Field Evaluation of a Gypcheck-Folic Acid Formulation for Gypsy Moth Control, Maryland, 1985

Abstract

Abstract Folic acid was evaluated as a sunlight screen to promote efficacy of the gypsy moth nucleopolyhedrosis virus product, Gypchek, in low to moderate density gypsy moth populations in eastern Maryland. Woodlots were blocked by egg mass density and each woodlot within a block was randomly assigned one of three treatments; Gypchek + folic acid, Gypchek, and control (no spray). There were 5 replicates of each Gypchek treatment and 4 replicates of controls. One Gypchek treatment contained Gypchek, 5.1 g; 20% feed grade folic acid, 25.6 g; Rhoplex B60A per liter of finished spray, 20.5 ml; 8L inert ingredients (Abbott Laboratories) 250 ml; and water, 730 ml. The other Gypchek treatment contained the same less the folic acid. The control treatment was no spray. Gypchek was applied at 5 × 10u polyhedral inclusion bodies (PIB)/ha in 9.4 liter/ha. Aerial application commenced when the expansion of white oak foliage was ≥50% and ≥75% of the gypsy moth larvae were in the first and second stages. Application was by a 600 hp Grumman AgCat equipped with a standard boom and eight Micronair AU5000 atomizers calibrated to deliver a droplet VMD 125-200 u,m. Two applications of each treatment were made (4 and 8 May). Effective swath width was 23 m, airspeed was 184 km/h, and spray height was 10-20 m above the canopy for both applications. Evaluation was based on comparisons of pre- and posttreatment egg mass counts within 25 0.01-ha subplots established on a grid system within each treatment woodlot and on defoliation in each subplot estimated from low-altitude infrared photographs taken at the cessation of larval feeding. Defoliation was rated on a l-to-4 scale; 1, none; 2, low; 3, moderate; 4, high. Average defoliation was calculated from the weighted mean for each defoliation class.