Controlling grape root borer with pheromones
The grape root borer is an insect pest native to the Eastern U.S. The larval stage of the moth can do significant damage, living at least three years and possibly longer in the soil feeding on grape roots. They can destroy and kill mature grape vines. The most widely used control method involves using a restricted-use organophosphate pesticide, which is expensive and time consuming. Recently a new pheromone system has become available for use in grape root borer mating disruption. This system utilizes the pheromone mix of the European leopard moth, which differs from the pheromone mix in the standard grape root borer pheromone lure. Each of the new pheromone dispensers contains 80 times more pheromone than the standard grape root borer pheromone lure currently available. The new dispensers are labeled to be placed in the vineyard at a concentration that releases 300 times more pheromones than the standard grape root borer pheromone lures used in our previous NESARE projects. The effectiveness of the new pheromone system has previously been determined to be successful with the inability to trap male grape root borers in a vineyard. Utilizing trap shutdown as a marker for mating disruption success is questionable.
Grape root borer populations in our vineyard never decreased utilizing the standard pheromone lures in previous projects. The aim of the multi-year project will be to test the new system at different rates and its effectiveness in reducing or eliminating grape root borers in our vineyard. The new pheromone system will be utilized for two years. In the third year only traditional pheromone traps will be placed in the vineyard to determine if the new pheromone system has been successful.
In the summer of 2015 the initial tests on the effectiveness of the Isomate GRB pheromone dispensers was initiated. The vineyard test area was divided into 9 blocks with 3 plots each. On June 19, a standard bucket trap with a grape root borer pheromone lure was placed at the center of each plot. The traps monitor the effectiveness of the Isomate GRB dispensers. A grape rot borer male was first observed flying in the vicinity of trap on June 30, but none had been captured. The Isomate GRB dispensers were placed in the vineyard on July 1 in a randomized complete block design. Nine plots received no dispensers, while dispensers were placed in nine other plots at a rate of 25 per acre. The last nine plots had a dispenser density of 50 per acre.
On July 12, one male grape root borer was caught in a plot with no Isomate dispensers. The density of Isomate dispensers was increased that day. Nine plots still contained no dispensers. The nine plots with 25 dispensers per acre was increased to 50 per acre and the nine plots with 50 dispensers was increased to 100 per acre. Another male grape root borer was captured on July 18 in a plot with no Isomate dispensers. The density of Isomate dispensers was again increased. The plots with no Isomate dispensers was discontinued because plots with the highest number of dispensers per acre would now exceed the recommended density of 100 per acre. The plots with no dispensers was increased to a density of 50 dispensers per acre and the plots with 50 dispensers per acre was increased to 75 per acre. Plots with a density of 100 per acre remained unchanged. At this point the test area had an average density of 75 Isomate dispensers per acre. No additional male grape root borers were captured in the traps for the rest of the season.
Pheromone traps were also placed outside of the vineyard to determine if the Isomate dispensers would influence the area outside of the vineyard. Traps were placed at 200 foot intervals up to 1000 feet from the vineyard. The traps were situated in four directions from the vineyard; north, east, south and west. The traps with pheromone lures were placed on July 6. The first moth was captured in a trap on July 10, 1000 feet from the vineyard. The Isomate dispensers appeared to have some effect on the surrounding area. Over the entire season a total of 3 moths were captured 200 feet from the vineyard, 4 moths at 400 feet, 4 moths at 600 feet, 3 moths at 800 feet and 12 moths at 1000 feet.
A total of 16 Isomate dispensers were placed at other location, miles from the vineyard, to measure the loss of pheromones over time that are emitted from the dispensers. The study was initiated on July 3 and the dispensers were weighed weekly until September 14. Over this time period each dispenser lost about 0.002 grams of pheromone per week.
The Isomate grape root borer dispensers definitely caused a substantial decrease in the capture of male grape root borers in the pheromone traps. In most years at least 300 male grape root borers are captured in our vineyard. Isomate dispensers do create trap shutdown, but does trap shutdown mean males cannot find females? Is grape root borer mating still occurring? A mating pair of grape root borers was observed on July 26 just 14.5 feet from an Isomate dispenser. This observation would indicate that mating is still occurring in close proximity to Isomate grape root borer dispensers.
Penn State University
1383 Arcadia Road
Lancaster , PA 17601-3184
Office Phone: 7173946851