Control of grape root borer

1. Report Summary

Grape root borer is one of the most serious insect pests of grapes in the eastern United States. The goal of this project is to find a sustainable method of control using pheromone traps. A total of 81 traps were placed in the experimental area of 2.41 acres in the three acre vineyard using a randomized complete block design. Three different colors (standard-yellow with green and white, all green and all white) of traps placed at three different heights were located in the vineyard in 2003 and 2004. The standard traps captured the greatest number of moths and were usually the best statistically in both 2003 and 2004. The white traps had consistently caught the lowest number of moths and were the least effective statistically. With the removal of the all white traps and the addition of all yellow traps, no statistical significance was found in the color treatments in 2005 or 2006. The all yellow traps caught the greatest number of moths in 2005 but the yellow and standard traps caught almost identical numbers. In 2006, the standard traps caught the greatest number of moths, while the yellow traps captured the least. The presence of the color yellow in a trap still appears to be of importance.

Based on statistical analysis in 2005 and 2006, the height treatments are significant. The high placement of 70 inches and the medium placement of 44 inches were significantly better than the low placement of 18 inches with the AgStats02 program in 2005. The same result occurred in 2006. In 2003 and 2004 the height treatments were rarely significant. After selecting the proper color of traps, placement of the traps on the top wire at 70 inches could be considered of secondary importance.

Mating disruption still appears to be a possibility, although the total number of moths captured has not decreased since the initiation of the project in 2003. Since the first trapping began in 2003, the total number of grape root borers captured has remained relatively constant. If no trapping had been done in the vineyard, the number of grape root borers would be expected to be much higher by 2006. Based on a model growth curve constructed for this study and other sources, the total number of grape root borers captured should be approximately 51% greater by 2006 then the number actually captured. The grape root borer in the northern portion of of its range (Pennsylvania, New Jersey and Maryland) can have a three year or possibly even longer larval life cycle. With a three year or longer larval lifespan, if mating disruption is possible, reductions in the number of grape root borers captured should be seen in future years. The production of grapes indicates trapping has been helpful in reducing the total number of grape root borers in the vineyard. Production and vigor of the vines has increased during the four years of the project showing the beneficial aspects of the pheromone trapping.

2. Goals

Little work has been done on grape root borer (Vitacea polistiformis) in Pennsylvania. Several methods are available to trap and enumerate the adult male grape root borer with pheromone lures. We have worked with different trapping methods in our vineyard. This project continues three previous SARE grants, FNE03-471, FNE04-520 and FNE05-550. One of the main goals of this project has been to determine if the color and placement of moth traps are significant variables. Results from 2003 and 2004 revealed the color of the trap is a significant parameter in the number of moths captured. In 2003 the standard (yellow with green and white) and green traps were significantly more effective than the white traps and in 2004 the standard traps were significantly better than the green or white traps. With the removal of the white traps from the experiment and the addition of all yellow traps in 2005, trap color was no longer a significant variable. In 2003 and 2004, the placement of the traps was rarely significant. Each year the data is evaluated using two different statistical programs. The high placement of traps was significantly better than the medium or low placement in 2004 with one statistical program, but not the other. When the white traps were removed from the experiment in 2005, placement became a significant variable. Depending on the statistical program used, the high and medium placement or just the high placement were significantly better than the low placement.

The current SARE project will continue to build on the previous work. Trap colors utilized in 2005 will be repeated to ascertain if those colors are no longer significant. Trap placement will also remain the same to check if there is any significant difference. Another main goal of this project is to determine if mating disruption is possible with high numbers of pheromone traps in a vineyard. Because of the multiple year life cycle (at least three years) of the grape root borer, an extended testing period is required. If mating disruption is possible as a control measure, the need for pesticides would be eliminated.

