Compatibility of Spinosad, Tebufenozide and Azadirachtin with Eggs and Pupae of the Predator Chrysoperla carnea (Stephens) Under Laboratory Conditions

Under laboratory conditions, the toxicity of three novel insecticides, spinosad (Tracer ® ), tebufenozide (Mimic ® ) and azadirachtin (Align ® ), was tested against eggs and pupae of the predator Chrysoperla carnea (Stephens). In a first series of assays, eggs were dipped in an aqueous concentration and no ovicidal activity was scored for the three insecticides. In the second, when females were ovipositing on treated substrate for 24 h, fecundity and hatching percentages were similar as compared to controls and the offspring developed normally until the adult stage. However, spinosad, at the highest concentrations tested, caused a slight, significant reduction in the adult life span and fecundity. In a third series of experiments, pupae developed into normal adults after topical treatment for the three insecticides. Herewith, a pharmacokinetic study indicated low accumulation in the body after pupal cuticle penetration when administrating 14 C-labelled insecticide. Fourthly, pupation of last-instar larvae in treated substrate was normal for spinosad and tebufenozide. Only azadirachtin caused a slight reduction in the number of pupae and adults; however, fecundity and fertility of surviving adults was normal. In conclusion, the current results indicate that the three insecticides are not toxic to eggs and pupae of C. carnea .     

Effect of insecticides on Trichogramma exiguum (Trichogrammatidae: Hymenoptera) preimaginal development and adult survival

The effect of insecticides on Trichogramma exiguum Pinto & Platner emergence, adult survival, and fitness parameters was investigated. Insecticides tested were lambda cyhalothrin, cypermethrin, thiodicarb, profenophos, spinosad, methoxyfenozide, and tebufenozide. All insecticides, with the exception of methoxyfenozide and tebufenozide, adversely affected Trichogramma emergence from Helicoverpa zea (Boddie) host eggs when exposed at different preimaginal stages of development (larval, prepupal, or pupal). Regardless of the developmental stage treated, none of the insecticides tested had a significant effect on the sex ratio or frequency of brachyptery of emerged females. However, the mean life span of emerged T. exiguum females significantly varied among insecticide treatments, and was significantly affected by the developmental stage of parasitoid when treated. Based on LC50 values, spinosad and prophenofos were the most toxic compounds to female T. exiguum adults, followed by lambda cyhalothrin, cypermethrin, and thiodicarb. Insecticides field-weathered for four to 6 d on cotton leaves showed no activity against female T. exiguum adults.     

Significance of absorption, oxidation, and binding to toxicity of four ecdysone agonists in multi-resistant cotton leafworm

Treatment of last-instar larvae of multi-resistant cotton leafworm Spodoptera littoralis with four dibenzoylhydrazines, methoxyfenozide (RH-2485), tebufenozide (RH-5992), halofenozide (RH-0345), and RH-5849, resulted in premature molting leading to death. Methoxyfenozide was the most toxic followed by tebufenozide, halofenozide, and RH-5849. To explain differences in toxicity, especially between multi-resistant and laboratory strains, absorption in the body tissues and oxidative metabolism were tested with 14C-labeled ecdysone agonist and a Lineweaver-Burk assay, respectively. Then to address different compound potencies in multi-resistant strains, the potency of the four ecdysone agonists was measured based on their ability to mimic the natural insect molting hormone, 20-hydroxyecdysone (20E) by inducing evagination in isolated imaginal wing discs. Using monoclonal antibody 9B9, the presence of ecdysteroid receptors in imaginal discs in vitro was confirmed. In parallel, Scatchard plot analysis with whole imaginal wing discs cultured with different concentrations of 3H-labeled ponasterone A indicated no significant difference in affinity and in number of target sites for binding between multi-resistant and susceptible laboratory strains. The four compounds tested caused the effect as agonists of 20E in vitro, and typically the order of their toxicities (LC50s) corresponded with that for evagination-induction with whole imaginal discs.     

