Field-recommended Concentrations Research Articles

Azoxystrobin Exposure Impacts on Development Status and Physiological Responses of Worker Bees (Apis mellifera L.) from Larval to Pupal Stages

Honeybee larvae and pupae form the cornerstone of colony survival, development, and reproduction. Azoxystrobin is an effective strobilurin fungicide that is applied during the flowering stage for controlling plant pathogens. The contaminated nectar and pollen resulting from its application are collected by forager bees and impact the health of honeybee larvae and pupae. The current study evaluated the survival, development, and physiological effects of azoxystrobin exposure on the larvae and pupae of Apis mellifera worker bees. The field-recommended concentrations of azoxystrobin were found to suppress the survival indices and lifespan in the larval as well as pupal stages; moreover, the rates of the survival and pupation of larvae as well as the body weights of the pupae and newly-emerged adult bees were significantly reduced upon long-term exposure to azoxystrobin. In addition, azoxystrobin ingestion induced changes in the expression of genes critical for the development, immunity, and nutrient metabolism of larvae and pupae, although the expression profile of these genes differed between the larval and pupal stages. Results indicated the chronic toxicity of azoxystrobin on the growth and development of honeybee larvae and pupae, which would affect their sensitivity to pathogens and other external stresses during the development stage and the study will provide vital information regarding the pollination safety and rational use of pesticides.

Learning, memory, and sensory perception are impaired by exposure to the organophosphate, ethion, and the insect growth regulator, hexaflumuron, in honey bees (Apis mellifera L.)

Insecticides are a major tool for controlling pest species. Their widespread use results in damage to non-targeted insects, with honey bees particularly at risk. During foraging, honey bees learn and remember floral characteristics that are associated with food. As insect pollinators, honey bees inadvertently contact chemicals which can have multiple negative impacts. The toxicity of two insecticides from different classes, ethion (47.79 mg a.i.L−1) and hexaflumuron (500 mg a.i.L−1), on learning, memory, and sensory perception were evaluated. We found that oral exposure to ethion had adverse effects on learned proboscis extension toward reward-associated odors and colors. In addition, we showed reduced sucrose consumption and sucrose responsiveness after exposure. Hexaflumuron also impaired olfactory learning and memory and decreased responsiveness to sucrose and water. Exposure to sub-lethal concentration of the cholinergic organophosphate insecticide, ethion (47.79 mg a.i.L−1), and the field-recommended concentration of hexaflumuron (500 mg a.i.L−1), significantly impaired behavior involved in foraging. Our results suggest that several behavioral characteristics of honey bees be evaluated when testing an insecticide rather than relying on just one behavioral measure.

The Comparison of Tolerance Capability of Nitrogen-Fixing Bacteria to Chemical and Biological Pesticides

Due to concerns about the adverse effects of synthetic pesticides on the environment and human health, there is a growing preference for environmentally friendly and safe pesticides. However, hard evidence to verify their low-risk characteristics is scarce. This work attempted to compare the effects of a chemical pesticide (alpha-cypermethrin) and a biopesticide (emamectin benzoate) on the growth of indigenous nitrogen-fixing bacteria. These bacterial strains were isolated from the rhizosphere of bean plant samples obtained from farmers? fields where these two pesticides were sprayed on bean crops. The results revealed that at the field-recommended concentration of both pesticides, the growth of the isolates in both nutrient-rich and nitrogen-free media remained largely unaffected. However, the bacteria?s absolute growth inhibition was recorded as the pesticide concentration increased. When the Tryptic Soy Broth medium was supplemented with a pesticide concentration 10 times higher than the recommended dose, up to 85.7% of the isolated strains were completely inhibited in growth when exposed to alpha-cypermethrin. In contrast, only 17.9% of bacterial strains were completely inhibited when exposed to emamectin benzoate. In a nitrogen-free medium, the proportion of inhibited bacteria was absolute when the medium was supplemented with alpha-cypermethrin and emamectin benzoate at a dosage 10 times higher than the recommended concentration, which reached 92.9% and 28.6%, respectively. The strains that exhibited higher tolerance to both pesticides were identified as Niallia nealsonii ND15 and Rhizobium subbaraonis ND27. Our findings emphasize the importance of minimizing pesticide accumulation in the soil to protect the viability of soil-beneficial bacteria and ensure soil quality for safe and sustainable crop production.. KEYWORDS :Alpha-cypermethrin, Emamectin benzoate, N-fixing bacteria, Pesticides tolerance, Toxicity assessment

