Michigan Grape & Wine Industry Council 2012 Research Report Understanding foliar pest interactions for sustainable vine management Rufus Isaacs 1, Steven Van Timmeren 1, and Paolo Sabbatini 2 1. Dept. of Entomology and 2. Dept. of Horticulture, Michigan State University, East Lansing, MI 48824 ABSTRACT This project investigated the response of wine grapes to potato leafhopper (PLH) and Japanese beetle (JB) feeding damage. After exposing vines to low and high levels of PLH and JB feeding damage, no discernible effects were seen on vine growth or clusters produced, however JB feeding damage did have some effect on fruit quality. Bioassays were also conducted to determine the residual effectiveness of insecticides against PLH and JB. Several of the insecticides provided excellent control against PLH and JB through 14 days after treatment. The longer residual effectiveness of some of these compounds gives growers greater flexibility when deciding what and when to spray insecticides. GOALS & OBJECTIVES This project aims to improve understanding of the effects that potato leafhopper and Japanese beetle have on grape vine health and fruit production with the goal of reducing insecticide inputs and increasing flexibility in timing of insecticide applications when they do become necessary. Objectives 1. Determine whether the combination of PLH and JB feeding causes greater reduction in vine growth and fruit quality than either pest alone. 2. Compare insecticides for their speed and duration of activity against PLH and JB. 3. Develop and implement a thresholds-based canopy management strategy for Michigan winegrape growers. OUTCOMES This project builds on our previous study on potato leafhopper-vine interactions that resulted in recommendations for less intensive management of PLH in vineyards. Results from the first year of this study indicate that Japanese beetle feeding can be managed less intensively as long as sufficient time is given for vines to recover later in the summer. PROJECT PERIOD This project was conducted during the 2012 season and will continue through the 2013 season. 1
WORK ACCOMPLISHED DURING THE PERIOD Objective 1. Determine whether the combination of PLH and JB feeding causes greater reduction in vine growth and fruit quality than either pest alone. A mature Pinot gris vineyard was used to for experiments investigating the effect of PLH and JB feeding damage on vine growth and fruit quality. In June 2012, vines were exposed to a high or low level of PLH feeding through selective application of insecticides to the vines. Vines exposed to a high level of PLH feeding had significantly more leaves with PLH-induced yellowing (6.6 ± 1.0 leaves) than those exposed to a low level of PLH feeding (0.19 ± 0.1). In July 2012, vines were exposed to a high or low level of JB feeding by placing adult JB onto half of the vines and covering those vines with floating row cover mesh to keep the beetles in place. Vines exposed to adult JB had a higher percentage of leaf area removed (44.6 ± 5.4 percent) than vines that were not exposed to beetles (2.5 ± 0.8 percent). To measure the effect that PLH and JB feeding on the health of the grape vines, five grape shoots per vine were measured at three times during the 2012 season. No significant differences were found among any of the treatments, indicating PLH and JB feeding damage did not have any effect on shoot growth. In addition, there were no significant differences among treatments in the total number of clusters per vine or the weight of those clusters at harvest. Three sets of grape berry samples were collected in August 2012 at three, two, and one week prior to the final cluster harvest on 5 September 2012. These berry samples and the final cluster samples were analyzed for Brix, ph, and TA levels in order to determine if PLH and JB feeding affected how the grapes ripened. The level of PLH feeding had no significant effect