Lethal and sublethal effects of selected insecticides and an insect growth regulator on the boll weevil (Coleoptera: Curculionidae) ectoparasitoid Catolaccus grandis (Hymenoptera: Pteromalidae)

A laboratory culture of Catolaccus grandis (Burks), an ectoparasitoid of the boll weevil, Anthonomus grandis grandis Boheman, was exposed to lethal and sublethal doses of insecticides and an insect growth regulator using a spray chamber bioassay. Materials tested were azinphos-methyl, endosulfan, fipronil, malathion, cyfluthrin, dimethoate, spinosad, methyl parathion, acephate, oxamyl, and tebufenozide. At full rates, spinosad was significantly less toxic to female C. grandis than other treatments except endosulfan. Fipronil and malathion were significantly more toxic to females than other treatments. Most of the chemicals tested were highly toxic to male C. grandis; spinosad was least toxic. At reduced rates, most of 4 selected chemicals tested were low in toxicity to C. grandis; however, a reduced rate of malathion was significantly more toxic to females than other treatments. No C. grandis pupae developed from parasitism during a 24-h treatment period with malathion or spinosad. The sex ratio of progeny from sprayed adults appeared to be unaffected by the treatments.     

Effects of three modern insecticides, pyriproxyfen, spinosad and tebufenozide, on survival and reproduction of Chrysoperla carnea adults

Three novel insecticides, pyriproxyfen, spinosad and tebufenozide, were evaluated for their effect on survival and reproduction of Chrysoperla carnea adults using two methods of exposure: direct contact and ingestion. Pyriproxyfen and tebufenozide proved to be harmless to adult survival, whereas spinosad 72 h after treatment reduced the number of adults by 39.8% and 87.2% in topical and ingestion treatment at the maximum concentration recommended (800 mg a.i. litre^?1). Fecundity was not affected irrespective of the insecticide or time of application (before or after the onset of oviposition). Concerning fertility, only pyriproxyfen exerted a negative effect on hatching when the eggs were deposited by females treated by ingestion in the post‐oviposition period at the highest concentration tested (150 mg a.i. litre^?1).     

Effect of insecticides on Tiphia vernalis (Hymenoptera: Tiphiidae) oviposition and survival of progeny to cocoon stage when parasitizing Popillia japonica (Coleoptera: Scarabaeidae) larvae

The effect of insecticides on oviposition of Tiphia vernalis Rohwer and subsequent survival of parasitoid progeny to the cocoon stage was determined in the laboratory by using larval Japanese beetle, Popillia japonica Newman, as the host. Insecticides tested were imidacloprid, thiamethoxam, halofenozide, chlorpyrifos, and carbaryl at labeled rates. Female T. vernalis were allowed 2 d to parasitize P. japonica larvae after the parasitoids had received a 4-d exposure to insecticide-treated soil. Another group of female T. vernalis were allowed 2 d to parasitize P. japonica larvae that had been exposed to insecticide-treated soil for 3-4 d. Percentage of parasitism of P. japonica larvae in these trials after exposure of adult parasitoids to carbaryl, chlorpyrifos, halofenozide, or imidacloprid-treated soil (23.3-50.0%) or adult parasitoids to chlorpyrifos, halofenozide, or imidacloprid-treated grubs (33.0-56.7%) was not negatively affected relative to the control treatment (21.7-54.2%). A third group of adult T. vernalis and P. japonica larvae were simultaneously exposed to chlorpyrifos or carbaryl treatments. Percentage parasitism in these trials was lower for T. vernalis adults exposed to the chlorpyrifos and carbaryl (15.0-25.0%) relative to the control (57.5-62.5%) with the exception of one trial with carbaryl (40.0%). However, exposure of the parasitoid and P. japonica to chlorpyrifos 0.5X, carbaryl 0.5X, imidacloprid, halofenozide, or thiamethoxam in several trials resulted in parasitism that was equivalent or greater than (45.0-80.0%) the untreated control (57.5-62.5%). Japanese beetle larval mortality in these trials was greater in the insecticide and parasitoid combination (97.5-100.0%) than with insecticides alone (45.0-100.0%). Percentage of survival of T. vernalis progeny to the cocoon stage was not negatively affected by a 4-d adult parasitoid exposure to carbaryl and chlorpyrifos treated soil (11.7-16.7% versus 18.3% control) or a 2-d exposure to P. japonica-treated larvae (16.7-18.3% versus 28.3% control). However, simultaneous exposure of T. vernalis progeny and P. japonica larvae to chlorpyrifos- and carbaryl-treated soil resulted in no parasitoids surviving to the cocoon stage. Between neonicotinoids, thiamethoxam had more adverse impact on percentage parasitism (52.5%) and survival to the cocoon stage (10.0%) than imidacloprid (80.0 and 32.5%, respectively). Results of this study indicate soil incorporation of imidacloprid and halofenozide had minimal effect on the number of P. japonica larvae parasitized by T. vernalis or survival of T. vernalis progeny to the cocoon stage; therefore, they are more suitable for use with T. vernalis. In contrast, chlorpyrifos, carbaryl, and thiamethoxam lowered the number of T. vernalis progeny surviving to the cocoon stage, and carbaryl and chlorpyrifos reduced the number of P. japonica larvae parasitized. The soil incorporation of insecticides is discussed as one explanation for the minimal effects of some insecticides on T. vernalis.     