Low concentrations of acetamiprid, deltamethrin, and sulfoxaflor, three commonly used insecticides, adversely affect ant queen survival and egg laying

Ants are key ecosystem service providers and can serve as important biological control agents in pest management. However, the effects of insecticides on common farmland ant species are poorly understood. We tested the effects of three commonly used insecticides on ants (Hymenoptera, Formicidae). The tested insecticides were acetamiprid (neonicotinoid; formulated as Mospilan 20 SP), deltamethrin (pyrethroid; formulated as Sanium Ultra), and sulfoxaflor (sulfilimine; formulated as Gondola). We tested two ant (Hymenoptera: Formicidae) species with different colony founding strategies, Lasius niger (Linnaeus, 1758) and Myrmica rubra (Linnaeus, 1758). We sprayed their queens with insecticides at concentrations recommended for use in foliar applications in agriculture, i.e., at 1.25 g L−1 (acetamiprid), 0.6 g L−1 (sulfoxaflor), and 0.875 g L−1 (deltamethrin). Further, we diluted the compounds in distilled water and tested them at 10%, 1%, and 0.1% of the field-recommended concentrations, and used distilled water as a control. We monitored the survival of the queens and the number of eggs laid. All three tested insecticides caused severe lethal and sublethal concentration-dependent effects. Even at concentrations three orders of magnitudes lower than recommended for field applications, significantly lower numbers of eggs were found in the queens’ nests. The extent of the sublethal effects of acetamiprid and sulfoxaflor was concentration-dependent and differed between the two ant species. Besides bees and bumblebees, ants represent an important group of hymenopterans that are severely affected even by low concentrations of the tested compounds and therefore should be included in risk assessment schemes.

Effects of fungicides propiconazole and Trichoderma spp. on the mortality and the physiological status of larvae and adult worker honey bees (Apis mellifera L.)

Exposure to pesticides may affect the survival and normal physiological functions of the honey bee (Apis mellifera L.). The fungicide propiconazole (PRO) and the biofungicide Trichoderma are widely used in agroecosystems, and their effects on the physiology of the honey bee have been largely neglected in risk assessment procedures. We investigated the mortality and variations in physiological biomarkers of honey bee larvae and newly emerged workers exposed to PRO and Trichoderma. Exceeding the field-recommended concentrations of Trichoderma decreased the survival of newly emerged bee workers significantly through oral exposure. PRO, however, showed no significant lethal effects. Contact or oral exposure to field-realistic concentrations of PRO and Trichoderma profoundly altered the activities of detoxification, antioxidative, and digestive enzymes along with energy reserve concentrations of honey bee larvae and adult workers. Integrated biological index (IBRv2) values suggested potential risks of PRO and Trichoderma to honey bees by impairing the physiological status of larvae and newly emerged workers.

Evaluation of Persistent Toxicity of Insecticides against Spodoptera litura on Sunflower at Elevated CO2 and Temperature Conditions

Insecticides with different mode of actions viz., spinosad, emamectin benzoate, thiodicarb, monocrotophos and fenvalerate were applied at LC50 and field recommended concentrations (FRC) to study the persistence of insecticides under elevated CO2 (550 ± 25 ppm) and temperatures (28, 29, 31, 33 and 35ºC). These insecticides often caused significantly higher mortalities at 28ºC than at 35ºC. The mean per cent corrected mortality, persistence in days and persistent toxicity values decreased for all insecticides with increase in temperatures at both levels of CO2 and corresponding temperatures. Among the five insecticides, emamectin benzoate (13 days) and spinosad (12 days) persisted for longer periods with highest mean per cent corrected mortality (58.1 and 56.3) with PT values of 749.5 and 675.0, respectively. The next in order were thiodicarb, monocrotophos and fenvalerate.

