Grape growers in the southeastern United States contend with two major pests, Japanese beetle (JB), Popillia japonica Newman, and green June beetle (GJB), Cotinis nitida L., that are absent or less troublesome in other grape-growing regions. JB severely defoliates vines, whereas both beetles feed upon and contaminate ripe fruits and are key pests close to harvest when spray restrictions limit management options. Grape cultivars adapted to the southern region vary in foliar characteristics and phenology of ripening in ways that likely affect resistance to both scarabs. Establishing vineyards with resistant cultivars should reduce vine loss and production costs, providing a quality crop with reduced chemical inputs. This project quantified costs of JB defoliation to growth, winter hardiness, berry development, and yield of vines of representative American, European, and hybrid cultivars maintained under conventional and reduced insecticidal regimes. In addition, phenological resistance, the use of cultivars that ripen before or after peak beetle flight, was shown to reduce or eliminate the need for fruit cover sprays close to harvest. Information gained from this project will help guide growers who favor organic or sustainable growing practices to cultivars that produce quality crops with minimal loss from the aforementioned scarab pests.
This project had two goals: to support field-based economic thresholds for JB defoliation of young grapevines, and to evaluate use of phenological resistance, i.e., planting of cultivars that ripen outside of peak periods of beetle activity, for alleviating Japanese beetle and green June beetle damage to ripe grapes close to harvest. Varietal resistance and the impact of JB defoliation on vine growth, fruit yield and quality has not previously been reported for planted vines, or for anything close to the severity of damage that occurs in KY.
The South has a long history of involvement with viticulture and enology. The Kentucky Vineyard Society, formed in 1789, was the first organization of its kind in the USA. By the mid 1800s North Carolina had become the largest, and Kentucky was the third-largest wine-producing state in the nation. Grape acreage in Tennessee in the late 1800s was 5–6 times greater than it is today. Although Prohibition resulted in the sharp decline of wineries, there is an ongoing resurgence in viticulture throughout the South. In Kentucky, where viticulture, especially a tourist-based winery-direct distribution model, is a promising agricultural alternative, most growers are new to the industry and either currently grow or until recently grew tobacco.
Cultivar choice and pest control are crucial to new growers due to the high cost of vineyard establishment and the fact that economic return may not occur for 3–4 years. The cost of re-establishing a failed planting could be devastating for small family owned farms. Most growers currently manage JB and GJB by weekly cover sprays. Registration of carbaryl, the most commonly used insecticide, is likely to be withdrawn. Label restrictions prohibit spraying most insecticides close to harvest which for many early and mid-season table and wine grape cultivars coincides with peak JB and GJB activity. Current recommendations (e.g., Midwest Grape Growers Guide 2008) provide relatively little information on sustainable or organic control options for JB and GJB.
This project contributed data to support economic thresholds for Japanese beetle which relatively recently has become a major grape pest in the Southeast. Such data have not been reported anywhere for planted vines. Our project quantified impact of JB defoliation on growth and winter hardiness of young vines, as well as tolerance differences among cultivar. It demonstrated that planting phenologically-resistant cultivars can reduce or eliminate need for cover sprays during veraison. This work supports best management practices for two key pests impacting the resurgent viticulture industry in the southeastern USA.
- 1.Support research-based economic thresholds for Japanese beetle (JB) defoliation of grapes by measuring impact of successive years of varying levels of defoliation on cordon growth, winter hardiness, berry development, and yield of American, European, and hybrid grape cultivars maintained under different intensity of cover sprays.
2.Evaluate phenological resistance, i.e., planting of grape cultivars that ripen outside of the window of peak pest activity, as a sustainable strategy for reducing Japanese beetle and green June beetle (GJB) injury to ripe fruit clusters close to harvest.
