Effect of Melia azedarach L. Extract on Bemisia argentifolii (Hemiptera: Aleyrodidae) and Its Biocontrol Agent Eretmocerus rui (Hymenoptera: Aphelinidae)

We studied the effects of Melia azedarach L. fruit extracts on survival of Bemisia argentifolii Bellows and Perring nymphs and the parasitoid Eretmocerus rui Zolnerowich and Rose and on whitefly oviposition under laboratory conditions. In an experiment to determine toxicity to second-instar nymphs of aqueous extracts of three different sources of M. azedarch, survival of treated nymphs was significantly lower than survival of untreated control nymphs. In a second experiment to determine the effect of combined treatments involving extract application and exposure to parasitoids, the number of emerged whiteflies was significantly higher from control plants than from any of the combined treatments. Successful parasitism was the lowest when adult parasitoids were introduced after dipping second instars in the extract and when whitefly nymphs were dipped in extract 2 d after parasitism. However, the level of parasitism in parasitized nymphs dipped in extracts 4 and 8 d after parasitism was comparable with that of the control. The number of dead whitefly nymphs in combined treatments declined as the age of whitefly nymphs at application increased, with a concomitant increase in successful parasitism. Combined application of plant extract and parasitoids had an additive effect on whitefly nymphal mortality. In a test of whitefly oviposition, there was no significant difference in number of eggs laid on plants treated with extracts and on control plants. However, significantly fewer whiteflies emerged from eggs laid on treated plants than on control plants, indicating that M. azedarach extracts had affected egg development. Thus, M. azedarach fruit extract and the parasitoid E. rui are compatible and may contribute to lower whitefly populations in an integrated pest management program.