Population Development of Meloidogyne incognita on Soybean Defoliated by Pseudoplusia includens

Greenhouse studies examined population densities of Meloidogyne incognita race 4 on soybean (Glycine max 'Davis') defoliated by larvae of soybean looper (Pseudoplusia indudens (Walker)). Plants were defoliated over a 2-week period beginning 5 weeks after seedlings were transplanted. Four groups of plants were infested with nematodes (5,000 eggs/pot) at 2-week intervals to allow harvesting of plants at 0, 2, 4, and 6 weeks postdefoliation (WPD). Plants in each group were harvested 4 weeks after nematode infestation. Root and nodule weights of defoliated plants were suppressed at 0 WPD, but differences were not detectable at 2, 4, and 6 WPD. Population densities of M. incognita were similar on defoliated and control plants at 0 WPD but were greater on defoliated plants at 4 and 6 WPD. Percentage hatching of eggs produced on the latter plants also was higher. Effects of insect-induced defoliation on development of M. incognita remained detectable even after soybean plant growth apparently returned to normal.