010 to determine the potential use of a lure based on enzymatical-hydrolyzed beer yeast as liquid bait (hereafter named H-protein bait) for B. minax in the Hubei province, China. In a citrus orchard, we compared the attractiveness among aqueous solutions of H-protein bait, GF-120 fruit fly bait, sugar-vinegar-wine mixture, torula yeast, and Jufeng attractant when used in traps and in spot sprays, that is, lures used in combination with the insecticide trichlorphon. The H-protein bait was the most attractive lure in traps, ensnaring significantly more adults than sugar-vinegar-wine mixture, torula yeast, and Jufeng attractant, in decreasing efficiency order. In spot sprays those with H-protein bait killed significantly more female and male flies within 40 min than those with sugar-vinegar-wine mixture, GF-120, Jufeng attractant, and the control. In addition, the total number of flies killed by H-protein bait during the spot spray duration was higher than other treatments. Our results demonstrated that the H-protein bait may be a useful tool in citrus orchards in China to monitor B. minax populations as well as to manage this pest when used in spot sprays.

Learning impairment in honey bees caused by agricultural spray adjuvants

Background

Spray adjuvants are often applied to crops in conjunction with agricultural pesticides in order to boost the efficacy of the active ingredient(s). The adjuvants themselves are largely assumed to be biologically inert and are therefore subject to minimal scrutiny and toxicological testing by regulatory agencies. Honey bees are exposed to a wide array of pesticides as they conduct normal foraging operations, meaning that they are likely exposed to spray adjuvants as well. It was previously unknown whether these agrochemicals have any deleterious effects on honey bee behavior.

Methodology/Principal Findings

An improved, automated version of the proboscis extension reflex (PER) assay with a high degree of trial-to-trial reproducibility was used to measure the olfactory learning ability of honey bees treated orally with sublethal doses of the most widely used spray adjuvants on almonds in the Central Valley of California. Three different adjuvant classes (nonionic surfactants, crop oil concentrates, and organosilicone surfactants) were investigated in this study. Learning was impaired after ingestion of 20 µg organosilicone surfactant, indicating harmful effects on honey bees caused by agrochemicals previously believed to be innocuous. Organosilicones were more active than the nonionic adjuvants, while the crop oil concentrates were inactive. Ingestion was required for the tested adjuvant to have an effect on learning, as exposure via antennal contact only induced no level of impairment.

Conclusions/Significance

A decrease in percent conditioned response after ingestion of organosilicone surfactants has been demonstrated here for the first time. Olfactory learning is important for foraging honey bees because it allows them to exploit the most productive floral resources in an area at any given time. Impairment of this learning ability may have serious implications for foraging efficiency at the colony level, as well as potentially many social interactions. Organosilicone spray adjuvants may therefore contribute to the ongoing global decline in honey bee health.

Lethal effect of imidacloprid on the coccinellid predator Serangium japonicum and sublethal effects on predator voracity and on functional response to the whitefly Bemisia tabaci

Neonicotinoid insecticides are widely used for controlling sucking pests, and sublethal effects can be expected in beneficial arthropods like natural enemies. Serangium japonicum is an important predator in many agricultural systems in China, and a potential biological control agent against Bemisia tabaci. We evaluated the toxicity of imidacloprid to S. japonicum and its impact on the functional response to B. tabaci eggs. S. japonicum adults exposed through contact to dried residues of imidacloprid at the recommended field rate on cotton against B. tabaci (4 g active ingredient per 100 l, i.e. 40 ppm [part per million]), and reduced rates (25, 20, 15 and 10 ppm) for 24 h showed high mortality rates. The mortality induced by a lowest rate, 5 ppm, was not significantly different than the control group and thus it was considered as a sublethal rate. The lethal rate 50 and hazard quotient (HQ) were estimated to be 11.54 ppm and 3.47 respectively, indicating a risk for S. japonicum in treated fields (HQ > 2). When exposed to dried residues of imidacloprid at the sublethal rate (5 ppm) on cotton leaves, functional response of S. japonicum to B. tabaci eggs was affected with an increase in handling time and a reduction in peak consumption of eggs. Imidacloprid residues also disturbed predator voracity, the number of B. tabaci eggs consumed on treated leaves being significantly lower than on untreated leaves. All effects disappeared within a few hours after transfer to untreated cotton leaves. Imidacloprid systemically applied at the recommended field rate (for cotton) showed no toxicity to S. japonicum, nor affected the functional response of the predator. Sublethal effects of imidacloprid on S. japonicum observed in our study likely negatively affect S. japonicum development and reproductive capacity and may ultimately reduce predator population growth. These results hint at the importance of assessing potential effects of imidacloprid on S. japonicum for developing effective integrated pest management programs of B. tabaci in China.

