The roles of physical damage and burial in managing grape berry moth (Paralobesia viteana) with tillage

Southwest Michigan is the largest area of juice grape production in the North Central Region. Management of grape berry moth (GBM), Paralobesia viteana, is a concern for grape growers in this region. GBM is a direct pest that oviposits in berries. Larval feeding makes fruit unacceptable for processing. The last generation of the growing season overwinters as pupae in leaf litter. Decreasing the number of pupae that survive to the following spring reduces GBM pressures and improves the efficacy of integrated pest management. We investigated the use of late season tillage as a non-chemical technique for reducing pupal survival using two separate experiments. In the first experiment, GBM pupae were run over with a single pass of a Lilliston style cultivator. Overall, 72% of the pupae were buried; the majority between 1 and 5 cm. The maximum recovery depth was 7.6 cm. Tillage did not significantly increase damage to the pupae, cocoon, or litter material, nor did it impact survivorship of recovered pupae. In the second experiment, GBM pupae emerging from diapause were buried under 1,3,5, and 15 cm of sand and compared against an unburied control. Emergence was tracked for 6 weeks. No pupae survived burial at 15 cm. Emergence from the 1,3, and 5 cm treatments was statistically equivalent. Mean survivorship ranged between 7 and 16%, compared to 72% survivorship in the unburied control. These results indicate that tillage can reduce GBM overwintering survivorship on vineyard floors due to burial, but not damage.