on Brix, ph, or TA for any of the berry samples, nor for the clusters at harvest (Table 1, Fig. 1). However, there was a significant effect of JB feeding on the ph of berry samples at one and two weeks before harvest as well as on the ph of the clusters at harvest. Vines that had a high level of JB feeding had fruit with significantly lower phs. Also, vines with that received high PLH and high JB feeding levels had slightly lower Brix levels at harvest, although this decrease was not significant. The results from the first year of this study indicate that grape vines can handle a lot of feeding damage by more than one pest early in the season, as evidenced by the lack of significant differences in shoot growth and cluster number and weight. However, the significant effects on some aspects of the fruit quality indicate that the vines ability to fully recover from damage from both pests appears to be limited. The second year of this study will provide more insight on these results as well as shed light on whether damage inflicted in the first year has an effect on vine health and fruit quality in the second year. Objective 2. Compare insecticides for their speed and duration of activity against PLH and JB. Potted Riesling grapes were treated with one of 13 insecticides or left untreated. Pots were left outside exposed to all weather except rain. Specific chemicals and rates applied are located in Tables 3 and 4. At 1, 3, 7, and 14 days after treatment (DAT) five PLH nymphs were held in place on the underside of treated leaves using a clip cage. Cages were left in place for 24 hours at which point nymphs were classified as alive, moribund, or dead. These insecticide trials were conducted in June 2012 and were repeated in July 2012 for JB. Instead of clip cages, Japanese beetles were placed in a 32 oz deli cup along with the treatment grape leaf in a water pick. After 48 hours the percentage of leaf area removed by beetle feeding was visually estimated in five percent increments. 2
Results from the PLH bioassays indicate that most of the insecticides provided excellent control through 14 DAT (Table 2). The only products that did not provide much control were Azera, Evergreen, and Pyganic. These chemicals showed slight efficacy at 1 DAT but no efficacy past that point. Results from the JB bioassays were similar to the PLH bioassays (Table 3). Most of the insecticides prevented JB feeding through the 14 days of the study. The organic treatments again had slightly lower amounts of JB feeding early on, but not later on in the study. The exception to this was Evergreen which reduced JB feeding on the leaves through 7 DAT. Objective 3. Develop and implement a thresholds-based canopy management strategy for Michigan winegrape growers. Based on our results from this first year of the study, in 2013 we will work closely with four growers whose farms are being visited weekly to develop a management plan that takes into account the potential of vines to tolerate feeding by these foliage-infesting insects. These sites will then be monitored weekly for insect pests, and we will plan to avoid insecticide applications for PLH and treat for JB once populations get to the point where significant defoliation begins to occur. COMMUNICATIONS ACTIVITIES, ACCOMPLISHMENTS, AND IMPACTS Publications Van Timmeren, S., Wise, J.C., and Isaacs, R. (2012) Soil application of neonicotinoid insecticides for control of insect pests in wine grape vineyards. Pest Management Science. 68: 537-542. Presentations Update on insect management in vineyards. South West Michigan Research and Extension Center. July 25, 2012. 