EVALUATION OF INSECTICIDES FOR MANAGEMENT OF A LOOPER COMPLEX AND A VELVETBEAN CATERPILLAR - GREEN CLOVERWORM COMPLEX ON SOYBEAN, 2002B

Abstract

Eight insecticides were evaluated to determine rate effects on Soybean looper (SL), Cabbage looper (CL), Green cloverworm (GCW) and Velvetbean caterpillar (VBC) on soybean. Pre-treatment insect counts revealed that larvae of each species were mainly in midto late instars on day 1 prior to application of the insecticides. Looper infestation consisted of 89% SL and 11% CL at the time the insecticides were applied. Because current identification of the larvae in the field is difficult, especially very small larvae, the number of loopers in samples was combined and reported as a looper complex (SL/CL). This same procedure was used to record the GCW and VBC (GCW/VBC) infestations, both species being about equally susceptible to many insecticides. Plots were located at the Mississippi State University Plant Science Research Farm, Mississippi State, MS. Soybeans were planted on May 29, 2002 in 38-inch rows, using the conventional planting system for soybean in the area. Treatment plots were four rows, 35 ft long, arranged in a randomized complete block design with four replications and a 8-ft alley between replications. Insecticide treatments were applied 8 Aug, using a backpack CO2 sprayer, equipped with eight CONEJET T 3X nozzles, 16 inch apart (2 nozzles per row), delivering 10 gpa at 40 psi, with water as a carrier for the insecticide. Soybeans were in the R5 stage. The environmental conditions at application were 68°F , 100% Rh, with sunshine and wind speed of less than 1 mph. Ground cloth samples were taken from the two middle rows of each plot on days 2 and 7 after spray application. Mean number of larvae in each complex was calculated for each date. Data were analyzed using SAS proc ANOVA, and means were separated using Fisher's least significant differences (LSD).