Fungus-induced biochemical changes in peanut plants and their effect on development of beet armyworm, Spodoptera exigua Hübner (Lepidoptera: Noctuidae) larvae

Abstract

In choice tests, beet armyworm (BAW), Spodaptera exigua, larvae feed preferentially on leaves from peanut plants, Arachis hypogaea L., previously infected by the white mold fungus, Sclerotium rolfsii Saccodes (mitosporic fungi) (Cardoza et al. 2002). In this study we determined that third instar BAW caterpillars allowed to feed on S. rolfsii-infected plants had significantly higher survival, produced significantly heavier pupae, and had shorter time to pupation than those allowed to feed on healthy plants. Leaf tissue from white mold infected peanut plants contained similar levels of soluble and insoluble protein, but significantly higher levels of soluble sugars. In addition, white mold-infected plants had significantly lower starch content and total soluble phenolics compared with leaves from healthy plants. Levels of jasmonic acid were similar in plants attacked by either the fungus or BAW, but were significantly higher in plants that were infected by the fungus and then fed on by BAW. Salicylic acid (SA) levels in fungus-infected plants were not significantly different from those of control plants. However, levels of SA in plants damaged by BAW alone were significantly lower than those of plants under simultaneous attack by the fungus and BAW.