Click on Titles: Grower Adoption of Grape IPM Disease Management Strategies Implementing GBM Risk Assessment and Leafhopper Scouting in Lake Erie Region Vineyards Exploring Alternative Methods of Implementing ISOMATE-GBM™ in High Risk Vineyards Reexamination of Grape Berry Moth Management Practices in the Lake Erie Region I Reexamination of Grape Berry Moth Management Practices in the Lake Erie Region II Postemergence Vineyard Weed Management Program I Postemergence Vineyard Weed Management Program II Food Quality Protection Act Back to GIPM Home Page Back to Lake Erie Regional Grape Program Home Page

Principle Investigators: T. Weigle, Sr. Area Extension Educator, NYS IPM Program, G. English-Loeb, Dept. of Entomology, NYSAES, Geneva, J. Bixby, Program Assistant, NYS IPM Program. INTRODUCTION      The Grape Berry Moth Risk Assessment (GBM RA) protocol was developed ten years ago by Hoffman and Dennehy (1987) to address the possibility of reducing the number of insecticide applications necessary to manage grape berry moth damage to economically acceptable levels. This program was initiated by the processors' desire to reduce pesticides due to public concern and the growers' desires to reduce production costs. The GBM RA protocol calls for a 10-day post bloom spray in high and intermediate risk vineyards. Low and intermediate risk vineyards are then scouted the third week of July to determine if an insecticide application is necessary during the first week of August. In high risk vineyards an early August insecticide application is made without sampling. Sampling during the fourth week of August is used in high risk vineyards to determine if a third insecticide application in late August is required.      Despite wide implementation of the Grape Berry Moth Risk Assessment protocol across the Lake Erie region, late season damage from the second and third generation of GBM has not been accurately predicted. This late season damage has become a concern for 'Concord' growers in the Lake Erie region over the last three growing seasons.

For GBM RA to successfully manage GBM damage, the vineyard must be scouted at the correct time, in relation to the life cycle of grape berry moth and the generation peaks in population. The current model predicts peak egg deposition as 8 days after peak trap catches.

Sprays should be timed to target the times of peak egg deposition. Currently, a growing degree day model is used to predict when each generation will emerge and peak. The third week in July and the fourth week of August were determined by Hoffman to represent the second and third generation peaks. However this model has not been proven reliable in the prediction of the second and third generation. Collecting data on GBM emergence, generation peak and damage and correlating this with corresponding growing degree days allows for a re-evaluation of the growing degree day model.

METHODS

     Pherocon® grape berry moth pheromone traps were placed in three vineyards in the Lake Erie region known to be at a high risk for GBM damage. Vineyards in Irving, Westfield and Fredonia, NY were chosen as test sites. At each site, one trap was placed at the edge of the woods and one trap was placed in the vineyard approximately 25 feet from the woods. Each Monday, Wednesday and Friday, from June 13 through September 19, all six traps were checked for grape berry moth and catch counts recorded.

     Grape Berry Moth Risk Assessment was done weekly from August 20 through September 10 at each site to determine the extent of cluster damage. Four sites were selected in each block, two along the wooded edge and two in the interior. At each site, 10 clusters were examined for GBM damage on each of 5 vines for a total of 50 clusters/site and 200 clusters per block. A threshold of one or more damaged berries/cluster was used to determine if a cluster was damaged.

     To assess the amount of GBM injury at or near harvest, 50 clusters were collected at each site, 25 from the edge and 25 from the interior on September 10. Each cluster and berry was examined for damage and percent damages were recorded for each site.

     To re-evaluate the growing degree day model currently used to monitor grape berry moth, GDDs were compiled for Irving, Westfield and Fredonia using weather station data from each site obtained through the North East Weather Association (NEWA) on-line bulletin board system. This information was compared with trap catches and cluster damage from GBM in each vineyard.

RESULTS

     Christopher Hoffman (1990) designed a growing degree model to reflect the life cycles of grape berry moth throughout the season. Comparing eleven years of temperature data and trap catches to GDD, Hoffman found that GDDs were the best predictor of when peak trap catches would occur, as opposed to using vine phenology and the calendar. Hoffman's studies showed the peak trap catch of first generation males occurs at approximately 603 DD (base 50 F) with peak egg deposition occurring 8 days later. To ensure proper timing, the insecticide application should be made prior to peak egg deposition.