3. Farm Profile

I am a part-time farmer currently farming 5 acres with my brother. The land is rented from our mother. The total size of the present farm is only 7.8 acres, although it has been cultivated by our family for seven generations. There is no house on the premises, only a 40' by 60' tobacco barn. My brother and I first planted wine grapes on the farm in 1974. Today a total of 3.5 acres is planted in wine grapes and includes the French hybrids: seyval, vidal and chambourcin. The vidal was planted in 1976, chambourcin in 1980 and seyval in 1984 and 1986. Vines are grown with unilateral or bilateral cordon training on the bottom wire. A standard three wire system with wires at 36, 54, and 72 inches is used for the trellis. The vines are trained using vertical shoot positioning. Vineyard spacing is 9 foot wide rows with 6 feet between the vines in the row. An area of approximately one half acre is used for the growing and production of grafted vines and other varieties. Since 1989 I have also grown one half acre of saffron on the farm.

The farm is composed entirely of Duffield silt loam with a 0 to 3% slope on the top of a small hill. The location provides excellent air drainage with no frost pockets. The surrounding area is almost entirely in farmland and is located in an agricultural security area. There have been no changes in the operation since the initiation of the SAKE project.

4. Participants

The technical advisor for this project is Mark Chien of Pennsylvania State University . Since 1999, Mark has been the wine grape agent for Penn State Cooperative Extension. Currently he is serving all of Pennsylvania. Another advisor on the project is Dr. Michael Saunders of the entomology department at Pennsylvania State University. One area of his research involves the ecology and pest management of arthropods affecting vineyards and refining existing grape management practices. His extension work covers integrated pest management in viticulture. Dr. Saunders will provide expertise in experimental design and statistical analysis of the data.

5. Project activities

Results from the 2003 and 2004 SARE projects revealed the color of the trap can be a significant variable in the number of moths captured. A complete statistical analysis of the data revealed the standard and green traps were significantly more effective than the white traps in 2003 and in 2004, the standard traps were more effective than the green or white. In 2003 and 2004 the white traps were the least effective of the three colors. The following year, in 2005, the white traps were removed from the study and replaced with a completely yellow trap. With the removal of the white traps in 2005, trap color was no longer statistically important, but trap placement became statistically important. Depending on the statistical program used, the high and medium placement or just the high placement were significantly better than the low placement.

The goals of the project have been to maximize the capture rate by determining the best color and placement of traps and to ascertain if mating disruption is possible with a high number of traps. The experiment was designed to attempt capture of all male moths with sufficient replicates for statistical analysis. In 2003 and 2004, 31% of the traps caught no root borers at all. When the white traps were removed in 2005, the number of traps catching no root borers was decreased to 9%. The experimental design from 2003, 2004 and 2005 was repeated in 2006 using the same plots and blocks with the traps placed in a new random selection. The variables tested were trap color and placement. A randomized complete block design was developed for each variable. The experimental area covered 80% of the vineyard.

The same trap colors utilized in 2005, yellow, standard (yellow with green and white) and green, were retested in 2006. Standard and green plastic universal moth traps are available from Great Lakes IPM (Vestaburg, Michigan). The all yellow traps were purchased from Advanced Pheromone Technologies, Inc. in Marylhurst, Oregon. A total of 81 traps were placed in the vineyard or 27 of each color - yellow, standard and green.

The vineyard was divided into 27 blocks of 72 feet by 54 feet or 3888 square feet per block. Each block was divided into three plots of 18 feet by 72 feet or 1296 square feet per plot. A trap was suspended on the trellis at the center of each plot. Every block received the three different colors. The color of each trap placed in the plots of each block was selected using a ten thousand random digit table.

Three different trap height placements were selected for testing in 2006. The same heights used in 2003, 2004 and 2005 were repeated. Traps were placed 18 inches above the ground or below the vine canopy, 44 inches above the ground or in the middle of the canopy close to the fruiting zone and 70 inches above the ground or at the top of the vine canopy. The distance from ground level was based on the position of the pheromone lure.

For trap height the vineyard was divided into 9 blocks of 162 feet by 72 feet or 11,664 square feet per block. Each block was divided into three plots of 72 feet by 54 feet or 3888 square feet per plot. Each plot for the trap height experiment was the same as a block for trap color. Within each plot for trap height, the three traps received the same height. For each of the three trap heights there were 27 replicates, three in each plot. The height of the traps in the plots of each block were selected using a ten thousand random digit table.
The traps were placed in the vineyard on June 17th according to the experimental design. A 10% DDVP toxicant insecticide PVC tape measuring 1 inch by 4 inches was placed inside each trap to kill any moths that entered. A pheromone lure for grape root borer was place in the lure holder of each trap. The traps were checked every three or four days or twice a week from June 17th until September 3rd, with the moths captured recorded on data sheets.

