Slugs became a significant problem in soybean, Glycine max (L.) Merrill, in
the eastern USA cornbelt as growers adopted conservation tillage productio
n practices. Little information is known about the consequences from slug i
njury on soybean growth and yield. This study examined the effects of moder
ate levels of simulated slug injury, i.e., stand loss and defoliation to th
e unifoliate and Ist trifoliate leaflets, to the crop. Soybean stands were
established at levels at and above those requiring replanting, and defoliat
ion was done by removing 50% of the unifoliate and Ist 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% defo
liation of the unifoliate leaflet having a much lesser impact. There was li
ttle effect from injury to the Ist trifoliate. Results suggest that growers
should be most concerned when slug injury causes reduced stands and from d
efoliation to the unifoliate leaflet. Early planting that allows for maximu
m growth of the plant before slugs become active in later spring would lowe
r the potential for economic losses. (C) 2000 Elsevier Science Ltd. All rig
hts reserved.