Control of Lepidopteran Pests on Cabbage with Emamectin Benzoate and Bacillus Thuringiensis, 1997

Abstract

Abstract Two sets of 3 beds, 240 ft long on 6-ft centers and separated by a 15-ft drive, were prepared by fumigating with methyl bromide/chloropicrin 67/33% at a rate of 220 lbs/acre, fertilizing with a bottom mix of 800 lbs/acre 5-16-8 and a top mix of 210 lbs/acre of 19-0-19, and covering with a black polyethylene mulch. The center row in each set of 3 was planted 20 Nov 1996 with collard seedlings var ‘Georgia’ seeded 15 Oct 96 to provide inoculum of the target pests. Greenhouse-grown seedlings planted in flats on 10 Dec 1996 were transplanted in single rows on 29 Jan 1997 at 18-inch spacing and watered by a semiclosed irrigation system. An additional 46 lbs/acre of N and K was injected into the beds 30 days after transplanting and plants were sprayed with Bravo 720 at 1.5 pt/acre after transplanting for disease control. Each row of cabbage was considered one of 4 replicates and divided into 5 plots 34 ft long 5; to which treatments were randomly assigned in a RCB design. Sixty plants per row were checked for the presence of target pests on 13 Mar and treatments initiated after an average of 0.48 DBM larva per plant was observed. All treatments were sprayed weekly beginning 17 Mar for 5 weeks at a rate of 32 gpa , using a high-clearance sprayer at 200 psi of pressure and 3 yellow hollow cone AlbuzTM ceramic nozzles per row. Weekly evaluations 3 to 5 days after application on 12 randomly selected plants per plot consisted of counts of live DBM, CSW, CL larvae and a damage rating on 5 upper wrapper leaves and 3 J outer leaves of the head. Damage was rated as 0 = none, 1 = minor feeding (0-1 %) on wrapper leaves, 2 = 2-5% wrapper leaf surface, no head damage, 3 = 6-10% wrapper leaf area consumed with minor feeding on head, 4=11-30% wrapper leaf area consumed with moderate feeding on head, 5 = >30% wrapper leaf area eaten, considerable feeding and numerous feeding scares on head. At harvest the 15 largest heads per treatment were selected and graded for marketability based on amount of insect damage. The “Fancy” category had no insect damage to the head when harvested, whereas “standard” heads were damaged but could be salvaged for market by peeling the damaged outer leaves. The weight of the remaining “Standard” heads was added to the weight of the “Fancy” heads to obtain an estimate of marketable weight. A category of culls consisted of heads that were not salvageable due to extensive ; insect damage.