Wh Itefringed Beetle Ld50 Studies, 1976

Adult whitefringed beetles were field collected and held in groups of 100 in screen cages. Fresh soybean leaves were supplied each day as a food source. Blotting paper was fitted and taped to the floor of the cages as an oviposition site. This paper was removed daily, sections containing egg masses clipped off, and egg masses incubated. Newly enclosed larvae were used in the ensuing bioassay. Fine, sandy loam soil was collected from an insecticide-free area on the Auburn University Agronomy Farm, throughly mixed, and screened to remove rocks and debris. The insecticides were incorporated into the soil by weighing the insecticides, measuring the soil volumetrically mixing the two for 5 minutes in a 3-cu-ft electrically powered cement mixer. The cement mixer was carefully cleaned after each batch. Rates selected for testing were calculated to approximate the concentration in the top 3 inch of soil as it would occur under field conditions. Preliminary tests were conducted to determine insecticidal rates that would produce greater than 5% but less than 95% mortality for each insecticide used. Four rates from within this "effective dosage" range were then selected for the final test for each insecticide. Insecticides used were field grade granular formulations (Table 1). Treated soils were placed in 148-ml containers to a depth of ca 76 mm (3 inch). Ten newly enclosed larvae were placed in each container. All treatments were replicated four times and untreated checks were provided in each test. Insects were held in a rearing room maintained at 25°C and 60% RH throughout the experimental period. After 7 days, larval mortality was determined by recovering the larvae from the soil by flotation with MgSC>4 solution (400 g MgSO4L H2O). Data were corrected for natural mortality through the use of Abbot's formula and were then analyzed statistically by the Bliss log probit method.