Ovicidal Activity Trials, 1990

Treatments were applied to cotton grown in small plots at Stoneville, Miss. The test was applied 16 Jul using a high-clearance sprayer calibrated to deliver 6 gal/acre at 5 mph and 40 psi using 2, TX8 nozzles/row. Plot size was 30 ft × 4 rows arranged in a randomized complete block with 4 replicates/treatment. TB eggs were obtained from a culture maintained at the Southern Field Crop Insect Management Laboratory, USDA-ARS, Stoneville. All eggs used were laid the previous night on tulle cloth material. Eggs were not washed or subjected to chemical treatments before use and were easily removed by crumpling the material. Eggs were exposed to insecticides in 2 ways. First, eggs to be treated in the field were placed on the upper surface of the last 3—4 expanded leaves in the terminal of 4 plants in each replication by brushing a weak solution of xanthan gum and water on the leaves and sprinkling eggs on the surface. Plots were sprayed 30 min after application of the eggs. Eggs sprayed on the plant remained in the field for 2 h after treatment and were then taken to the laboratory to determine mortality. Second, treated leaves (4 from each replication) were collected at 24, 48, and 72 h after spraying in the field and taken to the laboratory where eggs were placed on them and mortality was determined over time. Eggs were sprinkled on each leaf in the field and in the laboratory in an effort to get at least 10 eggs/leaf. The number of viable eggs was counted on each leaf in the laboratory 24 h after being sprayed in the field or placed on sprayed leaves in the laboratory. The number of eggs/leaf averaged 15.0 ± 5.5 (S.D.). Leaves from all treatments were held in Petri dishes on water-moistened filter paper at 82°F. The number of unhatched eggs was determined at 72 and 96 h after eggs were applied. Eggs were considered dead when black and shriveled. Cumulative egg mortality 96 h after collection or treatment is reported. On 17 Jul, after the 24 h treated leaves were collected and prior to collection of 48 h treated leaves, 0.5 inch of rain was recorded.