Sublethal effects enhance detrimental impact of insecticides on non-target organisms: A quantitative synthesis in parasitoids

Parasitoids acting as biocontrol agents provide farmers with valuable ecosystem services, but are sensitive to insecticides applied against pests. Besides lethal effects of insecticides, sublethal effects observed among survivors may further influence parasitoids’ performance. However, information on sublethal effects is scattered across case studies, without a quantitative synthesis and evaluation of generality of respective data. We conducted an analysis of 85 primary empirical datasets to quantify sublethal effects of insecticide application on two key parameters of parasitoid fitness, offspring production and proportion of females among offspring (i.e. sex ratio). To create a direct link to existing agricultural practices, we primarily focused on studies in which parasitoids were exposed to field-recommended concentrations of insecticides. Insecticide-exposed females produced substantially fewer and more male-biased offspring, accounting for an average of about 28% cumulative loss in parasitoid reproductive capacity per generation. The magnitude of sublethal effects was significantly affected by insecticide mode of action, with broad-spectrum insecticides being particularly harmful to parasitoid reproductive performance. Transgenic crops and toxins derived from such plants were generally associated with weaker sublethal effects than majority of synthetic insecticides. Nevertheless, species responses, even to the same insecticides and transgenic crops, showed high variability, cautioning against extrapolating results from individual studies to a wider range of species. Overall, our results indicate that sublethal side-effects on parasitoid reproductive performance represent a significant and widespread cost of insecticides that should explicitly be taken into account when evaluating their harmfulness. Linking laboratory results to field situations remains a key challenge for future research.

Lethal and sublethal effects of several formulations of azadirachtin on IPM Impact R&D colonies of the bumblebee Bombus terrestris (Hymenoptera: Apidae)

The effects of different dose rates of the most important commercially available formulations of azadirachtin and technical powder of azadirachtin were tested on Bombus terrestris, using a new laboratory method on full standardised IPM Impact R&D colonies, starting with a mother queen and 20 callows. The maximum field recommended concentration (MFRC) was applied in the first series of tests through topical, oral pollen and oral sugar water treatment. A sequential dilution testing scheme was used, by decreasing the dose rate each time with 1/10 of the concentration of the previous trial, if triggered, until no significant effects were recorded any more. The survival of the mother queen and initial workers, the total number of formed workers/drones at the end of the test and the number of new born gynes and queen brood were determined as the most important end points. For the evaluation of the results the data were calculated and categorized in the IOBC side-effect classes, used for laboratory trials. This study confirms the practical experience and the previous laboratory trials that no negative toxic or sublethal effects may occur in practice with legally registered formulations of azadirachtin on Bombus terrestris while spraying this botanical insecticide at the recommended and authorised dose rates. Furthermore, during this research study it was found that an illegal formulation of azadirachtin, based on a naphta petroleum which has been withdrawn several years before the study was carried out, was used in the study of Barbosa, W.F., De Meyer, L., Guedes, R.N.C. and Smagghe, G. (2015). Analysis of two samples of this applied formulation, in EU and USA laboratories, proved that only a limited amount of azadirachtin -about half of the indicated amount- was contained, while a chlorpyrifos contamination was traced in the formulation.

Spinosad-mediated effects on the walking ability, midgut, and Malpighian tubules of Africanized honey bee workers.

The global decline in Apis mellifera colonies is attributed to multiple factors, including pesticides. The bioinsecticide spinosad was initially recognized as safe for non-target organisms; however, its toxicity has been changing this view. Here, we investigated the survival, behavioral changes, and structural changes in the midgut and Malpighian tubules of A. mellifera treated orally with a spinosad formulation. The field-recommended concentration of spinosad killed 100% of the bees. The 5% and 50% lethal concentrations (LC5 and LC50 , respectively) of spinosad altered the behavioral activity, reducing the walking distance and velocity, and increased the resting time in comparison to the control. The LC50 caused disorganization of the epithelia of tested organs and induced oxidative stress and cell death. The present work provides new insights into the debate about the role of bioinsecticides in the mortality of Africanized honey bees. Even at very low concentrations, the spinosad formulation was toxic to the vital organs midgut and Malpighian tubules and adversely affected walking behavior. This detailed evaluation of the impact of the bioinsecticide on A. mellifera will contribute to the clarification of disturbances probably caused by spinosad formulations, which can be used to develop more sustainable protocols in agriculture. © 2017 Society of Chemical Industry.

