Ovicide, Larvicide Trials, 1988

Abstract

A small-plot field study was conducted in a commercial cotton field near Austwell, Tex., to measure the effects of 5 treatments on survival of eggs and freshly hatched larvae of the tobacco budworm. The eggs were obtained from a pyrethroid-susceptible strain of tobacco budworm (ICI laboratory colony maintained at the Texas A&M University Research and Extension Center at Corpus Christi). Treatments were compared in 5-row by 50-ft plots of cotton planted 28 Apr on 30-inch rows. Each treatment was replicated 3 times in a randomized complete block. Treatments were applied with a CO2 pressurized (38 psi) backpack sprayer calibrated to deliver 4.4 gal total spray/acre through 2 size 3X hollow-cone nozzles/row. Fresh eggs (24 h old) were attached manually to the upper surfaces of leaves (10-12 eggs/leaf) located near the shoot terminal of each of 6 flowering cotton plants/treatment with a camel’s hair brush moistened with distilled water. Treatments were applied to plants within 30-min of placement of eggs on 13 Jul. At 4 h after application, all leaves that contained eggs were collected and placed individually into covered plastic Petri dishes containing filter paper moistened with distilled water. The eggs were held for 72 h, then inspected for unhatched eggs and dead or live larvae. A replicate consisted of 2 leaves and 18-22 eggs, depending on the number of eggs lost in the field.