عبدالله نزار علي القصير

ABSTRACT In this study, the efficacy of (hot and cold) water extracts and organic solvent extracts (ethyl alcohol, ethyl acetate, and hexane) of Melia azedarach L (Sapindales: Meliaceae) leaves was assessed as a larvicide for Culex pipiens L. (Dipera: Culicidae). Hot water extract was more potent than cold water extract in larval mortality. Average mortality of first, second, third, and fourth larval instars was 56.7, 52.2, 47.7, and 44.5%, respectively, after 24 h of exposure. The average mortality of the same larval stages from the cold water was 51.1, 45.5, 37.8, and 36.7%, respectively. Significant difference was found in pupal mortality as well. The average mortality of pupae was 34.43% and 41.11% due to cold and hot water extracts, respectively. Similarly, hexane, ethyl acetate, and ethyl alcohol extracts were toxic to pupae and mortality recorded was 32.6, 27.95, and 28.36%, respectively. Hexane extract was comparatively more toxic to larvae than ethyl acetate and ethyl alcohol extracts. The results of the present study emphasize the importance of using toxic components extracted from the plant to control the main vector of many detrimental diseases as well as finding environmentally-friendly and sustainable biopesticides. Furthermore, the results suggested that biocontrol programs should take into consideration the focus on larval stages of C. pipiens when aiming to control this medically important insect. However, further investigation is required to determine the efficacy of M. azedarach leaves extracts on fitness of adult mosquitoes such as female longevity and fecundity and egg hatching rate, especially those developed from larvae and pupae exposed to M. azedarach extracts.

Egg parasitoids have evolved various searching behaviors to facilitate finding and locating their hosts in nature. Plant volatiles and host cues induced by egg deposition may be used by female wasps to detect host eggs. We studied host seeking behavior in Trichogramma papilionis (Hymenoptera: Trichogrammatidae) to different infochemical cues using Y-tube olfactometry. T. papilionis females preferred odors from Helicoverpa zea (Lepidoptera: Noctuidae) eggs compared to Ephestia kuehniella (Lepidoptera: Pyralidae) eggs. When plants were infested with H. zea eggs, T. papilionis preferred infested sunn hemp, Crotalaria juncea, over maize, Zea mays. No preference was observed in plants not infested with H. zea eggs, suggesting T. papilionis showed a positive response to stimuli from sunn hemp plants that might be induced by H. zea oviposition. The difference in plant volatile organic components with and without oviposition was investigated by head-space analysis. Compounds detected at notably higher concentrations in the egg plus plant material samples were found to be consistent with a number of compounds known to be pheromone-associated. Leaves with eggs oviposited on them produced some compounds that were unique compared to untreated plant material, and some of those compounds have known insect pheromone activity.

Parasitoid wasps may rely on chemical volatiles from herbivorous insects and their plant hosts for finding their preferred host. This study was conducted to test the reaction of Trichogramma papilionis Nagarkatti (Hymenoptera: Trichogrammatidae) to chemical volatiles that from host eggs and egg infested plants. Several volatile compounds were selected, singly, and as combinations of chemicals to determine whether these volatile compound blends could enhance orientation responses of T. papilionis wasps toward the source of the stimulus. In a Y-tube olfactometer, female wasps were significantly attracted to only two chemical volatiles among the seven compounds tested. The compounds were: trans-isoeugenol, anisole, β-myrcene, cis-3-Hexenyl butyric acid (bis(2-ethylhexyl) phthalate, bis(2-ethylhexyl) phthalate, acetophenone, and α-farnesene (>95% purity). Only anisole and bis(2-ethylhexyl) phthalate were attractive to T. papilionis wasps when used separately in olfactometer experiments. The wasps showed a significant attraction to a blend of anisole and bis(2-ethylhexyl) phthalate at a ratio of 25 μL/100 μL. There was no significant response to the other bled ratios of that combination of chemicals. Greenhouse studies showed that the wasps were not significantly attracted to anisole alone, but exhibited short-distance attraction to the above blend.

Trichogramma species (Hymenoptera: Trichogrammatidae) are egg parasitoids of a variety of insect pests, especially Lepidoptera, and are often mass reared in large numbers for use in augmentative biological control. Many issues with captive rearing of parasitoids may impact their effectiveness as biological control agents, including inbreeding and loss of fitness within colonies. The goal of this study was to test the effect of female founder population size on the fitness of progeny of T. papilionis over successive generations and quantify any change in their biological performance. Two parasitoid lines were reared for 10 generations using 1, 2, and 10 inseminated founder females each generation. Fitness parameters were measured in each generation including fecundity (number of eggs per female), emergence rate, and sex ratio, under two different rearing temperatures. Parasitoid founder number did not affect the mean number of eggs per female in T. papilionis over ten generations, but emergence rate and sex ratio were significantly reduced in the lower founder number treatments. These results suggest that establishing laboratory colonies with 10 or more founder females will reduce the likelihood of loss of fitness.