Insecticidal Control of Fall Armyworm in Florida Sweet Corn, 1992

Abstract

Abstract Six raised beds on 6 ft centers prepared on 17 Aug included a fertilizer bottom mix of 1000 lbs/acre of 5-16-8 and 800 lbs/acre of 19-0-19 placed in a central band at bedding. Beds were fumigated with 220 lbs/acre of methyl bromide injected every 5 inches across the bed width and sealed immediately with white-faced, black polyethylene. On 5 Oct, two seeds per hole of the cultivar ‘Florida Staysweet’ were planted in two rows 10 inches apart in the center of each bed and later thinned to one plant per space. Manzate 200 was applied weekly with a plot sprayer at 100 psi to prevent leaf blight and rust. Each of two sets of 3, 240 ft rows was divided into two blocks, 50 ft long, with 100 row ft between blocks. Each row was randomly assigned one of 2 treatments or a control water-treatment in a RCB design. Spray applications were made weekly over 8 weeks beginning 30 Oct using a CO2 pressurized backpack sprayer manufactured by Weed Systems, Inc., Gainesville FL. At an operating pressure of 40 psi, the first 5 applications were calibrated at a rate of 30 gpa and the last 3 at 45 gpa. The surfactant, APSA-80 (80% Alkyl Aryl Alkoxylate) was added at the rate of 0.3% to the Larvin application. Armyworm counts and damage ratings were made one day prior to the first treatment and weekly thereafter by examining the whorl and the next 2 adjacent leaves before tasseling and all ears thereafter. The following numerical ranking system was used for damage ratings: 0: no damage, 1: windowing to 10%, 2: 11-30%, 3: 31-40%, 4: 41-50%, and 5: greater than 50%. Larvae observed during field evaluations were recorded. Plots were harvested on 21 Dec and 7 Jan. All the mature ears were collected and counted and weighed. The number of damaged ears was noted and ears weighed.