Evaluation of the Pest Status of the Threecornered Alfalfa Hopper (Homoptera: Membracidae) on Soybean in Louisiana

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Abstract
Field tests were conducted in 1981 and 1982 to determine the feeding damage of three cornered alfalfa hopper, Spissistilus festinus (Say), on soybean, Glycine max (L.) Merrill, yield. Insecticides were applied in various early season/late season combinations in order to establish different S. Festinus population levels. Significant differences among treatments were found for early and late season S. festinus populations, levels of early and late season girdling, leaf area indices, stand density, and yield. Early season damage did not affect yield. Correlation analyses demonstrated a significant negative correlation for yield with late season populations and late season damage. Yield reductions ranging from 396.8 to 1,189.5 kg/ha were associated with late season populations ranging from 48 to 476.5 adults per 100 sweeps of a 38-cm diameter sweep net. These data contributed to the establishment of an economic threshold of 1 adult per sweep after the beginning of pod set for S. festinus on soybean in Louisiana.