INFLUENCE OF LEAF PUBESCENCE ON OVIPOSITIONAL PREFERENCE OF BEMISIA-ARGENTIFOLII (HOMOPTERA, ALEYRODIDAE) ON SOYBEAN

The influence of pubescence on oviposition site selection by Bemisia a rgentifolii Bellows & Perring [also known as the B strain of sweetpota to whitefly Bemisia tabaci (Gennadius)] was studied in greenhouse and laboratory bioassays using soybean, Glycine max L., isolines varying f or foliar pubescence. In choice tests, whiteflies laid significantly m ore eggs on the hirsute and pubescent isolines than on the glabrous is oline. In no-choice tests, the within-plant distribution of eggs laid on the 3 isolines differed and was related to trichome density. On gla brous soybean more eggs were laid on tile 2 oldest and 2 youngest leav es. On the 2 hairy isolines, more eggs were laid on the 3 oldest leave s and fewer eggs were laid on the younger leaves, which had the highes t densities of trichomes. When whiteflies were confined in petri dish- clip cages attached to plants with a choice between 2 leaflets, either from 2 different isolines or within a single isoline, no preference f or pubescent over glabrous soybean was seen nor did removal of hairs b y shaving affect ovipositional preference. However. significantly more eggs were laid on hirsute soybean than on glabrous soybean in between -isoline choice tests. In addition, shaved hirsute leaflets were less preferred for oviposition than hirsute leaflets in within-isoline choi ce tests. It is likely that the partial resistance of glabrous soybean observed in the field is caused, in part, by reduced ovipositional pr eference related to lack of foliar pubescence. However, die effect of trichomes on ovipositional preference is less pronounced when whitefli es are closely confined with host plants.