Effects of Banana Plantation Pesticides on the Immune Response of Lepidopteran Larvae and Their Parasitoid Natural Enemies

Basic research on the insect immune response has progressed dramatically within the last two decades, showing that immunity is one of the most effective defenses against foreign invaders. As such, it is important to understand the causes of variation in this response. Here, we investigate the effects of pesticides used in Costa Rican banana plantations on the immune response of the lepidopteran larva, Caligo memnon (Brassolinae). In addition, we performed a parasitism survey of the banana plantations and surrounding forests to provide a broader assessment of pesticide effects on parasitoid populations. All caterpillars for the immune assay were collected from two banana plantations and brought to La Selva Biology Station for immune challenge. Individuals were fed leaves from the plantations (pesticide) or leaves from La Selva (pesticide-free), then immune challenged with injected sephadex beads. We found that individuals feeding on pesticide leaves had significantly lower bead melanization compared to individuals feeding on pesticide-free leaves. Nonetheless, the parasitism survey showed that caterpillars from the banana plantations had lower parasitism rates compared to caterpillars from the La Selva forest. This study adds to the growing body of evidence documenting negative effects of pesticides on the insect immune response and on adult parasitoids, and underscores the need for more research at the intersection between ecological entomology and immunology.

Imidacloprid-induced impairment of mushroom bodies and behavior of the native stingless bee Melipona quadrifasciata anthidioides

Declines in pollinator colonies represent a worldwide concern. The widespread use of agricultural pesticides is recognized as a potential cause of these declines. Previous studies have examined the effects of neonicotinoid insecticides such as imidacloprid on pollinator colonies, but these investigations have mainly focused on adult honey bees. Native stingless bees (Hymenoptera: Apidae: Meliponinae) are key pollinators in neotropical areas and are threatened with extinction due to deforestation and pesticide use. Few studies have directly investigated the effects of pesticides on these pollinators. Furthermore, the existing impact studies did not address the issue of larval ingestion of contaminated pollen and nectar, which could potentially have dire consequences for the colony. Here, we assessed the effects of imidacloprid ingestion by stingless bee larvae on their survival, development, neuromorphology and adult walking behavior. Increasing doses of imidacloprid were added to the diet provided to individual worker larvae of the stingless bee Melipona quadrifasciata anthidioides throughout their development. Survival rates above 50% were only observed at insecticide doses lower than 0.0056 µg active ingredient (a.i.)/bee. No sublethal effect on body mass or developmental time was observed in the surviving insects, but the pesticide treatment negatively affected the development of mushroom bodies in the brain and impaired the walking behavior of newly emerged adult workers. Therefore, stingless bee larvae are particularly susceptible to imidacloprid, as it caused both high mortality and sublethal effects that impaired brain development and compromised mobility at the young adult stage. These findings demonstrate the lethal effects of imidacloprid on native stingless bees and provide evidence of novel serious sublethal effects that may compromise colony survival. The ecological and economic importance of neotropical stingless bees as pollinators, their susceptibility to insecticides and the vulnerability of their larvae to insecticide exposure emphasize the importance of studying these species.

Dietary traces of neonicotinoid pesticides as a cause of population declines in honey bees: an evaluation by Hill's epidemiological criteria

BACKGROUND

Honey bees are important pollinators of both crops and wild plants. Pesticide regimes that threaten their sustainability should therefore be assessed. As an example, evidence that the agricultural use of neonicotinoid pesticides is a cause of the recently observed declines in honey bees is examined. The aim is to define exacting demographic conditions for a detrimental factor to precipitate a population decline, and Hill's epidemiological 'causality criteria' are employed as a structured process for making an expert judgement about the proposition that trace dietary neonicotinoids in nectar and pollen cause population declines in honey bees.

RESULTS

In spite of the absence of decisive experimental results, the analysis shows that, while the proposition is a substantially justified conjecture in the context of current knowledge, it is also substantially contraindicated by a wide variety of circumstantial epidemiological evidence.

CONCLUSION

It is concluded that dietary neonicotinoids cannot be implicated in honey bee declines, but this position is provisional because important gaps remain in current knowledge. Avenues for further investigations to resolve this longstanding uncertainty are therefore identified.