6. Results

In our vineyard, the first male grape root borer moths were recorded on July 2nd (2 moths) and the last August 26th (1 moth) with the highest catch on July 15th with 104 moths. A total of 243 moths were captured in 2006, an 8.6% decrease from the total captured (266 moths) in 2005. In 2004 a total of 144 male grape root borer moths were captured and in 2003, 224 moths. This variability in the total number of male grape root borers captured each year is not unexpected. There is a very high mortality of eggs and newly hatched larvae that can vary significantly from year to year depending on many factors such as the weather and the presence of predators during egg development and hatching. In the northern regions of the grape root borer range (Pennsylvania) most of the larvae probably have a three year or longer life cycle.

Table 1. Major Catch Dates for 2006
Date Total moths captured
7-5 1
7-8 10
7-11 25
7-15 104
7-18 25
7-22 36
7-25 15
7-29 13
8-1 6
8-5 0
8-8 5

The initiation of moth emergence, date of highest catch and the end of moth emergence can also vary from year to year. During the four years of this project, the date of first capture has been from June 28th to July 5th. For three of the four years the date of the highest catch has been in mid-July and the other year was in early August. The date of last capture has varied from August 7th to August 30th.

Statistical analysis was performed on the data with just one program in 2006. In previous years two programs were utilized, but one program was not available this year. The agricultural statistics analysis program (AgStats02) provided by the Pacific Northwest Conservation Tillage Systems Information Source at http://pnwsteep.wsu.edu/agstatsweb was utilized. This program allows up to 16 treatments and 16 replicates and performs an analysis of variance. The level of significance can be selected at 1%, 5%, 10% or 20%. All data entered with this program utilized the randomized complete block design option.

The height treatment data in the statistical program has been entered as low (18 inches above ground level), medium (44 inches above ground level) and high (70 inches above ground level).

Table 2. Height Treatments 2006
high 70" 90 moths
medium 44" 101 moths
low 18" 52 moths

This was the first year out of four in which the high placement did not capture the greatest number of moths. Using the AgStats02 with nine replicates, the high placement at 70" and the medium placement at 44" were significantly better than the low at a 5% level of significance. The same result occurred in 2005.

Table 3. AgStats02 Height Treatment 2006
LSD (least significant difference) 3.53
Treatment Mean
high 10.00 a
medium 11.22 a
low 5.78 b

5% level of significance

Color treatments are entered in the statistical program as yellow, standard (yellow with green and white) and green.

Table 4. Color Treatments 2006
yellow 71 moths
standard 95 moths
green 77 moths

The experimental design for each color treatment (yellow, standard and green) contained 27 replicates. Unfortunately the AgStats02 program allows only 16 replicates. To run this program the three replicates of each color in each height block were combined. The three treatments (yellow, standard and green) were entered with nine replications. At a 5% level of significance, no significant difference was found in the 2006 color treatments with the AgStats02 program. The same result occurred in 2005.

An analysis of variance (AgStats02) for the combined treatments (height and color) was performed. For this statistical analysis, nine treatments were entered with nine replications. Within each height treatment block (162 ft. by 72 ft.) there were all nine possible combinations of height and color treatments. At a 5% level of significance the medium standard was significantly more effective than any other treatment.

Table 5. AgStats02 Height and Color Combined Treatments 2006

LSD (least significant difference) 1.97

Treatment Name Mean
low green 1.89 a
low standard 1.89 a
low yellow 2.00 a
medium yellow 2.33 a
high standard 3.11 a
medium green 3.33 a
high green 3.33 a
high yellow 3.56 a
medium standard 5.56 b

Based on statistical analysis in 2006, the height treatments are significant. The high placement of 70 inches and the medium placement of 44 inches were significantly better than the low placement of 18 inches in the AgStats02 program. The same result occurred in 2005. Previous to 2006, the high placement always had the greatest number of moths captured, although not always in significant numbers. In 2006, for the first time, the medium placement captured the highest number of moths.