80 attendees. Grape insect management using models and new insecticides. Three invited presentations in New York, Pennsylvania, and Ohio to National Grape Cooperative members. July 10-12, 2012. Total of 75 attendees. Integrating thresholds for leaf feeding pests into grape IPM programs. Isaacs, R. Ontario Fruit and Vegetable Convention. Niagara Falls, Canada. February 23, 2012. New insecticides and their fit for Michigan grape growers. Isaacs, R. Southwest Hort Days. Benton Harbor, Michigan. February 9 th 2012. Presentation slides available online: http://www.isaacslab.ent.msu.edu/extension_presentations.html FUNDING PARTNERSHIPS Funding from other projects from MGWIC and from US-EPA and chemical companies helped to support the technician working on this project. Acknowledgements We thank Pat Murad from the Dept. of Horticulture for fruit analysis and technical assistance with this project, and the farm management staff at TNRC as well as Delilah Clement, Emily Haas, Margie Lund, and Jacob Morden for technical help with this study. We also thank Doug Welsch for access to a site to collect insects, as well as the Michigan Grape and Wine Industry Council for financial support of this study. 3
Table 1. Brix, ph, and TA levels of Pinot gris grape clusters at harvest after exposure to low and high levels of potato leafhopper (PLH) and Japanese beetle (JB) feeding earlier in the2012 season. Means are presented ± SE. PLH JB Feeding Feedin Brix Level ph TA Level g Level Low Low 18.0 ± 0.5 3.7 ±.04 5.2 ± 0.2 Low High 16.6 ± 0.7 3.5 ±.03 5.6 ± 0.2 High Low 16.7 ± 0.6 3.6 ±.05 5.6 ± 0.3 High High 16.01 ± 0.6 3.5 ±.04 5.8 ± 0.2 4
Table 2. Percentage of PLH nymphs placed in clip cages on treated grape foliage that were moribund or dead after 24 hours. Nymphs were placed on treated foliage at 1, 3, 7, and 14 DAT. Percentages are presented ± SE. Treatment Rate per Acre 1 DAT 3 DAT 7 DAT 14 DAT Untreated NA 8.3 ± 8.3 20 ± 14.1 22.5 ± 10.3 26.3 ± 4.7 Actara 25WG 3.5 oz 100 ± 0 100 ± 0 100 ± 0 100 ± 0 Admire Pro 1.4 oz 91.7 ± 8.3 95.8 ± 4.2 100 ± 0 95 ± 5 Assail 30SG 2.5 oz 93.8 ± 6.3 100 ± 0 100 ± 0 96.9 ± 3.1 Azera 2 pints 57.1 ± 18.5 20 ± 11.5 53.8 ± 21.7 22.5 ± 9.0 Baythroid XL 3.2 oz 100 ± 0 100 ± 0 100 ± 0 100 ± 0 Belay 2.13EC 4 oz 100 ± 0 100 ± 0 100 ± 0 100 ± 0 Brigade 2.4EC 6.4 oz 100 ± 0 100 ± 0 100 ± 0 100 ± 0 Danitol 2.4EC 10.6 oz 93.8 ± 6.3 90 ± 10 76.3 ± 17.7 100 ± 0 Evergreen EC 60-6 16 oz 58.8 ± 19.6 25 ± 9.6 15 ± 5 17.5 ± 11.8 Hero 2.13EC 10.3 oz 100 ± 0 100 ± 0 100 ± 0 100 ± 0 Pyganic 1.4EC 32 oz 45 ± 15 23.3 ± 3.3 25.4 ± 12.6 25.7 ± 5.7 Scorpion 35SL 5 oz 100 ± 0 100 ± 0 95 ± 5 100 ± 0 Sevin XLR+ 2 quarts 95 ± 5 95 ± 5 100 ± 0 100 ± 0 5
Table 3. Average percent leaf area removed by JB feeding on treated grape foliage for 48 hours. Potted grape vines were treated with insecticides and individual leaves and beetles were put in deli cups at 1, 3, 7, and 14 DAT. Percentages are presented ± SE. Treatment Rate per Acre 1 DAT 3 DAT 7 DAT 14 DAT Untreated NA 53.8 ± 13.0 58.8 ± 5.2 65 ± 13.9 66.3 ± 6.9 Actara 25WG 3.5 oz 0.5 ± 0.3 13.8 ± 9.0 3 ± 1.1 2.8 ± 1.3 Admire Pro 1.4 oz 0.5 ± 0.3 1 ± 0 1 ± 0 0.3 ± 0.3 Assail 30SG 2.5 oz 0.3 ± 0.3 0.5 ± 0.3 2 ± 1 0.3 ± 0.3 Azera 2 pints 43.8 ± 15.6 37.5 ± 13.0 65 ± 13.2 47.5 ± 4.8 Baythroid XL 3.2 oz 0 ± 0 3.8 ± 3.8 0.3 ± 0.3 0.3 ± 0.3 Belay 2.13EC 4 oz 1 ± 0 0.3 ± 0.3 0.8 ± 0.3 1 ± 0 Brigade 2.4EC 6.4 oz 0.3 ± 0.3 0 ± 0 0 ± 0 0 ± 0 Danitol 2.4EC 10.6 oz 0 ± 0 0 ± 0 0.3 ± 0.3 0.3 ± 0.3 Evergreen EC 60-6 16 oz 18.8 ± 7.7 20 ± 6.5 32.5 ± 4.3 65 ± 8.7 Hero 2.13EC 10.3 oz 0 ± 0 0 ± 0 0 ± 0 0.3 ± 0.3 Pyganic 1.4EC 32 oz 50 ± 11.7 38.8 ± 4.3 80 ± 7.4 82.5 ± 4.8 Scorpion 35SL 5 oz 0.5 ± 0.3 0.8 ± 0.3 0.8 ± 0.3 0.5 ± 0.3 Sevin XLR+ 2 quarts 0.3 ± 0.3 0.5 ± 0.3 0.3 ± 0.3 0.5 ± 0.3 6
Figure 1. Brix, ph, and TA levels of Pinot gris berry samples taken at three, two, and one week prior to final harvest after exposure to low and high levels of potato leafhopper (PLH) and Japanese beetle (JB) feeding earlier in the2012 season. Means are presented ± SE. 7
Figure 2. Bioassay containers used for testing efficacy and residual effect of insecticides on potato leafhoppers (clip cage-top picture) and Japanese beetles (32 oz deli cup-bottom picture). 8