Positive association between thrips and spider mites in seedling cotton.

摘要

In cotton fields in Texas, spider mites are sporadic pests, whereas thrips are considered as major pests on early stages (before the fourth true leaf stage). Thrips are also important predators of spider mite eggs. In the present study, we tested the hypothesis that the presence of spider mites on seedling cotton may increase the likelihood of the occurrence of thrips. Based on a greenhouse experiment, it was confirmed that seedling cotton was a suitable host for spider mites. Subsequently, we conducted a 2-year field experiment in which we studied the likelihood of thrips infestation in cotton plants with/without experimental spider mite infestations. Spider mites established better in 2011 (dry and hot season) than in 2010 (rainy and cooler season), and there was a positive association between spider mites on cotton plants and natural thrips infestation. Thus, we showed that the probability of thrips infestation strongly increased with the presence of spider mites. To confirm the proposed hypothesis on a larger scale, a second field experiment was performed, in which one half of a field was infested with spider mites. Weekly sampling of thrips and spider mites showed a two-fold increase of thrips immatures on plots previously infested with spider mites. The results obtained in the present study emphasize the importance of incorporating spider mite population dynamics into risk assessments of thrips infestation in seedling cotton fields in Texas and elsewhere.