Insect pests and crop damage in soybeans

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Abstract
A survey and several field trials in the Auckland and Waikato areas from 1980 to 1982 found that the green looper caterpillar Chrysodeixis eriosoma (Doubleday) was the most common insect pest of soybeans. Insecticide trials showed that although C. eriosoma produced up to 15% defoliation this did not significantly reduce seed yields. Mechanical defoliation and cage experiments confirmed the ability of soybeans to fully compensate for up to 17% defoliation and identified the seed enlargement stage as the most susceptible for yield reduction. Estimates of economic injury levels from mechanical and natural defoliation indicated that C. eriosoma populations reached approximately half the density required to cause damage. Heliothis armigera conferta (Walker) occurred at low densities and damaged 5% of the pods but did not affect seed yield. The green vegetable bug Nezara viridula (L.) was not an important pest.