Leaf temperature affects resistance to the banks grass mite (Acari : Tetranychidae) on drought-resistant grain sorghum

Field and greenhouse experiments were performed to screen sorghum lines for antibiosis to the Banks grass mite, Oligonychus pratensis (Banks), and to determine if a relationship exists between different types of drought resistance and antibiosis to the Banks grass mite. We also tested the hypothesis that Banks grass mite development and population growth during drought stress in slower on drought-resistant than on drought-susceptible sorghum lines because lower leaf temperatures are usually maintained on the former. Banks grass mite development time in degree days, fecundity, and leaf area coverage were measured on sorghum lines previously classified as either preflowering drought-resistant, postflowering drought-resistant, overall drought-resistant, or drought-susceptible. Pre- and postflowering, drought-resistant lines were the most resistant to Banks grass mite population growth under dryland conditions with moderate postflowering drought stress. Banks grass mite development time depended on leaf temperature and was also different among lines, suggesting that leaf temperatures varied among lines. Likewise, fecundity was affected by temperature, but after the temperature differences were taken into account, fecundity was not significantly different among lines.