     To test this model, pheromone trap catch data and growing degree day data were collected from the three sites during the 1997 growing season to determine if the spray timings dictated by the Grape Berry Moth Risk Assessment were providing adequate management of this pest. Figures 1, 2 and 3 show the data collected from these sites. The first generation is well pronounced with the peak occurring at 371 DD, 325 DD and 293 DD at the sites in Irving, Fredonia and Westfield respectively. However, the peaks of the second or third generation could not be easily determined from the trap catch data.

     Table 1 shows when peak egg deposition occurred at each site assuming Hoffman's findings that peak egg deposition occurs approximately 8 days after the peak trap catch. Bloom was recorded at the Fredonia Lab on June 26, 1997 (586 DD). The first insecticide of the season would have been applied across the region at 10 days post-bloom, following the Risk Assessment protocol. This spray would have been applied on July 6, 1997 (722 DD), 8-12 days too late to provide management of the first generation.

*Peak egg deposition occurs 8 days after peak male pheromone trap catch (Hoffman 1990)

     All three of the test sites were categorized as high risk vineyards. Sampling, in accordance with the Grape Berry Moth Risk Assessment protocol, was conducted from August 20 to September 10 to monitor late season damage levels (Table 2). On August 20, cluster damage was severe at all three sites, being well above the 15% threshold, and the damage levels rose significantly throughout the end of the season. On September 10, clusters were collected from the edge and interior of each site to determine the amount of berry damage. This pre-harvest sampling showed that all three sites were above industry standards for insect damage (1% damaged berries by weight).

*Cluster damage as determined by the sampling method used in the Grape Berry Moth Risk Assessment protocol.

DISCUSSION

     This project provided some evidence that grower concerns over late season grape berry moth damage are justified and that a broad reexamination of the Grape Berry Moth Risk Assessment Protocol was warranted. The results indicate that more detailed research needs to be conducted to better correlate pest biology, trap catches and growing degree days to understand the emergence of the GBM populations throughout the growing season.

     Using the GBM RA protocol for high risk vineyards resulted in a late application for the first generation of grape berry moth in 1997. A late application of an insecticide targeting the first generation would logically provide a higher survival rate of first generation larvae which should lead to a larger population in the second and third, if present, generations.

     The results of this project show that in years similar to the 1997 growing season, crop phenology and the GDD model developed by Hoffman (peak trap catch = 603 DD) are not reliable indicators on which to time sprays for grape berry moth. Peak catches with pheromone traps have been used in the past to help in timing insecticide applications of the second and third generations. However, as Figures 1-3 indicate, determining peaks for the second and third generation are difficult at best. A study conducted by Gleissner (1943) may provide some insight into the confusing trap catch data. Gleissner's study suggests the presence of two types of grape berry moth in this region. One type which produces two generations per growing season and one that produces three generations a year. This could explain the appearance of five peaks in Figure 1 (Irving). The Peaks at 6/20, 8/6, and 9/10 representing the three-generation type GBM, and the peaks 6/30 and 8/20 representing the two-generation type of GBM. Mixing of these two types of GBM within vineyards may explain why generation peaks are not easily determined by current standards.

     Although the scope of the project was limited to high risk vineyards, and there is only one year of data, there is enough information to justify a more extensive project examining grape berry moth biology and timing of insecticide applications using growing degree days and pheromone trap catches. Further research is needed to address the mis-timing of insecticide applications. Alternate spray programs comparing timing of insecticide applications based on growing degree days and/or peak trap catches versus the traditional crop phenology-based timings of the Grape Berry Moth Risk Assessment Protocol should be conducted.

References

Gleissner, B.D. 1943. Biology and Control of Berry Moth in the Erie Grape Belt. Pennsylvania Agricultural Experiment Station Bulletin Number 451.

Hoffman, C.J. 1990. Development and Validation of a Risk assessment Program for the Management of the Grape Berry Moth, Endopiza viteana (Clemens), in New York State. Ph.D. Dissertation, Cornell University.

Hoffman, C.J. and T.J. Dennehy. 1987. Assessing the Risk of Grape Berry Moth Attack in New York Vineyards. New York's Food and Life Sciences Bulletin Number 120.

Martinson, T.E., et al. 1991. Risk Assessment of Grape Berry Moth and Guidelines for Management of the Eastern Grape Leafhopper. New York's Food and Life Sciences Bulletin Number 138.

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