The color treatments of standard, yellow and green had no statistical significance in 2006. The same result occurred in 2005. In 2003 and 2004, the color treatments were significant with different colors. The standard (yellow with green and white) traps did capture the greatest number of moths in 2006, the same result as in 2003 and 2004. In 2005 the all yellow traps caught slightly more moths than the standard traps, but in 2006 captured the least root borers.

Three varieties of French hybrid grapes; seyval, vidal and chambourcin are planted in the vineyard. The experimental design was developed primarily to test if adult male grape root borer moths would have a preference for different pheromone traps based on color and location. The initial plan called for an attempt to determine if grape root borers have a preference among the three varieties planted in our vineyard. Unfortunately the experimental design only allows a comparison to be made between the seyval and vidal.

In an analysis of variance (AgStats02) based on variety preference, two treatments were entered with eight replicates. No significant difference was found between the two varieties, even at a 20% level of significance. The same result occurred in 2003, 2004 and 2005.

7. Conditions

On May 30, 2006, the entire adjoining 37 acre farm was sprayed with a herbicide mix containing the amine form of 2,4-dichlorophenoxyacetic acid (2,4-D) because of its enrollment in the Conservation Reserve Enhancement Program (CREP) administered by the Farm Service Agency of the USDA. Grapevines are extremely sensitive to small amounts of phenoxy-type herbicides through both spray drift and volatilization of the chemical due to high temperatures. That day the high temperature reached 93°F for over one hour. By June 8th, herbicide damage due to 2,4-D was visible on the grapevines. On June 22nd, employees of the Pennsylvania Department of Agriculture took samples of grape tissue for herbicide testing. Analysis of the grape leaves found 2,4-D present at a concentration of 0.009 parts per million. A trace amount of 2,4,5-trichlorophenoxypropionic acid (2,4,5-TP), which was banned in 1985, was also found in the grape leaves. The exact effect this herbicide exposure might have on the grape root borer testing for 2006 is difficult to determine, but is probably negligible. If serious damage occurred to the vines it should become apparent in 2007.

8. Economics

Although the project was not structured for economic analysis, some trends are apparent. Since the introduction of universal moth traps to the vineyard production has increased with some yearly fluctuations. Many other variables, such as weather or lack of disease pressure, could account for the increase, instead of the presence of moth traps. With the increase in production, total farm income has also increased. The production of chambourcin, our most valuable variety, peaked in 1996 at 5.5 tons total production. By 2002 when two universal moth traps were placed in the vineyard, production had declined to 1.4 tons. Over the next two years, when 81 traps were in the vineyard each year, production increased 184% to 3.97 tons. Since 2004, the production of chambourcin has remained relatively constant with minor fluctuations. Production of vidal increased each year since the project started until 2006. The decrease in vidal production could be attributed to the 2,4-D exposure in late May 2006. Vidal, with its reduced vigor, appeared to be the variety most affected by the exposure.

Table 6. Grape Production in Tons 2002-2006
Variety 2002 2003 2004 2005 2006
chambourcin 1.4 2.8 3.97 3.7 3.8
vidal 3.9 6.2 7.4 9.2 7.8

9. Assessment

Results from 2006 confirmed the results of 2005, the placement of traps can be significant. With the AgStats02 statistical program, the high and medium placement were significantly better than the low placement in 2006, the same result obtained in 2005. Each year since the initiation of this project in 2003 the high traps have captured the greatest number of moths, except in 2006. The medium placement traps caught the highest number of moths in 2006, but significantly different as compared to the high traps. With the low traps being significantly less effective than the high or medium traps for two years in a row, they should be removed from the experiment. A new trap placement between the high and medium traps will probably be used in the future to maximize the capture of male grape root borers.

In 2006 no significant difference was found in the color treatments, the same result as in 2005. The standard or the yellow traps have captured the greatest number of moths each year since the initiation of the project. In terms of color, the presence of yellow still seems to be an important parameter, although the yellow traps in 2006 did capture the lowest number of moths. The standard traps caught the highest number of moths in 2006. Testing will continue next year with the same colors to verify the previous results.