Using video-tracking to assess sublethal effects of pesticides on honey bees (Apis mellifera L.)

Concern about the role of pesticides in honey bee decline has highlighted the need to examine the effects of sublethal exposure on bee behaviors. The video-tracking system EthoVisionXT (Noldus Information Technologies) was used to measure the effects of sublethal exposure to tau-fluvalinate and imidacloprid on honey bee locomotion, interactions, and time spent near a food source over a 24-h observation period. Bees were either treated topically with 0.3, 1.5, and 3 µg tau-fluvalinate or exposed to 0.05, 0.5, 5.0, 50, and 500 ppb imidacloprid in a sugar agar cube. Tau-fluvalinate caused a significant reduction in distance moved at all dose levels (p < 0.05), as did 50 and 500 ppb imidacloprid (p < 0.001). Bees exposed to 50 and 500 ppb spent significantly more time near the food source than control bees (p < 0.05). Interaction time decreased as time in the food zone increased for both chemicals. This study documents that video-tracking of bee behavior can enhance current protocols for measuring the effects of pesticides on honey bees at sublethal levels. It may provide a means of identifying problematic compounds for further testing.

Response of wild bees (Hymenoptera: Apoidea: Anthophila) to surrounding land cover in Wisconsin pickling cucumber

Cucumber (Cucumis sativus L.) is among the plants highly dependent on insect-mediated pollination, but little is known about its unmanaged pollinators. Both domestic and wild bee populations in central Wisconsin pickling cucumber fields were assessed using a combination of pan trapping and floral observations before and during bloom. Together with land cover analyses extending 2,000 m from field centers, the relationship of land cover components and bee abundance and diversity were examined. Over a 2-yr sample interval distributed among 18 experimental sites, 3,185 wild bees were collected representing >60 species. A positive association was found between both noncrop and herbaceous areas with bee abundance and diversity only during bloom. Response of bee abundance and diversity to land cover was strongest at larger buffers presumably because of the heterogeneous nature of the landscape and connectivity between crop and noncrop areas. These results are consistent with previous research that has found a weak response of wild bees to surrounding vegetation in moderately fragmented areas. A diverse community of wild bees is present within the fields of a commercial cucumber system, and there is evidence of floral visitation by unmanaged bees. This evidence emphasizes the importance of wild pollinators in fragmented landscapes and the need for additional research to investigate the effectiveness of individual species in pollen deposition.

Insect pollinated crops, insect pollinators and US agriculture: trend analysis of aggregate data for the period 1992-2009

In the US, the cultivated area (hectares) and production (tonnes) of crops that require or benefit from insect pollination (directly dependent crops: apples, almonds, blueberries, cucurbits, etc.) increased from 1992, the first year in this study, through 1999 and continued near those levels through 2009; aggregate yield (tonnes/hectare) remained unchanged. The value of directly dependent crops attributed to all insect pollination (2009 USD) decreased from $14.29 billion in 1996, the first year for value data in this study, to $10.69 billion in 2001, but increased thereafter, reaching $15.12 billion by 2009. The values attributed to honey bees and non-Apis pollinators followed similar patterns, reaching $11.68 billion and $3.44 billion, respectively, by 2009. The cultivated area of crops grown from seeds resulting from insect pollination (indirectly dependent crops: legume hays, carrots, onions, etc.) was stable from 1992 through 1999, but has since declined. Production of those crops also declined, albeit not as rapidly as the decline in cultivated area; this asymmetry was due to increases in aggregate yield. The value of indirectly dependent crops attributed to insect pollination declined from $15.45 billion in 1996 to $12.00 billion in 2004, but has since trended upward. The value of indirectly dependent crops attributed to honey bees and non-Apis pollinators, exclusive of alfalfa leafcutter bees, has declined since 1996 to $5.39 billion and $1.15 billion, respectively in 2009. The value of alfalfa hay attributed to alfalfa leafcutter bees ranged between $4.99 and $7.04 billion. Trend analysis demonstrates that US producers have a continued and significant need for insect pollinators and that a diminution in managed or wild pollinator populations could seriously threaten the continued production of insect pollinated crops and crops grown from seeds resulting from insect pollination.

