Per a very educational poster presentation at the last Great Lakes Expo, grape berry moth (GBM) remains a major pest management challenge for grape growers across eastern North America, causing economic losses and driving many of the insecticide applications in the region’s vineyards.
There is an urgent need for strategies to improve control and reduce the financial and environmental costs of managing GBM, according to Michigan State University’s Jacquelyn Perkins and Rufus Isaacs, from the Department of Entomology.
Their research trials have been evaluating different IPM programs to determine how they perform in Michigan vineyards against GBM, including testing monitoring methods and newer insecticides.
Their goals were to determine if lures with different GBM pheromone loads could improve monitoring and to compare spray programs to determine which insecticides were most effective on GBM at particular application timings.
Four farms in Van Buren County growing Concord, Niagara and/or Chancellor grapes were part of the trial and weekly scouting took place between May and September. The vineyards received either the grower’s standard insecticide program or an MSU-developed IPM program based on regular scouting updates.
Researchers looked at the number of GBMs caught in traps, the percentage of grape clusters with moth damage, the number of damaged berries per damaged cluster and other notable insect pest damage.
Grape berry moth. Photo courtesy of Todd M. Gilligan & Marc E. Epstein, USDA-APHIS PPQ, Bugwood.org
Specifically, the GBM lure trial took place at four vineyard sites in Lawton, MI, close to stands of woods. The traps were placed along the vineyard edge and had one of six different pheromone concentrations or the commercially available standard lure from Great Lakes IPM.
Each week during the trial, the number of moths in each trap was counted, the trap liners were replaced and trap locations were rotated. Lures were replaced every four weeks during the span of the trial.
The traps caught the most GBMs in June, but infestation levels increased throughout the growing season. The number of moths captured in traps each week was negatively correlated with percent cluster infestation in the same week, meaning monitoring traps are not the best way to predict GBM risk.
It turned out the commercially available GBM lure was the most effective for capturing the pest through most of the season. The lures with a range of pheromone concentrations were not more effective at capturing GBM during any moth generation in 2022.
When the research team compared the average percentage of clusters with GBM damage in two Niagara vineyards at the same farm that received different spray programs, the biggest difference was seen toward the end of the trial.
In that grower’s standard spray program, 10% of clusters sprayed with Mustang Maxx had GBM damage on Sept. 2 while only 5% did in the MSU program. Likewise, at harvest on Sept. 28, 13% of standard program clusters had damage; only 7% did in the MSU program.
The MSU program spray demonstrations indicated that Verdepryn, Voliam Flexi and Intrepid Edge are effective reduced-risk insecticide options for controlling this pest.
Overall, high pressure vineyards had an average of 15% of their grape clusters with GBM damage at harvest time in 2022. The researchers suggest using degree day models for insecticide timing and ensuring good coverage with effective products for GBM control.
They concluded that it’s highly recommended grape growers conduct visual GBM damage assessments in their vineyards throughout the growing season to figure out what their current pest pressure is and how well their spray programs are performing.
