Evaluation of Insecticides for the Control of Lepidopteran Larvae in Sweet Corn in Virginia, 2014 *

The objective of this experiment was to assess the efficacy of insecticides for the control of lepidopteran pests of sweet corn in eastern Virginia. The experiment consisted of 9 treatments arranged in an RCB design with four replicates. “Merit” sweet corn was planted on 17 June 2014 at the Virginia Tech Eastern Shore Agricultural Research and Extension Center in Painter, VA. Plots were 2 rows wide and 20 ft (6.1 m) long with no guard rows. Rows were planted on a 3 ft row center (0.9 m) in a 4 tier field design, 6 ft (1.8 m) alleys between tiers. Insecticide treatments were applied at 80% tasselling on 4 August and were repeated on 6, 8, 11, 13, 15, and 18 August (7 total applications). Each spray was applied at 38 gpa with a 1-nozzle boom equipped with a D3 spray tip and 45 core and powered by a CO ₂ backpack sprayer at 40 psi. On 19 August, a sample of 25 ears was collected from each plot, shucked and examined for presence of lepidopteran larvae and feeding damage. The species and number of lepidopteran larvae was recorded as well as the number of undamaged, tip damaged, and severely damaged ears. All data were analyzed using ANOVA. Proportion data were arcsine square root transformed prior to analysis. Means were separated using Fisher’s LSD at the 0.05 level of significance.

Lepidopteran pest pressure was heavy with 88% total damaged ears in the untreated control and 28 live larvae per 25 ears. The lepidopteran pest complex was primarily comprised of CEW (98%). All treatments had significantly fewer % unmarketable (severely damaged) ears than the untreated control except Warrior II ZT rotated with Blackhawk, and Fastac. Besiege rotated with Warrior II ZT had the lowest overall damage of any of the insecticide treatments. All treatments had significantly fewer % tip damaged-only ears than the untreated check except both rates of cyclaniliprole and Belt followed by Warrior II ZT. All treatments; however, had significantly fewer % total damaged ears and mean no. of CEW larvae in ears than the untreated check. Besiege followed by Warrior II had the fewest total damaged ears and number of live larvae among all insecticide treatments. No signs of phytotoxicity were observed.

Author notes