Effects of buprofezin and imidacloprid on the functional response of Eretmocerus mundus Mercet

Eretmocerus mundus Mercet is one of the key natural enemies of Bemisia tabaci (Gennadius). In this study, the sublethal effects of LC<sub>25</sub> of imidacloprid and field-recommended concentration of buprofezin on the functional response of E. mundus to different densities of second instar B. tabaci nymphs were evaluated. The results revealed a type III functional response in the control and imidacloprid treatment. The type III functional response was altered into a type II by buprofezin. Although imidacloprid did not alter the type of functional response of E. mundus compared to the control, it negatively affected the handling time and maximum attack rate of the parasitoid. Therefore, the use of this insecticide should be evaluated carefully in IPM programs.

Effects of methoxyfenozide and pyridalyl on the larval ectoparasitoid Habrobracon hebetor

Habrobracon hebetor Say (Hymenoptera: Braconidae) is an ectoparasitoid that is used for inundative biological control of various lepidopteran insect pests. Lethal and sublethal effects of two biorational insecticides, methoxyfenozide and pyridalyl, were evaluated on H. hebetor under laboratory conditions. The adults were exposed to dry insecticide residues that were applied on glass plates. Bioassays showed that the LC50 values of methoxyfenozide and pyridalyl were 155 and 1,226 μg a.i./ml, respectively. The LT50 values of methoxyfenozide and pyridalyl were 2.1 and 3.3 days, respectively. The effects of methoxyfenozide and pyridalyl on larvae were tested using a dip method with field-recommended concentrations of either insecticide. The emergence rates were reduced by 24.4 and 29.3 % for methoxyfenozide and pyridalyl treatments, respectively. In order to assess the sublethal effects of low-lethal concentrations of methoxyfenozide and pyridalyl, adult wasps were exposed to the LC30 concentration of each insecticide, and demographic parameters of live wasps were recorded. Exposure of adults to low-lethal concentrations (LC30) negatively affected the fecundity, fertility, and sex ratio, and also the intrinsic rate of increase (rm), finite rate of increase (λ), generation time (T), and doubling time (DT). The longevity and net reproductive rate (R0) of H. hebetor were not affected by sublethal exposure to these insecticides. The results showed that despite low acute toxicities of both insecticides on larval and adult stages of H. hebetor, they may negatively affect the population of the parasitoid and interfere in IPM programs.

Residual Toxicity of Some Pesticides on the Larval Ectoparasitoid, Habrobracon Hebetor Say (Hymenoptera: Braconidae)

Abstract Habrobracon hebetor Say is an idiobiont and gregarious larval ectoparasitoid of many moths. In this study, the effects of field recommended concentrations (FRC) of seven biorational and conventional pesticides in cotton fields (imidacloprid, thiacloprid, deltamethrin, thiodicarb, carbaryl, abamectin and spinosad) were studied on the larval ectoparasitoid, H. hebetor. Exposure cages were used for the bioassay experiments. The experiments were carried out in the laboratory at 26±1°C, 60±5% relative humidity (RH) and with a photoperiod of 16:8 (L:D). Experiments were done in three replications. The results showed that all pesticide treatments had significant differences compared to the control treatment. The results also showed that synthetic and biorational pesticides had lower toxicity than conventional pesticides. We demonstrated that imidacloprid and thiacloprid had lower adverse effects on the parasitoid and could be used as compatible chemical materials with the parasitoid in Integrated Pest Management (IPM) programs.

Lethal and sublethal effects of imidacloprid and buprofezin on the sweetpotato whitefly parasitoid Eretmocerus mundus (Hymenoptera: Aphelinidae)

The parasitoid Eretmocerus mundus Mercet (Hymenoptera: Aphelinidae) is one of the key natural enemies of Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae). Lethal and sublethal effects of imidacloprid and buprofezin on emergence and key biological and population parameters of E. mundus exposed during different developmental stages were studied. Dose–response bioassays were carried out on adult wasps using a leaf dipping method. The emergence rates of adults were reduced significantly by the field-recommended concentrations of the insecticides. However, the emergence rates were not affected either by the stage of the parasitoid at the time of exposure (larval and pupal stages), and there was no interaction between treatments and time of exposure. No significant mortality of E. mundus adults was observed following buprofezin treatment. The LC50 of imidacloprid on adults was 4.75 ppm. The results showed that the longevity and fecundity of E. mundus adults were reduced significantly by the two insecticides, though the sex ratio of E. mundus offspring was not affected. Population parameters of the parasitoid such as R0, rm and T were also significantly reduced by the insecticides. Our results indicated that, in addition to lethal effects, sublethal effects should also be considered when these insecticides are applied in IPM programs for this pest.

