Susceptibility Of Upland Cotton Cultivars To Bemisia Tabaci Biotype B (Homoptera : Aleyrodidae) In Relation To Leaf Age And Trichome Density

The relationships between leaf trichome densities, leaf age, and sweetpotato whitefly, Bemisia tabaci (Gennadius) biotype B, infestations of 13 upland cotton, Gossypium hirsutum L., cultivars were investigated in 1990 and 2000. Stoneville 474 supported higher numbers of B. tabaci biotype B eggs, nymphs and adults, and also had higher numbers of stellate trichomes on abaxial leaf surfaces compared with other cotton cultivars. Siokra L-23. in general, had fewer stellate trichomes and also fewer whiteflies. However, the positive trichome-whitefly density relationships were affected by the ages of leaves from different main stern cotton nodes. The youngest leaves on main stern node I below the terminal for all cultivars had higher numbers of stellate trichomes but fewer whiteflies compared with older leaves.