RECOGNITION OF BRASSICA-OLERACEA L RESISTANCE AGAINST THE SILVERLEAF WHITEFLY

Resistance of a Brassica oleracea germplasm collection (broccoli, Ital ica Group; cauliflower, Botrytis Group; and collard and kale, Acephala Group) to silverleaf whitefly (SLW; Bemisia argentifolii Bellows and Perring) infestation was evaluated using several measures of insect in festation (including adult vs. nymph counts) taken at plant growth sta ges ranging from seedling to mature plant. An initial study was conduc ted in an outdoor screen cage artificially infested with the SLW adult s; subsequent field trials relied on natural infestations. The glossy- leaved lines ('Broc3' broccoli, 'Green Glaze' collard, and LSC Glaze' collard) had low SLW infestations in cage and field tests. SLW adult c ounts were less variable than similar comparisons using nymphal counts , although adult and nymph counts were positively and significantly co rrelated at late plant stages, Based on this study, comparing relative SLW adult populations would be a preferred criterion for identifying B. oleracea resistance to this insect.