Compatibility of endoparasitoid Hyposoter didymator (Hymenoptera: Ichneumonidae) protected stages with five selected insecticides

Hyposoter didymator (Thunberg) (Hymenoptera: Ichneumonidae) is a koinobiont endoparasitoid that emerges from the parasitization of economically important noctuid pests. H. didymator also is considered one of the most important native biocontrol agents of noctuids in Spain. Side effects of five insecticides with very different modes of action (fipronil, imidacloprid, natural pyrethrins + piperonyl butoxide, pymetrozine, and triflumuron) at the maximum field recommended rate in Spain were evaluated on H. didymator parasitizing Spodoptera littoralis (Boisduval) larvae and pupae of the endoparasitoid. Parasitized larvae were topically treated or ingested treated artificial diet. Parasitoid cocoons were topically treated. Host mortality when parasitized larvae were treated, as well as further development of the parasitoid surviving (e.g., percentage of cocoons spun, adult emergence, hosts attacked, and numbered progeny) were determined. Toxicity after treatment of parasitized larvae differed depending on the mode of exposure and insecticide. Fipronil was always highly toxic; imidacloprid killed all host insects by ingestion, but it was less toxic to both host and parasitoids, when administered topically; natural pyrethrins + piperonyl butoxide and triflumuron showed differing degrees of toxicity, and pymetrozine was harmless. Parasitoid cocoons provided effective protection against all the insecticides, except fipronil.     

Toxicity and kinetics of spinosad in different developmental stages of the endoparasitoid <Emphasis Type="Italic">Hyposoter didymator</Emphasis> (Hymenoptera: Ichneumonidae) and its host <Emphasis Type="Italic">Spodoptera littoralis</Emphasis> larvae (Lepidoptera: Noctuidae)

The toxicity of spinosad was evaluated using the RaPID Assay^® Spinosad immunosorbent assay in different developmental stages of the parasitoid, Hyposoter didymator, and in its host, fourth-instar larvae of the cotton leafworm Spodoptera littoralis. Spinosad was applied directly to pupae and adults of H. didymator (ingestion or topical application) or to the immature stages of the parasitoid via the host larvae. Low amounts of spinosad were recovered from S. littoralis host larvae after topical treatment, and the compound was mainly retained in the hemolymph. Amounts of spinosad detected in third-instar larvae of H. didymator, pulled out from the hemolymph of parasitized S. littoralis larvae, were 85 pg (3.57 ng a.i./g body weight) in dead larvae, and 82 pg (3.42 ng a.i./g body weight) in alive individuals. After topical treatment of H. didymator cocoons, most of the compound was retained in the silken cocoon, preventing contamination of the pupa. Also in the parasitoid adults, relatively low amounts of spinosad were accumulated in the body overall, but half of all the insecticide recovered was found in the ovaries. The kinetic results obtained help to better understand the toxicity of spinosad in the complex S. littoralis–H. didymator, and to ascertain the compatibility between spinosad and the parasitoid for optimizing the control of lepidopteran pests.     

