A small-plot field study was conducted in a commercial cotton field near Austwell, Tex., to evaluate efficacy of Karate (3 formulations), Baythroid, and Guthion for tobacco budworm and boll weevil control. 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 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. Heliothis spp. larvae (n = 50) were collected from the test plots and reared to adulthood for identification of species. Applications were made 17, 22, and 27 Jul. Twenty-five randomly selected squares or bolls/plot were inspected for the presence of tobacco budworm larvae and damage and boll weevil damage on 21, 26, and 29 Jul. Seed cotton was hand-harvested from a 6.8-ft section of row in each plot for yield analysis.
A caged-plant study was conducted in a commercial cotton field near St. Paul, Tex., to compare the effects of water and nonemulsified cottonseed oil on the efficacy of Asana XL, Karate, and Baythroid for boll weevil control. A cottonseed oil control (without insecticide) and an untreated control were included in the study to measure boll weevil mortality due to exposure to oil or natural causes. Boll weevils used in the study were collected from blooms in an untreated cotton field approximately 20 miles from the test site. Water treatments were applied to cotton 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. Oil treatments were applied to cotton with a modified CO2-pressurized backpack sprayer equipped with a controlled droplet atomizer operating at 2,000 revolutions/min. The atomizer produced a droplet size of 130 p.m in volume mean diam based on data from the supplier. The atomizer was powered by a 12 V battery. The flow rate was regulated with a size 4916-16 regulator orifice plate and a pressure of 25 psi. Based on ground speed, this produced a finished spray volume of 1.3 gal/acre. Water treatments were applied to 3-row by 50-ft plots. Oil treatments were applied to one-row by 50 ft plots. Twenty-five untreated buffer rows of cotton were planted between each plot to prevent cross contamination of treatments from spray drift. Adult boll weevils were caged 5-min after application. Cages were constructed of organdy cloth fastened at the top and bottom with Velcro strips. The caged plants were brought into the laboratory and inspected for the presence of live or dead and moribund boll weevils 48 h after infestation. A boll weevil was considered dead if it failed to move when its snout was squeezed with forceps. A boll weevil was considered moribund if it moved its legs only slightly when its snout was squeezed with forceps and if it was unable to walk on a flat surface without falling on its side. Numbers of dead and moribund boll weevils were combined as a measure of percentage of mortality. Each treatment was replicated 6 times in a completely randomized design. A replicate consisted of one plant infested with 10-12 boll weevils.
A small-plot field study was conducted in a commercial cotton field near Austwell, Tex., to measure the efficacy of 11 treatments against tobacco budworm and boll weevil. 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. Heliothis larvae (n = 50) were collected from the test plots and reared to adulthood for identification of species. Applications were made 13, 18, and 23 Jul. Twenty-five randomly selected squares or bolls were inspected from each plot for the presence of tobacco budworm larvae and damage and for boll weevil damage on 17, 22, and 27 Jul. Seed cotton was hand-harvested from a 6.8-ft section of row in each plot for yield analysis.
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.
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.
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