Vegetable Oil Sprays of Larvin UCLF-5; Activity Against Tobacco Budworms Under Rainy Conditions, 1987

Abstract

Abstract A small-plot field study was conducted to evaluate different spray formulations of Larvin UCLF-5 for efficacy against tobacco budworm larvae in cotton. Four treatments and an untreated check were compared in 1-row × 6.7-ft plots of cotton planted 16 Apr on 38-inch rows. Treatments and the untreated check were replicated 3 times in a randomized complete block design. All plots were artificially infested twice with neonatal tobacco budworm larvae (laboratory colony maintained at the USDA Field Crop Insect Management Laboratory at Stoneville, Miss.). The first release of larvae was made 2 days before application of treatments (6 Jul), and the second release was made 1 day before application of treatments (7 Jul). Using a camel's hair brush, larvae were placed in shootterminals of randomly chosen plants in each plot (60 larvae/plot/release). On 8 Jul, treatments were applied to plots by using a modified CO2-pressurized backpack sprayer equipped with a controUed-droplet atomizer (Micro Max/DR4; Micron, Houston, Tex.) operating at 2,000 rpm. The atomizer was powered by a 12 V battery. The flow rate was regulated with a size 4916-16 regulator orifice plate (Spraying Systems, Wheaton, 111.) at 25 psi, which produced a finished spray volume of 1.3 gal/acre. The atomizer was held 10 inches above the row. At the time of treatment, the wind was 5-11 mph from SE (row direction was E to W), RH was 61%, and ambient temperature was 81°F. To prevent cross contamination of treatments from spray drift, 4 untreated buffer rows of cotton were planted between each plot, and a 4- × 3-ft plastic shield was carried next to the atomizer during treatment application (the shield was held 4 ft NW from the atomizer). Thirty-five min after application, a brief, hard rainfall of about 0.3 inches occurred at the test site. Treatment efficacy was evaluted 7 days after the application by inspecting 40 squares and 40 bolls/plot for budworm feeding. Numbers of larvae found in squares and bolls also were recorded.