Effect of temperature on efficacy of insecticides to differential grasshopper (Orthoptera: Acrididae)

The effect of temperature on activity of insecticides for controlling grasshoppers in leafy green vegetables was evaluated. Insecticides evaluated had differing modes of action and included diflubenzuron, azadirachtin, Beauveria bassiana, spinosad, endosulfan, esfenvalerate, and naled. We evaluated these insecticides for efficacy to third instars of differential grasshopper, Melanoplus differentialis (Thomas), at temperatures ranging from 10 to 35 degrees C. In the laboratory, treatment with esfenvalerate resulted in 100% mortality at temperatures of 10 to 35 degrees C, and efficacy was not temperature dependent. Treatment with spinosad resulted in similar mortality as with esfenvalerate at all temperatures except 10 degrees C. The activity of B. bassiana was greatest at 25 degrees C and was adversely affected by high and low temperatures. Treatment with diflubenzuron resulted in increased mortality at high temperatures, and at 35 degrees C its activity was similar to that of esfenvalerate and spinosad. The activity of azadirachtin ranged from 19 to 31% and was not influenced by temperature. In field studies, spinosad, diflubenzuron, and esfenvalerate provided differing levels of mortality both at application and when nymphs were exposed to 1-h-old residues. However, only spinosad and diflubenzuron provided similar levels of mortality when nymphs were exposed to 24-h-old residues. The residual activity of endosulfan, naled, esfenvalerate, and spinosad decreased with increasing time (0-24 h) after exposure to sunlight and high summer temperatures. Compared with other insecticides, naled had a short residual activity period and activity was dependent upon immediate contact with the nymphs or their substrate. B. bassiana was inactive under high temperatures and intense sunlight as occurs in summer.     

Optimum and maximum host sizes at parasitism for the endoparasitoid Hyposoter didymator (Hymenoptera: Ichneumonidae) differ greatly between two host species

Host size is considered a reliable indicator of host quality and an important determinant of parasitoid fitness. Koinobiont parasitoids attack hosts that continue feeding and growing during parasitism. In contrast with hemolymph-feeding koinobionts, tissue-feeding koinobionts face not only a minimum host size for successful development but also a maximum host size, because consumption of the entire host is often necessary for successful egression. Here we study interactions between a generalist tissue-feeding larval endoparasitoid, Hyposoter didymator Thunberg (Hymenoptera: Ichneumonidae) and two of its natural hosts, Spodoptera exigua Hübner and Chrysodeixis chalcites Esper (Lepidoptera: Noctuidae). Larvae of C. chalcites are up to three times larger than corresponding instars of S. exigua and also attain much higher terminal masses before pupation. We hypothesized that the range of host instars suitable for successful parasitism by H. didymator would be much more restricted in the large host C. chalcites than in the smaller S. exigua. To test this hypothesis, we monitored development of H. didymator in all instars of both host species and measured survival, larval development time, and adult body mass of the parasitioid. In contrast with our predictions, C. chalcites was qualitatively superior to S. exigua in terms of the survival of parasitized hosts, the proportion of parasitoids able to complete development, and adult parasitoid size. However, in both hosts, the proportion of mature parasitoid larvae that successfully developed into adults was low at the largest host sizes. Our results suggest that qualitative, as well as quantitative, factors are important in the success of tissue-feeding parasitoids.     

Toxicity of two ecdysone agonists, halofenozide and methoxyfenozide, against the multicoloured Asian lady beetle Harmonia axyridis (Col., Coccinellidae)

Abstract: The insecticidal activity of two ecdysone agonists, methoxyfenozide (RH-2485) and halofenozide (RH-0345), was tested against last-instar larvae of the natural predator Harmonia axyridis (Col., Coccinellidae). In addition, the relative weight gain of the larvae after application was followed. Both products proved to be equally toxic at concentrations of 25, 50 and 100 mg/l. The ecdysteroidal activity of the compounds caused premature induction of larval moulting, cessation of feeding and incomplete pupation in affected larvae. Although, compared with previous results with methoxyfenozide and halofenozide in target pests such as the Colorado potato beetle, Leptinotarsa decemlineata , these compounds caused mortality only after application at relatively high concentrations.     

