Nodulation, nitrogen fixation, and organ dry weight of soybean infested with southern corn rootworm (Coleoptera: Chrysomelidae) larvae

Nitrogen fixation, nodulation, and organ dry weights of soybean infested with the larvae of the southern corn rootworm, Diabrotica undecimpunctata howardi Barber, were estimated under controlled conditions. Larval southern corn rootworm reduced the nitrogen-fixing activity of mid-vegetative and early reproductive soybean, Glycine max Merrill. Soybean of both stages responded to the infestation and subsequent injury by increasing nodulation and organ dry weights of below-ground tissues relative to above-ground tissues. Infestation increased the dry weight of small nodules on vegetative plants and caused a 78.6% increased in the total number of nodules on R5 plants. Leaf area as well as leaf and stem dry weight was reduced in vegetative plants by infestation.