Submitted to: Journal of Entomological Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/4/2007
Publication Date: 1/10/2008
Citation: Lundgren, J.G., Riedell, W.E. 2008. Soybean Nitrogen Relations and root characteristics after Cerotoma trifurcata (Coleoptera:Chrysomelidae) larval feeding injury. Journal of Entomological Science. 43(1):107-116. Interpretive Summary: Subterranean insect life stages are difficult to study, but are potentially very damaging to crops. Bean leaf beetle is a pest of economic concern to soybean producers, but damage is only understood for the adult stage. The feeding behavior of subterranean larvae has never been described as it pertains to soybean production. Under greenhouse conditions, we showed that bean leaf beetle larvae de-nodulate soybean plants, and that soybeans respond to feeding by increasing the number of small nodules on their root system. Larval damage could have important implications for how soybeans produce their food under field conditions.
Technical Abstract: The hypothesis that larvae of Cerotoma trifurcata do not injure the roots of soybeans (Glycine max L.) was tested in the greenhouse. Pots containing individual plants were either not infested or infested at high (19 larvae per pot) or low (5 larvae) levels. After 3 wk, the plants were dissected and the fresh and dry weights of the roots and shoots were recorded. Also, the number of nodules, number of damaged nodules, and the area and volume of nodules were compared among the treatments. Nodules were the only root system organ visibly damaged by larval feeding. External nodule surfaces were scarred, and frequently the internal matrices of the nodules were completely excavated by the larvae. Significantly more nodules per plant were found in the infested treatments, and damaged nodules were significantly more abundant on plants in the high infestation compared with those in the low infestation treatment. Also, plants from the high infested treatment had significantly smaller nodules than the uninfested control, suggesting that the infested plants responded to larval damage by producing additional nodules. The implications for larval infestation to soybean production are discussed.