ARS | Publication request: FUNGUS-INDUCED BIOCHEMICAL CHANGES IN PEANUT PLANTS AND THEIR EFFECT ON DEVELOPMENT OF BEET ARMYWORM, SPODOPTERA EXIGUA HUBNER (LEPIDOPTERA: NOCTUIDAE), LARVAE

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 15, 2002
Publication Date: February 20, 2003
Citation: Cardoza, Y.J., Lait, C.G., Schmelz, E.A., Huang, J., Tumlinson III, J.H. 2003. Fungus-induced biochemical changes in peanut plants and their effect on development of beet armyworm, Spodoptera exigua Hubner (Lepidoptera: Noctuidae) larvae. 32(1):221-228. (lepidoptera: noctuidae), larvae. Environmental Entomology.

Interpretive Summary: When given a choice between leaves of peanut plants infected with white mold fungus and those of healthy plants, beet armyworms prefer to feed on the leaves of the infected plants. Scientists at the Center for Medical, Agricultural and Veterinary Entomology, USDA, ARS, Gainesville, FL, have discovered that beet armyworm caterpillars allowed to feed on fungus infected plants had higher survival rates and were healthier than those that fed on healthy plants. They also found that leaves of infected plants had higher levels of sugars and lower amounts of substances that deter caterpillar feeding than healthy plants. These results indicate that diseased plants are less capable of defending against insect pest attack than healthy plants. This type of information will be important in developing methods to prevent, manage and control crop pests.

Technical Abstract: In choice tests, beet armyworm (BAW), Spodoptera 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 3rd 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 to 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.