Control of Heliothis Spp. Eggs and Neonate Larvae, 1988

Insecticide treatments were applied 21 Jul in a small-plot study conducted on the Northeast Research Station near St. Joseph, La., to evaluate the efficacy of selected pyrethroids on Heliothis spp. eggs and their residual toxicity on newly hatched larvae. This test was carried out in a field of cotton planted 24 May in a silt loam soil. The field had not been treated with insecticides prior to the test. All treatments were applied using a Kubota utility tractor equipped with a compressed-air system calibrated to deliver 5 gal total spray/acre through Teejet X-6 hollow-cone nozzles (2/row) at 35 psi. Plots consisted of 4 rows (40-inch spacing) by 50 ft arranged in a randomized complete block design and replicated 4 times. Freshly laid white Heliothis spp. eggs (10/plot) were randomly collected from each plot 4 h after treatment. The eggs were placed on artificial rearing media, transported to the laboratory, and held at room temperature (80°F). Mortality to eggs and larvae was determined 96 h after removal from the field. The survivors of the egg cohort in the untreated control were reared to adults and identified to be 93% tobacco budworm. Eggs were considered dead if they did not hatch. Larval mortality was recorded if the insect was unable to move after being prodded. For the duration of the study there was no rainfall recorded and the relative humidity was low. The cotton plants were approximately 40 inches tall and averaged 10-15 squares/plant.