Ovicide, Larvicide Trials, 1988

Abstract

A small-plot field study was conducted in a commercial field near Taft, Tex., to measure the efficacy of 5 treatments against eggs and freshly hatched larvae of tobacco budworm. Treatment efficacy was evaluated on eggs 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 7 Mar on 38-inch rows. Fresh eggs (24 h old) were placed on 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 22 Jun, 30 min after placement of eggs on leaves, with a CO2-pressurized (40 psi) backpack sprayer calibrated to deliver 4.4 gal total spray/acre through 2 size 3X hollow-cone nozzles/row. Based on visual examination, the coverage of leaves and eggs with treatment sprays was optimal. At 6 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. Each treatment was replicated 3 times in a randomized complete block. A replicate consisted of 2 leaves and 18-22 eggs, depending on the number of eggs lost in the field.