Sweet Corn Insecticide Efficacy Trial, 2014 *

The objective of the study was to evaluate the efficacy of insecticidal materials for control of corn earworm (CEW) on sweet corn under desert growing conditions during the spring season. Sweet corn, “Xtra-Tender 1278” was direct seeded on 21 March 2014 at the University of California Desert Research and Extension Center, Holtville, CA, into single row beds on 40-inch centers. Stand establishment and crop maintenance was achieved using furrow irrigation. Plots were two beds in width (6.67 ft) by 50 ft in length. Five replications of each treatment were arranged in an RCB design. Formulations and rates for each compound are provided in Table 1 along with the adjuvants used; RNA Activator 85 (RNA, San Joaquin, CA) or Hasten-modified vegetable oil (Wilbur-Ellis Company, San Francisco, CA). The insecticide applications were made on dates indicated in Table 1 , with a 6-nozzle, 2-bed boom, on a handheld CO ₂ propelled sprayer, with 3 Conjet TXVS-4 nozzles per bed spaced 15 inches apart; outer 2 nozzles on 15 inch drops facing the plant angled 135° down from vertical delivering 17.9 gpa at 30 psi. Evaluation of insecticide efficacy against CEW was based on the number of live larvae and numbers of CEW damaged ears per 20 randomly selected corn ears per plot and on the average length (cm) of CEW feeding damage per ear (the length of damage from the ear tip) on 16 June 2014. Data sets were analyzed using two-way analysis of variance and means separated by a protected LSD ( P  < 0.05). Arcsine transformation (ARSIN(SQRT(X))) was also used for percentage data shown in Table 2 .

The CEW pressure was high for the spring sweet corn season. None of the insecticide treatments had significantly fewer CEW larvae than the untreated check, but all of the insecticide treatments had fewer CEW damaged ears than the untreated check ( Table 2 ). All of the insecticide treatments had fewer total cm of CEW damage to the sweet corn ear tips compared to the untreated check. The percentage of sweet corn ears damaged by CEW in the untreated check was significantly greater than the percentages of CEW damaged ears in any of the insecticide treatments. The percentages of CEW damage ears for all of the insecticide treatments were above a level acceptable for commercial production. No phytotoxicity symptoms were observed following any of the insecticide treatments.

Author notes