Field assessment of Bt cry1Ah corn pollen on the survival, development and behavior of Apis mellifera ligustica

Honeybees may be exposed to insecticidal proteins from transgenic plants via pollen. An assessment of the impact of such exposures on the honeybee is an essential part of the risk assessment process for transgenic Bacillus thuringiensis corn. A field trial was conducted to evaluate the effect of transgenic Bt cry1Ah corn on the honeybee Apis mellifera ligustica. Colonies of honeybees were moved to Bt or non-Bt corn fields during anthesis and then sampled to record their survival, development and behavior. No differences in immature stages, worker survival, bee body weight, hypopharyngeal gland weight, colony performance, foraging activity or olfactory learning abilities were detected between colonies that were placed in non-Bt corn fields and those placed in Bt corn fields. We conclude that cry1Ah corn carries no risk for the survival, development, colony performance or behavior of the honeybee A. mellifera ligustica.

Imidacloprid affects Pardosa pseudoannulata adults and their unexposed offspring

Imidacloprid is a nicotine-based, systemic, widely used insecticide. In order to investigate the effects of imidacloprid on the spider Pardosa pseudoannulata (Araneae: Lycosidae), specimens were exposed to different concentrations of imidacloprid (12.5, 25, 50, 100, 200 mg/L) by the dipping method. Surviving spiders were used to determine the fecundity, development time of unexposed offspring, predation, and the activities of detoxification enzymes. Significant reductions were observed in survival rate and fecundity of spiders exposed to imidacloprid. The development times of unexposed offspring (F(1)) were prolonged significantly with increased concentrations of imidacloprid. Spiders exposed to concentrations of imidacloprid above 25 mg/L showed significantly weaker predation on Drosophila melanogaster than the control group, but a low dose of imidacloprid (12.5 mg/L) increased predation ability. The activities of carboxyl esterase, acetyl cholinesterase, and the mixed-function oxidase were significantly inhibited by imidacloprid. With increasing concentrations of imidacloprid, the activities of all three kinds of enzymes were decreased significantly. These results suggest that imidacloprid can stimulate the performance of spiders (in low concentration) and has chronic toxicity to the spiders.

Direct effect of acaricides on pathogen loads and gene expression levels in honey bees Apis mellifera

The effect of using acaricides to control varroa mites has long been a concern to the beekeeping industry due to unintended negative impacts on honey bee health. Irregular ontogenesis, suppression of immune defenses, and impairment of normal behavior have been linked to pesticide use. External stressors, including parasites and the pathogens they vector, can confound studies on the effects of pesticides on the metabolism of honey bees. This is the case of Varroa destructor, a mite that negatively affects honey bee health on many levels, from direct parasitism, which diminishes honey bee productivity, to vectoring and/or activating other pathogens, including many viruses. Here we present a gene expression profile comprising genes acting on diverse metabolic levels (detoxification, immunity, and development) in a honey bee population that lacks the influence of varroa mites. We present data for hives treated with five different acaricides; Apiguard (thymol), Apistan (tau-fluvalinate), Checkmite (coumaphos), Miteaway (formic acid) and ApiVar (amitraz). The results indicate that thymol, coumaphos and formic acid are able to alter some metabolic responses. These include detoxification gene expression pathways, components of the immune system responsible for cellular response and the c-Jun amino-terminal kinase (JNK) pathway, and developmental genes. These could potentially interfere with the health of individual honey bees and entire colonies.

Neonicotinoids in bees: a review on concentrations, side-effects and risk assessment

Neonicotinoid insecticides are successfully applied to control pests in a variety of agricultural crops; however, they may not only affect pest insects but also non-target organisms such as pollinators. This review summarizes, for the first time, 15 years of research on the hazards of neonicotinoids to bees including honey bees, bumble bees and solitary bees. The focus of the paper is on three different key aspects determining the risks of neonicotinoid field concentrations for bee populations: (1) the environmental neonicotinoid residue levels in plants, bees and bee products in relation to pesticide application, (2) the reported side-effects with special attention for sublethal effects, and (3) the usefulness for the evaluation of neonicotinoids of an already existing risk assessment scheme for systemic compounds. Although environmental residue levels of neonicotinoids were found to be lower than acute/chronic toxicity levels, there is still a lack of reliable data as most analyses were conducted near the detection limit and for only few crops. Many laboratory studies described lethal and sublethal effects of neonicotinoids on the foraging behavior, and learning and memory abilities of bees, while no effects were observed in field studies at field-realistic dosages. The proposed risk assessment scheme for systemic compounds was shown to be applicable to assess the risk for side-effects of neonicotinoids as it considers the effect on different life stages and different levels of biological organization (organism versus colony). Future research studies should be conducted with field-realistic concentrations, relevant exposure and evaluation durations. Molecular markers may be used to improve risk assessment by a better understanding of the mode of action (interaction with receptors) of neonicotinoids in bees leading to the identification of environmentally safer compounds.

