Impact of Insecticides on Lepidopterous Larvae and Leafminers on Tomatoes, 1986

Abstract

Abstract Seedlings were transplanted in a sandy loam type soil on 30 Jun at the University of California's South Coast Field Station in Santa Ana, Calif. Experimental plots were 4 rows wide (5-ft centers) by 50 ft long and separated by a 5-ft buffer. The tomato transplants were sprinkle irrigated for 1 wk and drip irrigated thereafter (water pH 7.2-7.5). Treatments were replicated 4 times in a randomized complete block design. Weekly applications were initiated at first fruiting. In the combination treatment, including RH 7988, Javelin, and Abamectin, as well as in the individual treatment, RN 7988 was only sprayed once (31 Jul) as aphid populations did not reach significant levels. In the same combination treatment, Abamectin and Javelin also were sprayed only once (31 Jul) because the leafminer population was low and plant samples suggested (incorrectly) that beet armyworm levels were low. Application dates were 31 Jul; 7, 14, 21, and 28 Aug; and 5, 11, 18, and 26 Sep. A tractor-mounted boom sprayer with 4-6 nozzles per row (as plant height and density increased) incorporated D-3 orifice disks, #23-25 cores, and 50 mesh screens. Operating pressure was 100 psi delivering 100 gal/acre. Spreader sticker (Leaf Act 80) was included for some treatments at 0.04%. Leafminer populations were evaluated by weekly counts of leafminer prepupae and pupae in four 9- by 11-inch trays/replicate from 13 Aug through 10 Sep, inclusive. On 2 and 3 Oct, 200 mature green to ripe fruit were harvested from the center 2 rows of each replicate (800 per treatment) and examined for internal damage (primarily H. zea) and external damage (primarily S. exigua and K. lycopersicon).