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item Simmons, Alvin

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/16/2002
Publication Date: 10/22/2002
Citation: Simmons, A.M., Abd-Rabou, S., Mccutcheon, G.S. 2002. Incidence of parasitoids and parasitism of Bemisia tabaci (Homoptera: aleyrodidae) in numerous crops. Environmental Entomology. 31(6):1030-1036.

Interpretive Summary: The B-strain of the sweetpotato whitefly is a pest in many crops. Knowledge about beneficial organisms that attack the whitefly can help in developing ways of controlling this pest with less insecticides. A study was conducted on the activity of a wasp parasite of this whitefly in several vegetable and other crops. Tests were done in the greenhouse with 7 crops and in the field (in Egypt) with 16 crops. In the greenhouse, a wasp parasite, Encarsia pergandiella, was most abundant on cowpea, followed by cotton. The wasps foraged on both leaf surfaces, but their behavior was different on the different crops and their behavior changed during the day. From sunrise to the middle of the day, less time was spent on the top of leaves and more time was spent on the bottom of leaves. Releases of laboratory-reared wasp parasites, Eretmocerus mundus, into field crops increased the attack of the parasites on the whiteflies. Some crops (such as, two cole crops, and beet) were more likely to have more parasites and parasite-killed whiteflies than other crops (such as, cucumber, eggplant and tomato). Results from this research will be useful in the enhancement and conservation of parasites of whiteflies.

Technical Abstract: Understanding the relationship of parasitoids with their insect hosts and crop plants is needed to develop good management strategies for Bemisia tabaci (Gennadius), a whitefly pest. The abundance and establishment of parasitoids of B. tabaci B-biotype were tested with taxonomically diverse plants of vegetable and other species in the greenhouse (7 plant species) and in the field (16 plant species in Egypt). Greenhouse tests were conducted on plants free of whitefly nymphs to avoid any influence of nymphs on the parasitoid behavior, and field tests were conduced in crops with feral populations of B. tabaci. In the greenhouse, the parasitoid, Encarsia pergandiella Howard, was most abundant on Vigna unguiculata (L.) Walpers, followed by Gossypium hirsutum L. The propensity for this parasitoid to forage on the bottom leaf surface compared with the top surface varied among crops (45-90% were on the bottom leaf surface) and over time (50% were on the bottom leaf surface around sunrise, whereas 90% were on the bottom surface by mid-day). Inundative release of laboratory-reared parasitoids, Eretmocerus mundus (Mercet), into field crops increased parasitization rates. Based on comparisons within plant species, some crops (e.g., two Brassica species, and Beta vulgaris L.) were more conducive to parasitoid population increase and parasitism of B. tabaci than other crops (e.g., Cucumis sativus L., Solanum melongena L, and Lycopersicon esculentum Miller). Findings from this research may be useful in the enhancement and conservation of parasitoids of Bemisia.