Acute Toxicities and Sublethal Effects of Some Conventional Insecticides on <I>Trichogramma chilonis</I> (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.

Lethal and sublethal effects of buprofezin and imidacloprid on the whitefly parasitoid Encarsia inaron (Hymenoptera: Aphelinidae)

Lethal and sublethal effects of imidacloprid and buprofezin on preimaginal and adult stages of the cotton whitefly parasitoid Encarsia inaron (Walker) (Hymenoptera: Aphelinidae) were investigated in the laboratory. Both insecticides significantly reduced adult emergence when parasitised nymphs, at either larval or pupal stages, were treated with field-recommended concentrations. Buprofezin had no significant effect on adult wasps. The LC 50 value of imidacloprid for E. inaron was 208.9 ppm. Adult longevity and the total progeny number were significantly affected only by imidacloprid when the larvae were treated. Both insecticides had a significant influence on parasitoid daily fecundity depending on the stage of the parasitoid at the time of treatment. Sex ratio of E. inaron offspring was significantly affected by the insecticides. Some life history parameters of the parasitoid were affected by application of the insecticides at the larval and pupal stages. However, neither of the insecticides significantly affected the life table parameters of treated adults. The implications of these results for the integration of biological and chemical control methods are discussed.

Acute and population level toxicity of imidacloprid and fenpyroximate on an important egg parasitoid, Trichogramma cacoeciae (Hymenoptera: Trichogrammatidae)

One focus of integrated pest management (IPM) is the use of biological and chemical control in an optimal way. The availability of selective pesticides is important as is information about both lethal and sublethal effects of pesticides on biocontrol agents. Acute and sublethal effects of imidacloprid and fenpyroximate exposure were studied on adult stage of egg parasitoid Trichogramma cacoeciae Marchal and the emergence rate and life table parameters were determined. The adult wasps were exposed to field recommended concentration (FRC) of the pesticides on glass plates. Field rates of imidacloprid and fenpyroximate caused 100 and 32% adult mortality, respectively. Based on concentration-response experiments, the LC(50) values of imidacloprid and fenpyroximate were 6.25 and 1,949 ppm, respectively. The effect of imidacloprid and fenpyroximate on larvae, prepupae and pupae of the parasitoid was tested by exposing parasitized eggs of Sitotroga cerealella Olivier or Cydia pomonella L. to the FRC. Imidacloprid and fenpyroximate reduced adult emergence by 10.7 and 29%, respectively, when S. cerealella eggs were used as the host and 10.9 and 24.9%, respectively, when C. pomonella eggs were used as the host. Population parameters of emerged adults from treated pre-imaginal stages by FRC of the pesticides were also studied. The parameters were longevity and progeny production of emergent adults and also intrinsic rate of increase (r ( m )), generation time (T) and doubling time (DT). Longevity and progeny production of the emergent adults was not affected by pesticide exposure in comparison to the control. In addition, none of population parameters such as r ( m ), T and DT were affected by pesticide exposure. The intrinsic rate of increase for the control, fenpyroximate and imidacloprid exposed populations were 0.388, 0.374, and 0.372 female offspring per female per day, respectively. Overall, results of this study suggest a relative compatibility between fenpyroximate and T. cacoeciae, but imidacloprid showed deleterious effects on adults of the parasitoid.

