Drought Stress and Genotype Interactions Influence Oviposition of Spider Mite on Cotton

It is known that spider mite invasions are favored by drought conditions, and high temperatures reduce development time and increase egg laying rate. However, direct influence of plant drought stress on spider mites is not well understood. We present results from a series of experiments that examine the influence of cotton genotype in cotyledon stage and water level on oviposition and female behavior under constant temperatures. Based on experimental infestation of individual cotyledon plants (no-choice) from five genotypes and subsequent counting of spider mite oviposition during 48 hours, we observed that spider mite oviposition on a thrips resistant genotype was low (i.e., reduced oviposition) but only when well watered. Conversely, spider mite oviposition on a drought resistant genotype was lowest when plants were grown under drought stress. Based on choice tests, results from no-choice tests were corroborated as we showed clear correlation between changes in drought stress with changes in the oviposition preference by spider mite females. In another study, we monitored spider mite population development and leaf temperatures during 10 days on the five genotypes and showed that the drought resistant line was the only genotype to not show an increase of oviposition and leaf temperature under drought stress. Finally, we found no significant difference in the hatching rate of the eggs on different genotypes or under different drought-regimes. The results from this study will be used to discuss drought resistance and its association with pest susceptibility.