Cotton treatment with methyl jasmonate at different growth stages reduces the population of sucking insect pests and marginally increases their associated predators

Abstract

AbstractMethyl jasmonate (MEJA), a volatile organic compound, can induce plant defenses, thereby contributing to repelling insect pests and attracting their natural enemies. In 2013 and 2014, the influence of three exogenous MEJA doses (0.88, 1.76, and 3.55 mM) under field conditions was investigated on the abundance of the cotton pests Thrips tabaci Lindeman (Thysanoptera: Thripidae), Empoasca decipiens Paoli (Hemiptera: Cicadellidae), and Aphis gossypii Glover (Hemiptera: Aphididae), as well as of the predators Coccinella septempunctata L. (Coleoptera: Coccinellidae), Aeolothrips intermedius Bagnall (Thysanoptera: Aeolothripidae), and Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae). The MEJA treatments were performed at three cotton plant growth stages: 6–8 true leaves‐early squaring, square bud, and boll forming. The abundances of A. gossypii, T. tabaci, and E. decipiens varied considerably among strata and growing seasons and between experimental years, but overall they were lower on MEJA‐treated cotton plants than on control plants. The population density of A. intermedius and C. septempunctata did not differ between MEJA‐treated and control plants, whereas the intermediate MEJA concentration had an attractive but inconsistent effect on C. carnea. Most of the insect pests and predators showed a preference for specific plant strata. The abundance of T. tabaci was higher in earlier plant growth stages, whereas A. gossypii and E. decipiens were more abundant in later growth stages. Our results demonstrate the deterrent effects of MEJA‐induced cotton plants on sucking pests and suggest that MEJA could be exploited as a non‐toxic pest management tool. Possible mechanisms underlying the effectiveness of MEJA‐mediated cotton plant responses to insect pests are discussed.