Lethal and sublethal effects of preimaginal treatments with two pyrethroids on the life history of the egg parasitoid Telenomus busseolae

The egg parasitoid Telenomus busseolae Gahan (Hymenoptera: Scelionidae) is one of the most important natural enemies of the Mediterranean corn stem borer, Sesamia nonagrioides Lefebvre (Lepidoptera: Noctuidae). The effects of lethal and sublethal concentrations of two commonly used pyrethroids, deltamethrin and cyfluthrin, on emergence, fecundity, longevity, and offspring sex ratio of T. busseolae exposed during different preimaginal stages were studied. The insecticide, the tested concentrations of the insecticide (field-recommended concentration and three dilutions with twofold concentration decreases), and the stage of parasitoid preimaginal development (first and second larval stages and pupae) all significantly influenced the percentage of emergence. Life history parameters of parasitoids exposed to the highest and lowest tested concentrations of the two insecticides (3.0 and 0.375 ml l−1 for cyfluthrin and 0.5 and 0.0625 ml l−1 for deltamethrin) at eight days post-oviposition (pupal stage) were calculated. The intrinsic rate of increase, the total progeny produced, and the net reproductive rate of the parasitoid were all adversely affected by the field-recommended concentrations of at least one insecticide. However, the longevity, the length of the oviposition period, and the offspring sex ratio were unaltered by the two insecticides. The effects of sublethal concentrations of the insecticides, applied at preimaginal stages, on the responses of T. busseolae females to host abdominal scales, were studied in open-arena bioassays. Cyfluthrin altered both the residence time and linear speed of the parasitoid in the host scale-containing areas, whereas deltamethrin had no effect. Our results indicate that, in addition to lethal effects, sublethal effects should also be considered when evaluating insecticide consequences on non-targets.

Effects of Azadirachtin/Neemazal on Different Stages and Adult Life Table Parameters of &lt;I&gt;Trichogramma cacoeciae&lt;/I&gt; (Hymenoptera: Trichogrammatidae)

The effects of azadirachtin/Neemazal on adults, emergence, and life table parameters of Trichogramma cacoeciae Marchal were studied. The adults were exposed to fresh residues of the insecticide applied on glass plates. Based on the dose-response study, the LC50 value was 1330 ppm or 13.3 microg (AI)/ml. The effect of Neemazal on three developmental stages of the parasitoid was tested by dipping parasitized Sitotroga cerealella (Olivier) and Cydia pomonella (L.) eggs at the field-recommended concentration 3, 6, and 9 d after parasitization corresponding to larval, prepupal, and pupal stages. The emergence of adult parasitoids was adversely affected in both hosts, but the adverse effect was more in S. cerealella eggs compared with C. pomonella. The adult emergence was reduced by 73.3 and 33.76% in Sitotroga and Cydia eggs compared with controls, respectively. Longevity and progeny production of the emergent adults did not differ significantly from control. Neemazal affected stable population parameters (r(m), T, and DT) significantly. The intrinsic rate of increase for the control and Neemazal-exposed populations was 0.340 and 0.335 female offspring per female per day, respectively. Because some of postemergence life table parameters of adults were significantly reduced by the insecticide treatment, emergence rate of the parasitoid from treated eggs is not an adequate measure of ecological selectivity, and field studies are needed to determine the actual impact of neem on T. cacoeciae.

Effects of azadirachtin/Neemazal on different stages and adult life table parameters of Trichogramma cacoeciae (Hymenoptera: Trichogrammatidae).

The effects of azadirachtin/Neemazal on adults, emergence, and life table parameters of Trichogramma cacoeciae Marchal were studied. The adults were exposed to fresh residues of the insecticide applied on glass plates. Based on the dose-response study, the LC50 value was 1330 ppm or 13.3 microg (AI)/ml. The effect of Neemazal on three developmental stages of the parasitoid was tested by dipping parasitized Sitotroga cerealella (Olivier) and Cydia pomonella (L.) eggs at the field-recommended concentration 3, 6, and 9 d after parasitization corresponding to larval, prepupal, and pupal stages. The emergence of adult parasitoids was adversely affected in both hosts, but the adverse effect was more in S. cerealella eggs compared with C. pomonella. The adult emergence was reduced by 73.3 and 33.76% in Sitotroga and Cydia eggs compared with controls, respectively. Longevity and progeny production of the emergent adults did not differ significantly from control. Neemazal affected stable population parameters (r(m), T, and DT) significantly. The intrinsic rate of increase for the control and Neemazal-exposed populations was 0.340 and 0.335 female offspring per female per day, respectively. Because some of postemergence life table parameters of adults were significantly reduced by the insecticide treatment, emergence rate of the parasitoid from treated eggs is not an adequate measure of ecological selectivity, and field studies are needed to determine the actual impact of neem on T. cacoeciae.