Using organic-certified rather than synthetic pesticides may not be safer for biological control agents: selectivity and side effects of 14 pesticides on the predator Orius laevigatus

The generalist predator Orius laevigatus (Fieber) (Hemiptera: Anthocoridae) is a key natural enemy of various arthropods in agricultural and natural ecosystems. Releases of this predator are frequently carried out, and it is included in the Integrated Pest Management (IPM) programs of several crops. The accurate assessment of the compatibility of various pesticides with predator activity is key for the success of this strategy. We assessed acute and sublethal toxicity of 14 pesticides on O. laevigatus adults under laboratory conditions. Pesticides commonly used in either conventional or organic farming were selected for the study, including six biopesticides, three synthetic insecticides, two sulfur compounds and three adjuvants. To assess the pesticides' residual persistence, the predator was exposed for 3d to pesticide residues on tomato sprouts that had been treated 1 h, 7 d or 14 d prior to the assay. The percentage of mortality and the sublethal effects on predator reproductive capacity were summarized in a reduction coefficient (E(x)) and the pesticides were classified according to the IOBC (International Organization for Biological Control) toxicity categories. The results showed that the pesticides greatly differed in their toxicity, both in terms of lethal and sub lethal effects, as well as in their persistence. In particular, abamectin was the most noxious and persistent, and was classified as harmful up to 14 d after the treatment, causing almost 100% mortality. Spinosad, emamectin, metaflumizone were moderately harmful until 7 d after the treatment, while the other pesticides were slightly harmful or harmless. The results, based on the combination of assessment of acute mortality, predator reproductive capacity pesticides residual and pesticides residual persistence, stress the need of using complementary bioassays (e.g. assessment of lethal and sublethal effects) to carefully select the pesticides to be used in IPM programs and appropriately time the pesticides application (as function of natural enemies present in crops) and potential releases of natural enemies like O. laevigatus.

A Common Pesticide Decreases Foraging Success and Survival in Honey Bees

Neonicotinoid insecticides were introduced in the early 1990s and have become one of the most widely used crop pesticides in the world. These compounds act on the insect central nervous system, and they have been shown to be persistent in the environment and in plant tissues. Recently, there have been controversial connections made between neonicotinoids and pollinator deaths, but the mechanisms underlying these potential deaths have remained unknown. Whitehorn et al. (p. 351 , published online 29 March) exposed developing colonies of bumble bees to low levels of the neonicotinoid imidacloprid and then released them to forage under natural conditions. Treated colonies displayed reduced colony growth and less reproductive success, and they produced significantly fewer queens to found subsequent generations. Henry et al. (p. 348 , published online 29 March) documented the effects of low-dose, nonlethal intoxication of another widely used neonicotinoid, thiamethoxam, on wild foraging honey bees. Radio-frequency identification tags were used to determine navigation success of treated foragers, which suggested that their homing success was much reduced relative to untreated foragers.

Selenium toxicity to honey bee (Apis mellifera L.) pollinators: effects on behaviors and survival

We know very little about how soil-borne pollutants such as selenium (Se) can impact pollinators, even though Se has contaminated soils and plants in areas where insect pollination can be critical to the functioning of both agricultural and natural ecosystems. Se can be biotransferred throughout the food web, but few studies have examined its effects on the insects that feed on Se-accumulating plants, particularly pollinators. In laboratory bioassays, we used proboscis extension reflex (PER) and taste perception to determine if the presence of Se affected the gustatory response of honey bee (Apis mellifera L., Hymenoptera: Apidae) foragers. Antennae and proboscises were stimulated with both organic (selenomethionine) and inorganic (selenate) forms of Se that commonly occur in Se-accumulating plants. Methionine was also tested. Each compound was dissolved in 1 M sucrose at 5 concentrations, with sucrose alone as a control. Antennal stimulation with selenomethionine and methionine reduced PER at higher concentrations. Selenate did not reduce gustatory behaviors. Two hours after being fed the treatments, bees were tested for sucrose response threshold. Bees fed selenate responded less to sucrose stimulation. Mortality was higher in bees chronically dosed with selenate compared with a single dose. Selenomethionine did not increase mortality except at the highest concentration. Methionine did not significantly impact survival. Our study has shown that bees fed selenate were less responsive to sucrose, which may lead to a reduction in incoming floral resources needed to support coworkers and larvae in the field. If honey bees forage on nectar containing Se (particularly selenate), reductions in population numbers may occur due to direct toxicity. Given that honey bees are willing to consume food resources containing Se and may not avoid Se compounds in the plant tissues on which they are foraging, they may suffer similar adverse effects as seen in other insect guilds.

