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. Cooperators: T.N. Taft Jr., Field Assistant III, NYSAES, Fredonia, S. Katti, Dept. of Entomology, Penn State University and R. Dunst, Research Support Specialist, NYSAES, Fredonia. INTRODUCTION      The Grape Berry Moth Risk Assessment (GBM RA) protocol was developed 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 Martinson et al. (1991). 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.

Over the last four growing seasons, 'Concord' growers in the Lake Erie region have become concerned with an increase in late season berry damage. In 1997, a reexamination of current GBM management practices began by using pheromone trap catches and assessments of cluster and berry damage in three high risk vineyards across the Lake Erie Region, in an attempt to determine if a third generation of GBM caused this late season damage. Sampling just before harvest showed all three sites were well above federal inspection standards for insect damage (1% damaged berries by weight).

Trap catches were used to define the first generation but were unreliable for determining the activity of the 2nd and 3rd generations of moths. The first generation peak occurred significantly earlier (~325 GDD base 50 F) than predicted by the growing degree day (GDD) model developed by Hoffman and Dennehy (~603 GDD base 50 F). Based on the assumption set by Hoffman (1990) that peak egg laying occurs 8 days after peak trap catches, in 1997 the 10-day postbloom insecticide application was too late to target first generation egg laying.

Extensive trapping and damage monitoring was conducted in 1998 to examine patterns in male pheromone catches and berry damage. This reevaluation of GBM flight activity and berry damage examined the distribution of damage in vineyards along North-South and East-West transects of the Lake Erie region.

METHODS

This project was conducted in conjunction with a larger project, Understanding Variation in Grape Berry Moth Flight Activity and Implications for Pest Management, led by Greg English-Loeb, Entomologist, NYSAES, Geneva, NY and funded through the New York Wine and Grape Foundation and the Lake Erie Regional Grape Program Processor Group. This project was designed to describe variation in spring flight activity, its relationship to the number of generations in a season and to correlate male pheromone trap catches with female activity.

Pherocon® grape berry moth pheromone traps were placed in 15 high risk vineyards in the Lake Erie region. The Lake Erie Belt was divided East to West (following the Lake Erie shoreline) into 5 transects (North East, PA; Westfield, Portland, Fredonia and Irving, NY). Three vineyards were chosen along each transect, representing the lakeshore, lakeplain and escarpment. At each site, a trap was placed at the edge of the woods and one trap was placed in the vineyard approximately 25ft from the edge of the vineyard. All traps were examined three times a week from May 6 through September 21 and the number of grape berry moth captured was recorded.

At each site, shoots on ten vines were tagged, so that approximately 50 clusters total were tagged along the edge of each vineyard. These clusters were monitored weekly from June 29 to September 10 for GBM damage. Each cluster was examined and any damaged berry was recorded and removed, to prevent damage of multiple berries from the same larva. This allowed for GBM berry damage to be closely monitored throughout the season to determine when most of the injury was occurring.

To assess the amount of damage just prior to harvest in each block, 25 clusters were randomly collected from the wooded edge of each block around September 10 where damaged berries were not removed. Each cluster and berry was examined for damage and percent damage was recorded for each site.

HOBO® temperature probes were placed at 11 sites, Northeast Weather Association (NEWA) weather equipment already existed at the remaining 4 sites. Growing degree days were calculated for each site throughout the season. Growing degree days are a method of measuring heat accumulation throughout the season by averaging the daily high and low temperatures then subtracting the base temperature, in this case 50 F. This information was compared to peak trap catches and berry damage.

RESULTS

Generation peaks were difficult to determine using pheromone trap catches again in 1998. There appeared to be as many as five flights of male moths throughout the season. Moving averages of trap catches were calculated by summing the trap catches on a particular date with those of the two dates following, for each date traps were checked. Moving averages accentuate high and low trap catches and therefore, aid in the identification of peaks in flight activity. Figure 1 illustrates the five flights of male moths from the North East Route 20 site and is representative of the pattern observed at the majority of sites.

North East Rt 20

As in years past, late season Grape Berry Moth damage was abundant. Figures 2 and 3 show that in late August/early September the weekly berry damage was very high compared to the rest of the season. This late season increase in damaged berries occurred in 12 of the 15 sites.

Irving Rt 5

Fredonia Rt 5

According to Hoffman (1990), insecticide applications should target the three major egg laying events throughout the season. Peak egg deposition occurs approximately 8 days after male trap catch. The peaks in stung berries removed weekly, represent peaks in 1st instar larval activity. Ideally the insecticide application should be made just prior to the larval feeding to target eggs. In 1998, average bloom date was recorded on June 5. Based on this, the 10-day postbloom spray should have been applied on or about June 15, with the two other applications made the first and last week of August, if necessary. These sprays appear to provide adequate protection against egg hatch and subsequent larval feeding for 1998.

