The objective of this study was to investigate the potential resistance mechanisms to Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) B biotype, in eight Cucurbita pepo varieties. Attractivity, oviposition preference, and nymphal development were evaluated under greenhouse and laboratory conditions. Variety Bianca was the least attractive to adult whiteflies in multi-choice tests. The whiteflies showed oviposition nonpreference (antixenosis) for Novita Plus, Bianca and Sandy in multi-choice test, and similar results were observed in no-choice tests with varieties Bianca, Novita, Caserta Cac and Sandy. Sandy expressed high antibiosis levels against whitefly nymphs, leading to 63.9% mortality. The high level of resistance in variety Sandy can serve as base for genetic improvement of C. pepo focusing on the development of resistant varieties to B. tabaci B biotype.

Use of plant extracts on whitefly control in tomato grown in greenhouseLooking for alternative methods of control to silverleaf whitefly Bemisia tabaci (Gennadius) biotype B in tomato, attractiveness and oviposition preference tests were accomplished in greenhouse using fourteen aqueous extracts at 3% (weight/volume). The extracts were prepared with parts from Azadirachta indica, Trichilia pallida, Chenopodium ambrosioides, Piper nigrum, Melia azedarach, Ruta graveolens, Ricinus communis, Mentha pulegium, Tagetes erecta, Eucalyptus citriodora, Cymbopogon nardus and Coriandrum sativum. The most efficient extracts in greenhouse were also tested in laboratory to evaluate the possible systemic effect on whitefly nymphs. Tomato plants sprayed with extracts of leaves from M. pulegium, leaves and seeds from A. indica were less attractive to the adults of the insect. Plants sprayed with extracts of leaves from A. indica and leaves + branches from R. communis showed deterrent effects on the insect oviposition, reducing the number of eggs; in an opposite way, the extract of leaves from C. nardus stimulated the whitefly oviposition on the plants. The use of extracts in a systemic way did not affect the whitefly development period (egg-adult). The extracts of seeds and leaves from A. indica and leaves from M. pulegium increased the mortality of nymphs of B. tabaci biotype B.

Field assays were performed to evaluate the attractiveness and the non-preference of whitefly Bemisia tabaci (Genn.) biotype B for oviposition on squash genotypes (Cucurbita pepo) and to observe the susceptibility of genotypes (Novita, Sandy, Caserta Cac Melhorada, Novita Plus, Samira, Bianca, AF-2858 and Caserta TS) to silverleaf symptoms. The Sandy genotype was the least attractive to whitefly, while Novita Plus, AF-2858 and Samira were the most attractive. The Caserta Cac Melhorada genotype was the least preferred for oviposition. The Sandy and AF-2858 genotypes were the most productive, with the highest mean of fruits produced. The lowest silverleaf symptoms index was observed for the Sandy and Caserta Cac Melhorada genotypes.