Lethal and sublethal effects of insecticide residues on Orius insidiosus (Hemiptera: Anthocoridae) and Geocoris punctipes (Hemiptera: Lygaeidae)

Laboratory-reared predators, the insidious flower bug, Orius insidiosus (Say), and big-eyed bug Geocoris punctipes (Say), were exposed to 10 insecticides, including three newer insecticides with novel modes of action, using a residual insecticide bioassay. These species are important predators of several economic pests of cotton. Insecticides tested were: azinphos-methyl, imidacloprid, spinosad, tebufenozide, fipronil, endosulfan, chlorfenapyr, cyfluthrin, profenofos, and malathion. There was considerable variation in response between both species tested to the insecticides. Tebufenozide and cyfluthrin were significantly less toxic to male O. insidiosus than malathion. Tebufenozide was also significantly less toxic to female O. insidiosus than malathion. Imidacloprid, tebufenozide, and spinosad were significantly less toxic to male G. punctipes than chlorfenapyr, endosulfan, and fipronil. Spinosad, tebufenozide, and azinphos-methyl were significantly less toxic to female G. punctipes than fipronil and endosulfan. Fecundity of O. insidiosus was significantly greater in the spinosad treatment compared with other treatments including the control. Consumption of bollworm, Helicoverpa zea (Boddie), eggs by O. insidiosus was significantly lower in the fipronil, profenofos, and cyfluthrin treatments compared with other treatments including the control. Consumption of H. zea eggs by G. punctipes was significantly lower in the malathion, profenofos, endosulfan, fipronil, azinphos-methyl, and imidacloprid treatments compared with the control. Egg consumption by G. punctipes was not significantly different in the tebufenozide treatment compared with the control. The lower toxicity of spinosad to G. punctipes is consistent with other reports. Based on these results, the following insecticides are not compatible with integrated pest management of cotton pests: malathion, endosulfan, profenofos, fipronil, and cyfluthrin; while imidacloprid, tebufenozide, azinphos-methyl, and spinosad should provide pest control while sparing beneficial species.     

Susceptibility of the predatory stinkbug <Emphasis Type="Italic">Picromerus bidens</Emphasis> to selected insecticides

The Palaearctic stinkbug Picromerus bidens L. (Heteroptera: Pentatomidae) has been considered as a potential biocontrol agent of several defoliator pests in various agricultural and forest ecosystems. It may therefore be a valuable alternative for the Nearctic pentatomid Podisus maculiventris (Say) (Heteroptera: Pentatomidae), the augmentative use of which has largely been abandoned in Europe given its possible environmental impact as an exotic polyphagous predator. However, no study has yet documented the impact of insecticides on P. bidens, which is essential to evaluate the possible combination of this predatory pentatomid with current insecticide applications in integrated pest management (IPM) programmes. This study reports on laboratory experiments investigating the susceptibility of P. bidens to five insecticides with different modes of action: the pyrethroid deltamethrin, the diacylhydrazine methoxyfenozide, the juvenile hormone mimic pyriproxyfen, the spinosyn spinosad, and the neonicotinoid imidacloprid, all of which are used to control defoliator pests. Fourth-instar nymphs and female adults of the predator were exposed to formulated materials of the insecticides by residual contact. Methoxyfenozide and spinosad did not cause significant mortality to 4th instars and female adults of P. bidens. In contrast, deltamethrin and imidacloprid were harmful to nymphs and adults of the predator, with LC₅₀ values ranging between 1.5 and 9.9 mg a.i./l. Pyriproxyfen was toxic to 4th instars with an LC₅₀ value of 13.9 mg a.i./l but did not affect female adults. Reproduction and longevity of P. bidens were not adversely affected when the predator was exposed to field concentrations of spinosad, methoxyfenozide, or pyriproxyfen, or sublethal concentrations (around LC₁₀) of deltamethrin and imidacloprid. The results from residual contact experiments suggest that methoxyfenozide, spinosad, and to a lesser extent, pyriproxyfen may be compatible with P. bidens in an IPM programme. Further experiments assessing food chain toxicity of these compounds should offer a more complete picture of their selectivity.     

Development, oviposition, and mortality of Neoseiulus fallacis (Acari: Phytoseiidae) in response to reduced-risk insecticides

