azadirachtin and Body-Weight

Because of their natural origin, biopesticides are assumed to be less harmful to beneficial insects, including bees, and therefore their use has been widely encouraged for crop protection. There is little evidence, however, to support this ingrained notion of biopesticide safety to pollinators. Because larval exposure is still largely unexplored in ecotoxicology and risk assessment on bees, an investigation was performed on the lethal and sublethal effects of a diet treated with 2 bioinsecticides, azadirachtin and spinosad, on the stingless bee, Melipona quadrifasciata, which is one of the most important pollinators in the Neotropics. Survival of stingless bee larvae was significantly compromised at doses above 210 ng a.i./bee for azadirachtin and 114 ng a.i./bee for spinosad. No sublethal effect was observed on larvae developmental time, but doses of both compounds negatively affected pupal body mass. Azadirachtin produced deformed pupae and adults as a result of its insect growth regulator properties, but spinosad was more harmful and produced greater numbers of deformed individuals. Only spinosad compromised walking activity of the adult workers at doses as low as 2.29 ng a.i./bee, which is 1/5000 of the maximum field recommended rate. In conclusion, the results demonstrated that bioinsecticides can pose significant risks to native pollinators with lethal and sublethal effects; future investigations are needed on the likelihood of such effects under field conditions.

Topics: Animals; Bees; Behavior, Animal; Biological Control Agents; Body Weight; Drug Combinations; Larva; Lethal Dose 50; Limonins; Macrolides; Pupa

The effect of azadirachtin (AZA), a tetranortriterpene from neem, on the mortality, acetylcholinesterase (AChE) activity, and the development of the ovaries of female brown planthopper (BPH), Nilaparvata lugens (Stål) was tested in laboratory experiments. The lethal concentrations were determined and applied topically to the adult female BPH (LC(50)=0.47 ppm and LC(90)=0.96 ppm). The treated insects exhibited toxic symptoms with a dose-dependent mortality. The LC(50) concentrations were tested against AChE activity of the BPH. The results indicate that AZA significantly inhibits the activity of AChE only at the high dose (P<.0001) compared with control. Adult females that were exposed to AZA showed a significant reduction in weight (23%, 40%, and 64% for 0.1, 0.25, and 0.5 ppm, respectively). Fecundity was also significantly reduced in AZA treatments compared to the control. Histological study of ovary sections revealed abnormalities in follicular epithelial cells due to AZA treatment.

Topics: Acetylcholinesterase; Animals; Body Weight; Cholinesterase Inhibitors; Epithelial Cells; Female; Fertility; Hemiptera; Insecticides; Lethal Dose 50; Limonins; Ovarian Follicle

The blowfly, Chrysomya megacephala (Fabricius), and housefly, Musca domestica Linnaeus, are ubiquitous insects that have the potential to spread a variety of pathogens to humans and livestock. Pest management techniques for populations of these flies are needed. Currently, bioinsecticides, particularly those derived from plant origin, have been increasingly evaluated in controlling populations of medically important insects. In this study, an attempt was made to evaluate the efficacy and biological activity of a commercially available neem extract, containing 0.24% azadirachtin A, against C. megacephala and M. domesitca. Laboratory bioassays were performed using the feeding method of mixing neem solutions with fresh beef, once or multiple times, as food for rearing third instar. The laboratory tests showed that neem products significantly reduced larval and pupal survival, adult emergence, pupal weight, adult wing length, and fecundity on the subsequent generation, in a dose-dependent manner in both species. Efficacy was observed in the first generation and could extend to the second generation. Despite these reductions, reduction in total adult longevity was not evident for larvae fed once on neem solutions with fresh beef, and slightly earlier (approximately 1 week) mortality was observed in both species when they were fed as larvae on multiple doses. Adverse effects of this neem-based product toward M. domestica were slightly greater than those in C. megacephala. These data reinforced the efficacy of neem extract in reduced adult emergence and anti-fecundity in the subsequent generation. However, neem extract induced only low to moderate larval and pupal mortalities.

