الفهرس 
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Abstract
The whitefly,Bemisia.tabaciGennadius(Hemiptera:Aleyrodidae)is one of the most intractable and worldwide damaging and injurious top hundred pests attacking a wide range of important crops, vegetables and ornamentals all over the world (Denholmet al., 1996; Perring , 2001; Carabaliet al., 2005) . It is highly polyphagous, damaging a broad range of food and non- food crops by direct feeding, excretion of honeydew and transmission of over 100 plant virus (Jones, 2003). Whiteflies are small insects with piercing- sucking mouth parts in which both immature and adult stages feed on the underside of leaves. The cycle of whiteflies includes egg, four nymph stages and the adult stage. Most species of whiteflies develop from egg to adult within 25- 50 days under field conditions and there could be at least six generations per year (Byrne and Bellows, 1991).
In EgyptB.tabaci was not considered a significant pest until the 1990s. Since then it had been found to be widely distributed on vegetables and cotton crop and it had become a major pest and a threat to vegetable and cotton production.
The aim of the present study was to investigate the following:
6- Evaluation of the efficacy of several insecticides against adult and nymph B.tabaci on three vegetables (cucumber, tomato and cabbage) under field conditions.
7- Monitoring of resistance to different insecticides in three field strains of B.tabaciduring 2010 – 2012 cotton seasons.
8- Study the development of resistance in B.tabaci against three insecticides with novel modes of action.
9- Investigate the pattern of cross- resistance to different insecticides in three parent strains and three insecticides-selected strains of B.tabaci.
10- Determination of esterase activity as well asprotein pattern which be involved in resistance in three field strains of B.tabaci during 2010- 2012 cotton seasons.
1- Efficacy of several insecticides against whiteflyB.tabaci
This study was to evaluate the efficacy of eight insecticides against the whiteflyB.tabaci on three plants treated with foliar application at recommended application rate under filed conditions at Agriculture Research Station,Etai El-Baroud in Behera Governorate in season 2014. The three plants used in this study were cucumber (Cucumissativus L.), tomato (Lycopersicomesculentum mill) and cabbage (Brassica oleracea var.).The insecticides used were the neonicotinoidsacetamiprid (Mospilan), thiamethoxam (Actara), imidacloprid (Best), dinotefuran (Oshin); the organophosphate pirimiphos methyl (Actellic); the pyrethroid lambda-cyhalothrin (Karate); the bio insecticides azadirachtin (Achook) and the mineral oil (Cap-2). The efficacy of these insecticides was evaluated at 1, 5 and 10 days after treatment (DAT).The results indicated that all insecticides were very highly effective against both adult and nymph of whitefly either on cucumber, tomato or cabbage plants at 1DAT, where the reduction percentages in both two stages ranged between 98% - 100%, except with acetamprid (96 %, 97% and 97%) and thiamethoxam (93%, 95% and 94%) against adult on three plants, respectively, and also acetamiprid (96% and 97%) and thiamethoxam (94% and 93%) against nymph on cucumber and cabbage plants, respectively. On the other hand, no significant differences in adult or nymph population on three plants were observed among insecticides, except with thiamethoxam against adult and nymph and acetamiprid against nymph on both of cucumber and cabbage plants which showed significantly lower in reduction percentages in population than other insecticides.
The efficacy of all insecticides against adult or nymph on three plants had declined at 5 DAT. The reduction percentages in population varied from one insecticide to another, between two stages and among three plants, As for adult, the reduction percentages ranged between 52% - 65% on cucumber plants, 75% - 81% on tomato plant and 49% - 75% on cabbage plant, while in case of.