Simulation of moderate levels of slug injury to soybean

Abstract

Slugs became a significant problem in soybean, Glycine max (L.) Merrill, in the eastern USA cornbelt as growers adopted conservation tillage production practices. Little information is known about the consequences from slug injury on soybean growth and yield. This study examined the effects of moderate levels of simulated slug injury, i.e., stand loss and defoliation to the unifoliate and 1st trifoliate leaflets, to the crop. Soybean stands were established at levels at and above those requiring replanting, and defoliation was done by removing 50% of the unifoliate and 1st trifoliate leaflets. Plant growth measurements were taken during the summer and yields recorded. The greatest impact on yield was from reduced plant stands, with 50% defoliation of the unifoliate leaflet having a much lesser impact. There was little effect from injury to the 1st trifoliate. Results suggest that growers should be most concerned when slug injury causes reduced stands and from defoliation to the unifoliate leaflet. Early planting that allows for maximum growth of the plant before slugs become active in later spring would lower the potential for economic losses.