Topics: Animals; Azadirachta; Body Weight; Diptera; Female; Fertility; Insecticides; Larva; Limonins; Male; Plant Extracts; Pupa; Survival Analysis; Wings, Animal

Anoplophora glabripennis (Motschulsky) (Coleoptera: Cerambycidae) is one of the most serious nonnative invasive forest insects discovered in North America in recent years. A. glabripennis is regulated by federal quarantines in the United States and Canada and is the subject of eradication programs that involve locating, cutting, and chipping all infested trees. Other control methods are needed to aid in eradication and to form an integrated management program in the event eradication fails. We conducted laboratory bioassays to determine the toxicity of two systemic insecticides, azadirachtin and imidacloprid, for potential control of A. glabripennis and the cottonwood borer, Plectrodera scalator (F.) (Coleoptera: Cerambycidae), a closely related native cerambycid. Larvae of both cerambycid species were fed artificial diet with dilutions of azadirachtin or imidacloprid for 14 wk. Both insecticides exhibited strong antifeedant effects and some toxicity against A. glabripennis and P. scalator larvae. For A. glabripennis, the highest larval mortality at the end of the bioassay was 60% for larvae fed artificial diet treated with azadirachtin (50 ppm) or imidacloprid (1.6 ppm). For P. scalator, the highest larval mortality at the end of the bioassay was 100% for larvae fed artificial diet treated with azadirachtin (50 ppm) or imidacloprid (160 ppm). At 14 wk, the LC50 values for P. scalator were 1.58 and 1.78 ppm for azadirachtin and imidacloprid, respectively. Larvae of both species gained weight when fed diet treated with formulation blanks (inert ingredients) or the water control but lost weight when fed diet treated with increasing concentrations of either azadirachtin or imidacloprid. In a separate experiment, A. glabripennis adults were fed maple twigs treated with high and low concentrations of imidacloprid. A. glabripennis adult mortality reached 100% after 13 d on twigs treated with 150 ppm imidacloprid and after 20 d on twigs treated with 15 ppm imidacloprid. There was no visible feeding by A. glabripennis adults on twigs treated at the higher imidacloprid rate, and feeding was significantly reduced for adults placed on twigs treated at the low imidacloprid rate compared with adults on untreated twigs. In summary, imidacloprid and azadirachtin had both antifeedant and toxic effects against A. glabripennis and P. scalator and have potential for use in management programs. Based on our results, the delivery of high and sustained insecticide concentratio

Topics: Acer; Animals; Biological Assay; Body Weight; Coleoptera; Feeding Behavior; Imidazoles; Insect Control; Insecticides; Larva; Lethal Dose 50; Limonins; Neonicotinoids; Nitro Compounds; Plant Stems; Time Factors

Azadirachtin, a biopesticide obtained from neem, was subjected to subchronic toxicological testing to document its safety for use as a pesticide. Azadirachtin technical 12% orally administered to male and female rats at doses of 500, 1000 and 1500 mg/kg/day for 90 days did not produce any signs of toxicity, mortality, changes in tissue weight, pathology and serum and blood parameters. It can be suggested that azadirachtin at the highest dose tested is well tolerated by rats of both sexes. The highest dose, 1500 mg/kg, can be used as a basal dose for the determination of the no-observed-effect level (NOEL) of azadirachtin to calculate its safety margin.

Topics: Administration, Oral; Animals; Antimalarials; Body Weight; Female; Glycerides; Insecticides; Limonins; Male; Molecular Structure; No-Observed-Adverse-Effect Level; Organ Size; Rats; Terpenes; Triterpenes

To evaluate the potential effect of exposure to azadirachtin technical 12% throughout major organogenesis, rats were fed orally with 500, 1000 and 1500 mg/kg/day azadirachtin on gestation days 6-15 and examined for evidence of embryo/fetotoxicity and teratogenic effects. Technical azadirachtin at different doses did not produce any significant adverse effects in reproductive parameters. Significant embryo/fetotoxic effects were not observed at tested dose levels as evidenced by total number of implantations, post-implantation loss and fetal weight. There were no major malformations, while some minor variants found in high doses were not compound or dose related. The absence of anomalies in fetal gross, visceral morphology and skeleton suggests that technical azadirachtin is not teratogenic in rats at the doses tested.

Topics: Animals; Body Weight; Embryo, Mammalian; Female; Fetus; Insecticides; Limonins; Male; Pregnancy; Rats; Reproduction; Skeleton; Teratogens; Triterpenes