The effect of pymetrozine (Plenum WG-50) on proboscis extension conditioning in honey bees (Apis mellifera: Hybrid var. Buckfast)

Experiments are designed to examine the effects of pymetrozine (Plenum WG-50), a recent systemic pesticide of the pyridine-azomethin family, on Pavlovian conditioning of harnessed foragers. In one set of experiments bees learned a task in which they associated a conditioned stimulus with feeding. A second set of experiments required the bees to learn a discrimination task. Within each experiment, bees received 5 μl of sucrose only, the recommended field dose of Plenum (5 μL of .3 gL(-1), .16 gL(-1) of pymetrozine measured), or 100 times the field dose of Plenum WG 50 thirty minutes prior to training (5 μL of 30 gL(-1), 14 gL(-1) of pymetrozine measured). The Plenum WG 50 was diluted with .88 M sucrose to facilitate the drinking of the pesticide. In addition to varying the concentration, we also investigated the effect of Plenum WG 50 on bees confined to an observation hive and a hive located outside. The results indicated that prior exposure to Plenum WG 50 affected Pavlovian conditioning only when bees were exposed to 100 times the recommended dosage.

A common pesticide decreases foraging success and survival in honey bees

Nonlethal exposure of honey bees to thiamethoxam (neonicotinoid systemic pesticide) causes high mortality due to homing failure at levels that could put a colony at risk of collapse. Simulated exposure events on free-ranging foragers labeled with a radio-frequency identification tag suggest that homing is impaired by thiamethoxam intoxication. These experiments offer new insights into the consequences of common neonicotinoid pesticides used worldwide.

Pest insect olfaction in an insecticide-contaminated environment: info-disruption or hormesis effect

Most animals, including pest insects, live in an “odor world” and depend strongly on chemical stimuli to get information on their biotic and abiotic environment. Although integrated pest management strategies including the use of insect growth regulators (IGRs) are increasingly developed, most insect pest treatments rely on neurotoxic chemicals. These molecules are known to disrupt synaptic transmission, affecting therefore sensory systems. The wide-spread use of neurotoxic insecticides and the growing use of IGRs result in residual accumulation of low concentrations in the environment. These insecticide residues could act as an “info-disruptor” by modifying the chemical communication system, and therefore decrease chances of reproduction in target insects. However, residues can also induce a non-expected hormesis effect by enhancing reproduction abilities. Low insecticide doses might thus induce adaptive processes in the olfactory pathway of target insects, favoring the development of resistance. The effect of sublethal doses of insecticides has mainly been studied in beneficial insects such as honeybees. We review here what is known on the effects of sublethal doses of insecticides on the olfactory system of insect pests.

Insecticides reduce survival and the expression of traits associated with carnivory of carnivorous plants

While agrochemical pollution is thought to be an important conservation threat to carnivorous plants, the effects of insecticides on these taxa have not been quantified previously. Using a combination of lab- and field-based experiments, we tested the effects of commercial and technical grades of three widely used insecticides (carbaryl, lambda-cyhalothrin, and malathion) on survival and the expression of traits associated with carnivory of pink sundews (Drosera capillaris) and Venus flytraps (Dionaea muscipula). Commercial grades were generally more harmful than technical grades under lab and field conditions, but all three insecticides were capable of reducing both survival and the expression of traits associated with carnivory within recommended application rates. However, pink sundews appeared to be more susceptible to insecticides than Venus flytraps, perhaps because of larger numbers of digestive glands on the leaf surfaces. We make several recommendations for future research directions, such as examining the long-term effects of insecticides on carnivorous plant populations, for example in terms of growth rates and fitness. Additionally, future research should include representative species from a wider-range of carnivorous plant growth forms, and explore the mechanism by which insecticides are harming the plants. Given the effects we observed in the present study, we suggest that the use of insecticides should be carefully managed in areas containing vulnerable carnivorous plant species.