Percent cluster and berry damage was determined in each block from the weekly examination of the approximately 50 clusters that were tagged along the wooded edge of each vineyard. In these tagged clusters, the damaged berries were removed once identified to prevent further berry injury by the same larva. Accumulating the weekly damage provides total percent berries and clusters damaged throughout the season. Percent berry and cluster damage was also determined by collecting a preharvest random sample of 25 clusters from each vineyard. Table 1 compares the results of both sampling methods. The percent berry damage from the preharvest samples was significantly higher than the cumulative damage calculated from the tagged clusters. Thirteen of the 15 vineyards were above the federal inspection standards for insect damage (1% damaged berries by weight) for processing grapes.

1. Moths move from the woods early in the season into the vineyard by late season. On average, 73% of first flight (5/6-5/29) pheromone catches were made in the woods traps and 82% of fifth flight (9/2-9/21) pheromone trap catches were made in the vineyard traps. This steady movement from the woods into the vineyard throughout the season was observed in 13 of the 15 sites.
2. Larva feed on and damage multiple berries. The percent berry damage of clusters that were collected preharvest was, on average, 83% higher than the percent berry damage from clusters where damaged berries were removed to prevent multiple berry injury from the same larva. Eleven of the 15 vineyards exhibited higher damage in the preharvest samples. Larva feed on and damage multiple berries. The percent berry damage of clusters that were collected preharvest was, on average, 83% higher than the percent berry damage from clusters where damaged berries were removed to prevent multiple berry injury from the same larva. Eleven of the 15 vineyards exhibited higher damage in the preharvest samples.
3. There does not appear to be significant differences in flight activity between vineyards on the lakeshore vs. lakeplain vs. escarpment. Nor does there appear to be significant differences in emergence from the eastern (Irving) to the western (North East) end of the belt.
4. The number of new berries damaged increases throughout the season, with minor fluctuations. Berry damage peaked in late August/early September. Ten of the 15 vineyard sites showed this distinct increase in late season damage.

DISCUSSION

Previous work studying grape berry moth has been designed under the assumption that there are two and possibly three, generations of moths emerging during the growing season. Based on this, each generation was targeted for management, if necessary. Through two years of reexamining male grape berry moth flight activity and looking at patterns of berry damage throughout the season, this simple two (or three) generation model does not seem to apply to vineyards in the Lake Erie region.

There are several hypotheses to explain the variation in flight activity that has been observed. Two of the most plausible are:

1. Spring emergence is quite variable and leads to wider variation by the end of the season, which would explain the constant flight activity by males.
2. Based on environmental and biological factors beyond the scope of this project, two "types" of grape berry moth are present in each vineyard, the first has three generations and the second has two (Gleissner 1943).

This second scenario would explain the five apparent flights during the season assuming the two types of moths emerge at different times in the spring. Presently we are unable to distinguish between the two scenarios.

The GBM RA protocol, developed by Hoffman and Dennehy (1987), was based on flight and ovipositioning data collected during 1987 and 1988. A major difference between Hoffman's studies and the results collected during this two-year reevaluation was that the first generation of moths collected in 1997 and 1998 was much earlier (~325 DD, ~400 DD respectively) than predicted by Hoffman (603 DD). Hoffman (1990) placed both pheromone traps in the vineyard (approximately 30 and 120ft from the vineyard edge). Whereas, in 1997 and 1998 pheromone traps were placed along the wooded edge and in the vineyard approximately 10m from the vineyard edge. It is possible that Hoffman didn't catch the first flight of GBM that was observed moving in from the woods. This would account for the discrepancy in early season trap data.

This project provided some insight into male flight and larval damage patterns. Though there appears to be 5 flights of male moths throughout the growing season, larval feeding on the berries is of the most concern. This larval feeding seems to peak 2-3 times during the season and in most cases berry damage reaches it's maximum in early September. This may be because the berries are more susceptible later in the season. As the berries increase in size, they come into contact with each other. A single hatching larva can easily damage more that one berry without moving a great distance. The Grape Berry Moth Fact Sheet (Riedl 1984) states "(larva) usually enter where berries touch each other or where berry is joined to the stem."

Examination of spray records collected from 5 of the vineyards has indicated that growers' spray schedules vary, typically cutting back to 1 or 2 sprays a season (typically only the 10-day spray) in high risk vineyards. It may be that 1 or 2 sprays could effectively manage grape berry moth damage if the insecticide application(s) were made in August, when the larva do the most berry damage. Spray trials should be conducted to examine the effectiveness of early, mid and late season sprays on management of late season damage.

The FQPA creates a unique problem for grape growers in this region as it could potentially eliminate all the major insecticides (Sevin, Penncap, Imidan, Guthion) currently used for grape berry moth management. The loss of these insecticides would make growers rely on Bt based insecticides. Previous spray trials with Bt revealed a need for two applications of Bt's for every application of conventional insecticide due to the mode of action and short residual of the Bt's. Therefore, correct timing of the application is critical.

The possibility of future restrictions on the use of conventional insecticides and the current lack of economic management of grape berry moth damage across the Lake Erie grape belt requires attention. Alternative management strategies which consider FQPA regulations need to be examined further.

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