Navon, A., Department of Entomology, Bet Dagan 50-250, Israel
Melamed-Madjar, V., Department of Entomology, Bet Dagan 50-250, Israel
Zur, M., Department of Plant Introduction, ARO, The Volcani Center, Bet Dagan 50-250, Israel
Ben-Moshe, E., Department of Plant Introduction, ARO, The Volcani Center, Bet Dagan 50-250, Israel

Three pubescent cultivars of cotton Gossypium hirsutum: 'Texas-172', 'Pilose hybrid' and 'Texas-100', one glabrous cultivar 'Sicot-2', and the commercial variety 'Acala SJ-2' were bioassayed in the laboratory and in the field against the lepidopterous pests, Spodoptera littoralis and Heliothis armigera, and against the tobacco whitefly, Bemisia tabaci. The non-gladular trichome density and size on both leaf sides in the field were determined and the nature of this pubescence described. The density and size of the pigment glands were recorded in 'Texas-172' and 'Acala SJ-2'. The weight gain and leaf feeding capacity of the two lepidopteran larvae on the pubescent cultivars was smaller than on the glabrous 'Sicot-2' or 'Acala SJ-2'. However, shaving the trichomes from the leaves of 'Texas-172' did not increase feeding of H. armigera and the larvae in the shaved leaf partially avoided the ingestion of the pigment glands. The reduced feeding may be the result of an antibiosis effect of the glands. Bemisia tabaci oviposition on the pubescent cultivars was significantly higher than on 'Sicot-2' and the commercial cotton variety. © 1991.