Studies on Corn Earworm Control in the Everglades

Abstract

The corn earworm, Heliothis zea (Boddie), is the most damaging insect that attacks sweet corn in Florida. This is especially true as most of the corn is sold as fresh corn under the grade of U. S. Fancy. Among other requirements, a U. S. Fancy ear must show no evidence whatever of corn earworm attack to the ear itself or even within the silk channel. No vegetable pest requires a more intensive spray program than that necessary to control this pest. Everglades growers spray or dust at least every other day from the time the first silks appear within a planting, until all the silks are dry. Where large acreages of corn are involved, the same sprayer or duster may be operated 24 hours a day. The author's primary objective in corn earworm control studies on sweet corn is to find ways to reduce the number of necessary insecticide applications, and, at the same time, maintain a high degree of corn earworm control. To date the fulfillment of this objective has not been accomplished. Spray applications were made with a high-clearance, self-propelled sprayer built at the Everglades Experiment Station 2. A Myers jumbo nozzle fitted with a No. 3 disc was used on each side of the sweet corn row. The nozzles were at approximately the same height as the silks, and at a right angle to the stalks. The spraying pressure was 200 pounds per square inch. For all trials, Golden Security variety of sweet corn was planted in rows that were three feet apart and thinned to give a 12-inch spacing within the row. Budworm and disease control was accomplished with DDTparzate sprays until the time of silking. Experimental insecticide applications were begun the day after the first silks appeared and continued until all silks were dry. In each experiment a randomized complete block design employing four replications was used. A 100-ear sample was examined in each plot to determine the percentage of ears that were free of earworm injury. Before analysis of variance was conducted, these percentages were transformed to angles (arc sin V % ).