Eight reduced-risk insecticides (acetamiprid, thiamethoxam, imidacloprid, thiacloprid, methoxyfenozide, pyriproxyfen, indoxacarb, and spinosad) and three conventional insecticides (azinphosmethyl, fenpropathrin, and esfenvalerate) were tested against Neoseiulus fallacis (Garman) (Acari: Phytoseiidae), the most abundant predacious mite in North Carolina apple (Malus spp.) orchards. To assess the effect of insecticides on development and mortality of N. fallacis immatures, 12-h-old eggs were individually placed on bean leaf disks previously dipped in insecticide solutions. Tetranychus urticae Koch (Acari: Tetranychidae) females were added as a food source. None of the reduced-risk insecticides significantly affected immature N. fallacis compared with the control; however, the pyrethroids esfenvalerate and fenpropathrin were highly toxic to immatures. To evaluate the effect of insecticides on mortality and oviposition of adult N. fallacis, 7- to 8-d-old females were confined on insecticide-treated bean leaves with Malephora crocea (Aizoaceae) pollen added as a food source. Spinosad resulted in the highest mortality, whereas azinphosmethyl, acetamiprid, fenpropathrin, and imidacloprid were moderately toxic, and mortality from esfenvalerate, indoxacarb, thiacloprid, methoxyfenozide, pyriproxyfen, and thiamethoxam did not differ significantly from the control. Oviposition was affected in a similar manner, with the exception of acetamiprid that did not affect oviposition, and thiamethoxam that reduced oviposition.     

Synergism of diacylhydrazine insecticides with metyrapone and diethylmaleate

Abstract:  The two metabolic synergists, metyrapone (2-methyl 1,2-di-3-pyridyl-1-propanone) and diethylmaleate could increase the toxicity of the three most recent diacylhydrazines, representing a novel group of insect growth regulators (IGRs). These components are known as respective inhibitors of oxidative and glutathione S-transferase enzymes. Larvicidal toxicity was tested in the laboratory by oral treatment against last-instar larvae of the Colorado potato beetle Leptinotarsa decemlineata (Say) and of the beet armyworm Spodoptera exigua (Hübner). The obtained results should enable to improve the activity of tebufenozide, methoxyfenozide and halofenozide, and it may be used to suggest potential mechanisms for resistance against this novel group of IGRs, that is important to counteract cross-resistance with other insecticide groups.     

Effects of insect growth regulators on citrus mealybug parasitoid Leptomastix dactylopii (Hymenoptera: Encyrtidae)

In this study, we measured the effects of three commonly used insecticides classified as insect growth regulators, on the encyrtid parasitoid Leptomastix dactylopii (Howard) when parasitizing citrus mealybug, Planococcus citri (Risso). Kinoprene, pyriproxyfen, and azadirachtin were evaluated in both petri dish and a cage experiment at label-recommended rates to measure their effects on the mortality, parasitization rate, and sex ratio of L. dactylopii. Insecticides were applied to petri dishes and plants either immediately before, 24 h before, or 48 h before release of the parasitoid. Kinoprene applied 24 h before parasitoid release caused 100% mortality of L. dactylopii in petri dishes within 48 h. Mortality rates for L. dactylopii exposed to azadirachtin and pyriproxyfen did not exceed 5% regardless of release time. There were no release time x insecticide interactions on L. dactylopii parasitization rate. The insecticide alone, however, did significantly affect parasitization rates of L. dactylopii on P. citri; the kinoprene treatment significantly reduced L. dactylopii parasitization rates compared with azadirachtin and pyriproxyfen. In a cage experiment with coleus, Solenostemon scutellaroides (L.) Codd, applications of both pyriproxyfen and kinoprene resulted in fewer P. citri parasitized by L. dactylopii than azadirachtin or the control. The sex ratio was equivalent in the petri dish experiment, whereas in the cage experiment the sex ratio was biased toward males, particularly for the kinoprene treatment. Based on the results from this study, we suggest that kinoprene is not compatible with releases of L. dactylopii to control citrus mealybugs.     

Assessing risks of pesticides targeting lepidopteran pests in cruciferous ecosystems to eggs parasitoid,Trichogramma brassicae (Bezdenko)

Lethal and sub lethal effects of fresh and old residues of azadirachtin, spinosad, Bacillus thuringiensis var. kurstaki (Bt var. k), and deltamethrin, were evaluated at their recommended field doses against adult and immature stages of Trichogramma brassicae under in vitro conditions. The experiments were carried out at the Entomology section of Division of Crop Protection, ICAR Research Complex for NEH region, Umiam, Meghalaya, in 2012–2013. The effects of different pesticides were determined by bioassays using the residual film method, the diet contamination method, the pupal dip method and the topical application technique. The four pesticides were found harmful to adult T. brassicae after ingestion, however surface contact bioassays revealed that Bt var. k was the least toxic pesticide. Except Bt var. k, other three pesticides were found harmful also to the immature stages of T. brassicae and significantly affected parasitism potential, adult emergence, longevity of adults, and sex ratio of the progeny. Deltamethrin and azadirachtin were the most harmful, even after 15 days of application. Spinosad was found to be relatively safe to T. brassicae after 15 days of application. As Bt appeared to be the least toxic pesticide for T. brassicae, it could be used for the management of severe infestations of lepidopteran pests in cruciferous ecosystems.If essential, spinosad may be used 15 days after parasitoid release, thus minimizing the chances of parasitoid exposure.     

