Control of Cabbage Looper and Imported Cabbageworm on Collards with Encapsulated Virus Formulations, 1987

Abstract

Abstract 'Vates' collards were direct seeded in 4 row plots 20 ft long on 24 Jul. Plants were spaced 2 inches apart in the row with 36 inches between rows. The treatments were arranged in a randomized complete block design with 4 replications and each sprayed row buffered by a guard row. The soil was a Norfolk A loamy sand. All spray treatments were mixed in 0.5 liter of water to which 0.01% of a liquid detergent was added as a spreader and applied with a trombonetype garden sprayer calibrated to deliver 30 gal/acre. The Autographa californica nuclear polyhedrosis viruses (AcNPV) and Trichoplusia ni granulosis virus (TnGV) were encapsulated with or without dyes to determine the effectiveness of the encapsulation of dyes with the viruses for protection from the ultraviolet (UV) portion of sunlight. All of the virus treated rows also had Artogeia rapae granulosis virus applied so that damage primarily caused by cabbage looper could be assessed, since the NPVs do not infect the imported cabbageworm. All rows were treated with their respective applications on 25 and 31 Aug and 8 Sep. On each application date 20 second-instar T. ni larvae were released on each of the test rows. On 17 Sep the foliage injury ratings and insect counts were taken. Foliage injury ratings ranged from 1 to 5 and were indexed as follows: 1, 0-3% damage—odd holes on leaves; 2, 4-10% damage—few leaves with holes; 3, 11-25% damage—moderate number of leaves with holes; 4, 26-50% damage—most leaves with holes; and 5, 51-100% damage—crown damage and/or all leaves with holes.