Improved monitoring, threshold development, and control of grape berry moth in wine grapes Rufus Isaacs 1, Keith Mason 1 & Luis Teixeira 1,2 1. Department of Entomology, 2. Current address: DuPont, Wilmington, DE. Contact isaacsr@msu.edu, for more information on this research project. ABSTRACT Grape producers continue to be challenged by grape berry moth infestation in clusters at harvest that can lead to greater cluster rots. In this study, yield was found to decrease with increasing GBM infestation, showing additional importance of controlling this pest. We have also made collections through 2011 of GBM collected from NW Michigan so that pheromone blends can be analyzed this spring. Comparison of insecticide programs for GBM control using reduced-risk insecticides applied using the degree day model showed improved insect control compared with the standard program. GOALS & OBJECTIVES This project aims to improve grape berry moth management so that its impact on grape production in Michigan can be reduced. Objectives: 1: Compare the pheromone blend of moths collected in NW and SW Michigan 2: Improve monitoring of grape berry moth in wine grape vineyards 3: Compare GBM moth control using insecticide treatments timed using the degree-day model RESULTS & CONCLUSIONS Examination of the pheromone blend is ongoing in the laboratory this spring (photo), so no results can be presented yet. The sites for trapping GBM in different locations did not yield high enough numbers of moths, so this objective will be repeated in 2012 at sites with higher pressure. We were able to sample vineyards for GBM infestation, and found a significant decline in yield with increasing GBM infestation. This relationship has been characterized, allowing development of economic thresholds for GBM sampling and integrated pest management programs, which indicate the importance of good fruit protection in sites with this pest present. Insecticides timed for GBM control using the degree day model outperformed standard insecticide programs. OUTCOMES This project will provide new insights for improving management of grape berry moth. Further examination of pheromone blends and monitoring methods will be required during 2012 to enable completion of some of our objectives. The comparison of GBM infestation in modeldriven and standard insect management programs is expected to lead to greater adoption of reduced-risk insecticides for control of grape berry moth. As the Extension materials associated with these studies are developed and distributed, we expect improved control of GBM. 1
PROJECT PERIOD This project was conducted during 2011. We plan to continue this research in 2012 to complete the analysis of GBM pheromone, sampling of vineyards for GBM moths and infestation, and development of provisional economic thresholds for testing within grape IPM programs. WORK ACCOMPLISHED DURING THE PERIOD 1: Compare the pheromone blend of moths collected in NW and SW Michigan During 2011, GBM-infested berries were collected from multiple NW and SW Michigan vineyards in the month prior to harvest, to enable comparison of the pheromone belnd of moths collected from the two regions. These larvae entered diapause and were held through the winter at 4 o C. In spring 2012, the pupae have been warmed to the point of emergence, and the emerging female moths have been collected and the pheromone glands removed when the moths are 1 day old (Figure 1). These samples are being held in a freezer and will be analyzed this spring for the pheromone composition using gas chromatography. This will be compared to the blend from moths collected from SW Michigan to determine whether there is a significant difference in the pheromone blends. 2: Improve monitoring of grape berry moth in wine grape vineyards We were not able to trap sufficient moths for comparison of trap locations as planned, so this experiment will be repeated during 2012 at sites with higher GBM pressure. Sampling of grape clusters for GBM infestation across vineyards with a range of infestation levels yielded a linear negative relationship between grape infestation levels and yield (Figure 2). This relationship will be used to determine the economic threshold for GBM which is the point at which the loss of crop revenue is equal to the cost of controlling it. Once 2012 field season data are available, this analysis will be conducted, taking the price of grapes and the cost of insecticides, labor, and machinery operation into account. 3: Compare GBM moth control using insecticide treatments timed using the degree-day model. During 2011, vineyards with a history of GBM infestation were managed using a program based on degree day model timing of new insecticides Brigadier at 5.1 oz/acre (bifenthrin+imidacloprid, FMC) applied at 10 days post bloom, Intrepid at 8 oz/acre (methoxyfenozide, Dow AgroSciences) applied at 810 GDD after wild grape bloom, and Altacor at 3 oz/acre (rynaxypyr, DuPont) applied at 1620 GDD after wild grape bloom. Intrepid and Altacor have long residual control, providing superior longevity against GBM during the long periods of egglaying in the summer. The broad-spectrum insecticide program consisted of Brigade at 3.2 oz/ace applied at 10 days post bloom, Sevin XLR applied at 64 oz/acre applied at 910 GDD after wild grape bloom, and Imidan at 2 lb per acre applied at1720 GDD. Results in 2011 mirrored the findings in previous growing seasons, funded under separate sources. The vineyards treated with Intrepid and Altacor had 60-80% lower infestation than did those receiving the standard program. By using the selective insecticides only in the regions of the vineyard where the pest pressure is greatest, i.e. the vineyard perimeters, we were also able to demonstrate that this program is more effective and less expensive. Considering only the insecticides, the average cost per acre was $51.24 for the standard program, compared with $32.68 for the reduced-risk IPM program. 2
COMMUNICATIONS ACTIVITIES, ACCOMPLISHMENTS, AND IMPACTS Presentations Integrating mating disruption, phenological models, and selective insecticides for sustainable grape berry moth management. 7 th International Integrated Pest Management Symposium. Memphis, TN. March 26-29, 2012. New insecticides and their fit for Michigan grape growers. Isaacs, R. Southwest Hort Days. Benton Harbor, Michigan. February 9 th 2012. Optimizing Pesticide Application in Vineyards. Summer grape field day. Berrien Spring, August 10, 2011. 40 attendees. Using The Grape Berry Moth Model for Improved Control. Viticulture Day, Southwest Michigan Research and Extension Center, Benton Harbor, Michigan. July 27, 2011. 200 attendees. Grape Berry Moth monitoring and management update. Lawton, Michigan. June 15, 2011. 50 attendees. Vineyard Insect Management Update. NWMHRS, Traverse City, MI. April 1, 2011 (presented by Duke Elsner). 30 attendees. Publications Teixera, L., Mason, K.S., Van Timmeren, S., and Isaacs, R. (2011) Seasonal pattern of oviposition by the North American grape berry moth (Lepidoptera: Tortricidae). Journal of Applied Entomology 135: 693-699. Gökçe, A., Isaacs, R. and Whalon, M.E. (2011). Ovicidal, larvicidal and anti-ovipositional activity of Bifora radians and other plant extracts to the grape berry moth Paralobesia viteana (Clemens). Journal of Pest Science 84, 487-493. Online information Regular updates through the 2011 growing season related to GBM management. FUNDING PARTNERSHIPS This project was co-sponsored by National Grape Cooperative during 2011. 3
IMAGES Figure 1. Pheromonee glands being extracted from grape berry moths collected in NW Michigan during 2011. 4
Figure 2. Relationship between infestation level by grapee berry moth and yield, from 28 vineyard locations sampled during 2011. This significant negativee relationship indicates that 50% cluster infestation translates to approximately 1 Ton per acre loss. 5
Figure 3. Infestation of grape clusters by grape berry moth at vineyard borders (left) and vineyard interiors (right), when managed using a standard broad spectrum insecticide program, or an IPM program based on a degree day model to time insecticides and use of the reduced-risk insecticides Intrepid and Altacor. 6