Pesticide selectivity for the insect egg parasitoid <Emphasis Type="Italic">Telenomus remus</Emphasis>

We evaluated the side-effects of insecticides, herbicides and fungicides on adults of the egg parasitoid Telenomus remus (Nixon) under laboratory conditions. The protocol was adapted from that proposed by the Pesticides and Beneficial Organisms Working Group of the International Organization for Biological Control (IOBC) for Trichogramma cacoeciae (Marchal). Chlorpyrifos, acephate, beta-cyfluthrin + imidacloprid, spinosad, and pyrethroids were harmful to the parasitoid, whereas methoxyfenozide, diflubenzuron, and flufenoxuron had no effect. Of the herbicides examined, only glyphosate + imazethapyr and 2,4-D amine were classified as harmless on the first and second days of parasitism; paraquat was the most harmful. Other herbicides were harmless on the first day of parasitism, but caused various levels of reduction of T. remus parasitism on the second day. The fungicides were harmless or only slightly harmful.     

Effect of insecticides on the diamondback moth (Lepidoptera: Plutellidae) and its parasitoid Diadegma insulare (Hymenoptera: Ichneumonidae)

Studies were conducted to evaluate the toxicity of insecticides to adult Diadegma insulare (Cresson) and its host the diamondback moth, Plutella xylostella (L.). Leaf-dip and direct-dip bioassays for diamondback moth larvae and residual bioassays for adults of diamondback moth and D. insulare were used to assess mortalities. Larval mortalities at field rates were significantly higher with carbaryl, permethrin, spinosad, and tebufenozide when compared with Bacillus thuringiensis, or imidacloprid in the larval-dip bioassay 72 h after treatment. In the leaf-dip and residual bioassays, both permethrin and spinosad caused 100% mortalities to diamondback moth larvae and adults, respectively, 72 h after treatment. Of all the materials tested, only B. thuringiensis and tebufenozide were not toxic to D. insulare 24 h after treatment. Spinosad was not toxic to D. insulare 30 min after treatment. However, 100% mortality was observed 8 h after treatment.     

Towards Coleoptera-specific high-throughput screening systems for compounds with ecdysone activity: development of EcR reporter assays using weevil (Anthonomus grandis)-derived cell lines and in silico analysis of ligand binding to A. grandis EcR ligand-binding pocket

Molting in insects is regulated by ecdysteroids and juvenile hormones. Several synthetic non-steroidal ecdysone agonists are on the market as insecticides. These ecdysone agonists are dibenzoylhydrazine (DBH) analogue compounds that manifest their toxicity via interaction with the ecdysone receptor (EcR). Of the four commercial available ecdysone agonists, three (tebufenozide, methoxyfenozide and chromafenozide) are highly lepidopteran specific, one (halofenozide) is used to control coleopteran and lepidopteran insects in turf and ornamentals. However, compared to the very high binding affinity of these DBH analogues to lepidopteran EcRs, halofenozide has a low binding affinity for coleopteran EcRs. For the discovery of ecdysone agonists that target non-lepidopteran insect groups, efficient screening systems that are based on the activation of the EcR are needed. We report here the development and evaluation of two coleopteran-specific reporter-based screening systems to discover and evaluate ecdysone agonists. The screening systems are based on the cell lines BRL-AG-3A and BRL-AG-3C that are derived from the weevil Anthonomus grandis, which can be efficiently transduced with an EcR reporter cassette for evaluation of induction of reporter activity by ecdysone agonists. We also cloned the almost full length coding sequence of EcR expressed in the cell line BRL-AG-3C and used it to make an initial in silico 3D-model of its ligand-binding pocket docked with ponasterone A and tebufenozide.