Impact of Insecticides on Lepidopterous Larvae and Leafminers on Tomatoes, 1989

Abstract

Abstract Seedlings were transplanted in a sandy loam type soil on 6 Jul at the University of California's South Coast Field Station in Santa Ana, California. Experimental plots were 4 rows wide (5-ft centers) by 40 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. Application dates included 15, 22, 29 Aug and 6, 12, 19, 26 Sep. A tractor-mounted boom sprayer with 4—6 nozzles/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 21 Aug through 25 Sep, inclusive. On 2 Oct, 200 mature-green to ripe fruit were harvested from the center 2 rows of each replicate (800/treatment) and examined for internal damage (primarily H. zea) and external damage (primarily S. exigua and K. lycopersicon). Leafminer populations were low throughout this test. Some insecticides increased leafminer density as compared to the control plots. Beet armyworm populations were moderate, tomato pinworm populations were low and tomato fruitworm populations were low. No phytotoxicity was observed in any treatment.