EVALUATION OF INTREPID AND ENTRUST FOR CONTROL OF LEPIDOPTEROUS LARVAE ON FALL LETTUCE, 2003

Abstract

The objective of the study was to evaluate two new reduced-risk insecticides (Intrepid and Entrust) for control of Lepidopterous larvae on fall head lettuce under desert growing conditions. Lettuce was direct seeded on 5 Sep at the Yuma Valley Agricultural Center, Yuma, AZ into double row beds on 42-inch centers. Stand establishment was achieved using overhead sprinkler irrigation, with furrow irrigation used thereafter. Plots were two beds wide by 45-ft long and bordered by two untreated beds. Four replications of each treatment were arranged in a RCB design. Formulations and rates for each compound are provided in the tables. Sprays were applied on 25 Sep, 4, 14 and 22 Oct. The first and second applications were made with a CO2 operated boom sprayer at 60 psi and 13 gpa. A broadcast application was delivered through 2 nozzles (TX-12) per bed. The third application and fourth applications were made with a CO2 operated boom sprayer at 60 psi and 25 gpa. A directed spray (approximately 75% band, with rate adjusted for band) was delivered through three nozzles (TX-12) per bed. A spreader/sticker, Latron CS-7, was applied at 0.07% v/v with all treatments except for Success and Entrust. Evaluation of control was based on the number of live larvae per plant sampled from the two beds of each replicate. Five plants per plot were destructively sampled on 28 Sep, 2, 7, 11, 21, 27 and 30 Oct. The sample unit consisted of examination of whole plants for presence of small and large BAW and CL. For BAW, larvae were considered small if 5mm in length. For CL, larvae were considered small if 10 mm. Treatment means were analyzed using a 1-way ANOVA and means separated by a protected LSD (P ≤ 0.05).