Distribution of grape root borers in a small area can be very random. In the experimental test area of 2.41 acres, there were plots with no root borers and other areas of higher concentrations. In both 2003 and 2004, 25 traps or 31% caught no root borers during the 2.5 months of trapping. The number of traps catching no root borers in 2005 decreased to just 7 or 9% of the total traps. In 2006,10 traps or 12% of the total traps caught no root borers. There is no apparent reason for this change other than the removal of white traps from the experiment in 2005.

Plots with high concentrations of captured moths continue to decrease. In 2003, 4 traps or 5% of the total traps captured 25% of the moths. The four highest trap catches in 2003 were 17,15, 14 and 10. In 2004, 4 traps or 5% captured 20% of the moths and the two highest trap counts were 8, followed by 7 and 6. Four traps or 5% captured 16% of the moths in 2005 and the four highest trap catches were 14,11, 9 and 8. This trend continued in 2006 with 4 traps or 5% capturing 14% of the moths and the four highest trap catches were 10, 9, 8 and 8. Over the four years of testing it would appear the moths are becoming more and more diffuse throughout the vineyard.

10. Adoption

The results after four years of the project are still encouraging. The standard or yellow traps continue to capture the most moths, but no longer in statistically significant numbers. In 2005 the yellow traps captured the greatest number of moths, while in 2006 they were the least effective. When the white traps were removed from the experiment in 2005, color was no longer statistically important. With the three colors of traps used in the experiment showing no statistical difference, the trap color will remain unchanged.

Height placement was statistically significant in 2006. The high and medium placements were significantly better than the low placement. Results from 2006 verified the results from 2005 that height placement can be statistically significant. With two years of results verifying the statistical importance of the high or high and medium height placements, the low placement will be removed from the experiment to maximize moth captures. A new height placement between the former high and medium placements will be utilized in 2007.

Mating disruption still appears to be a possibility, although the total number of moths captured each year has not changed substantially.

Table 7. Total Male Grape Root Borers Captured 2003 2004 2005 2006
224 144 266 243

The relatively stable number of male moths captured does not mean mating disruption is unattainable. During the first two years of the study, all variables remained the same and the number of moths captured decreased 36%. White traps were used in the first two years and they were proven to be statistically ineffective at capturing moths. The white traps were removed from the study in 2005 and the total number of moths captured increased, but the effectiveness of all the colors also increased with no statistical difference being present.

During the third and fourth years of the study all variables remained the same and the number of moths captured decreased 8.6%. The low placement of traps has been proven to be statistically ineffective at capturing moths. Removal of the low placement should increase the effectiveness of the traps at capturing grape root borers.

The grape root borer in the northern portion of its range (Pennsylvania, New Jersey, Maryland) can have a three year or possibly even longer larval life cycle. During the four years of the study, the total number of male moths captured has not increased substantially as the trapping methods have been improved. If no trapping had been done in the vineyard, the number of grape root borers would be expected to be much higher by 2006.

The production of grapes indicates trapping has been helpful in reducing the total number of grape root borers in the vineyard. Production and vigor of the vines has increased during the project. Chambourcin production went from 1.4 tons in 2002 to 3.8 tons in 2006 and vidal increased from 3.9 tons to 7.8 tons in the same time period. With at least a three year larval lifespan, if mating disruption is possible, reductions in the number of grape root borers captured should be seen in future years. Just the increase in production has shown trapping to be beneficial.

11. Outreach

A half hour power point presentation on the 2003, 2004, 2005 and 2006 SAKE projects was presented at the 2007 Mid-Atlantic Fruit and Vegetable Convention on January 30, 2007 in Hershey, Pennsylvania. The meeting is sponsored by the State Horticultural Society of Pennsylvania, Pennsylvania Vegetable Growers Association, Maryland State Horticultural Society and New Jersey Horticultural Society. Approximately 100 people attended the talk, with attendees from Pennsylvania, Maryland and New Jersey. A ten page report based on the 2003 through 2006 SARE sponsored research was written for inclusion in the proceedings of the meeting published by the State Horticultural Society of Pennsylvania.

A copy of the ten page report was also sent to Mark Chien, wine grape agent for Pennsylvania working with Penn State Cooperative Extension.