Establishment of Spider Mites on Cotton Plants In a Semi-Arid Environment

Spider mites are commonly reported pests on cotton in China; Arkansas; or Australia, and they are known to infest all development stages of the plant. However in the Southern High Plains (SHP) of Texas, spider mites are only considered occasional pests associated with drought stress, and they have only been reported as pests on late season cotton. However, under greenhouse conditions in the SHP, spider mites frequently attack cotton in cotyledon stage. In the SHP, wheat is harvested around May, which is when cotton is in the cotyledon stage, and wheat can host considerable spider mite populations, so theoretically spider mites could disperse from maturing wheat into developing cotton. However, this does not seem to occur, and our overall goal with this study is to explain why. Here, we report spider mite establishment in three environments: 1) field plots 2) greenhouse and 3) rain shelter. In each environment, plastic bottles were placed around cotton plants in cotyledon stage, while other plants were uncovered, and all cotton plants were infested with spider mites. The results showed that spider mites are favored by high temperature and low relative humidity, but the spider mite development was highest on a drought susceptible compared to a drought tolerant genotype. Moreover higher infestation rate in rain shelter and greenhouse suggests that factors such as wind and/or presence of thrips contribute to regulate spider mites population under field conditions.