Objective 1: A research vineyard was established in May 2006 at the UK Horticulture Research Farm in Lexington, KY. The vineyard was planted in a 6 × 3 factorial design with two American (‘Concord’ and ‘Norton’), two European vinifera (‘Cabernet Franc’ and ‘Cabernet Sauvignon’), and two interspecific French-American hybrids (‘Chambourcin’ and ‘Frontenac’) maintained under three intensities of insect management and eight replications. Vines were trained to a single high-wire bilateral cordon system and managed according to University of Kentucky recommendations. Three insecticide treatments, carbaryl (label rate) applied every 7 or 14 d during the JB flight period, or no insecticide treatment, have been used for 2 years to provide varying levels of protection from JB defoliation. Standard JB traps and lures were used to monitor JB flight. Response variables evaluated included % defoliation, dormant pruning weights, fruit yield and quality for all cultivars, and LT50 (lethal temperature to kill 50% of the primary buds for Norton, Chambourcin, and Carbernet Sauvignon.
Objective 2: A second experimental vineyard consisting of six early-, mid-, and late-maturing cultivars planted in a randomized complete block was established at the UK Research Farm for use in evaluating the phenological resistance hypothesis. There are eight replications with duplicate vines planted per experimental unit. Cultivars and respective days to harvest were: Early-ripening: ‘Foch’ (90 d) & Jupiter (85 d); Mid-ripening: ‘Chancellor’ (100 d) & ‘St. Croix’ (99 d), Late-ripening: ‘Norton’ (125 d) & ‘Chambourcin’ (115 d). All have blue/black fruits to eliminate confounding effects of fruit color. The vines were protected from JB defoliation with carbaryl during the first two growing seasons. Vines were standardized to 60 grape clusters per vine (120 clusters per EU) in 2008. Weekly during GJB flight they were inspected in early afternoon and number of fruit clusters with JB and GJB feeding aggregations was recorded. Seasonal flight of GJB and JB flight were monitored using traps. Representative berries were sampled and analyzed for toughness (g) and sugars (% TSS) throughout the beetles’ flight period and concentration of total soluble solids was evaluated. In addition, representative grape clusters of each cultivar were harvested weekly for 3 weeks during peak beetle flight, confined with cohorts of 20 JB & 6 GJB, and screened for attractiveness to other beetles in the bait wells of large vane traps. Trap captures will be related to berry ripeness of the different cultivars as described above. Data were compared among early-, mid-, and late-season ripening cultivars by one-way ANOVA and planned single degree of freedom orthogonal contrasts.
Objective 1. Cultivars varied in susceptibility and response to defoliation by JB. Some (e.g., Norton) showed reduced vine growth, delayed post-veraison increase in total soluble sugars and pH, as well as reduced cluster number and weight, berries per cluster, and yield. Others (e.g., Concord) showed little or no measurable impact from JB. Norton and Chambourcin primary buds were more cold tolerant (i.e., had lower LT50) than Cabernet Sauvignon in both years. JB defoliation of non-sprayed vines significantly reduced cold-hardiness of all cultivars in one or both winters. Defoliation also reduced shoot length of first year vines, and may be associated with earlier termination of late season vine growth. This previously undocumented potential for JB injury to reduce winter hardiness of young grapevines exacerbates its role as a serious vineyard pest. For all vine response parameters, the biweekly spray regime was as effective as weekly sprays in mitigating the impacts of defoliation. Although defoliation from JB feeding can set back establishment and productivity of young grapevines, this work showed that growers can reduce spray frequency without compromising the benefits of JB management. Even susceptible cultivars can tolerate low to moderate (< 20%) levels of defoliation, and some are resistant enough to be grown without treating for JB.
Objective 2. GJB flight peaked in late July and early August coinciding with later stages of veraison of early-season ripening cultivars. Fruits of those cultivars recruited numerous GJB feeding aggregations resulting in > 95% crop loss. Small (1–2 wk) phenological differences between mid-season ripening cultivars and peak GJB flight translated to marked differences in injury, whereas cultivars that ripened in mid-August or later, after GJB flight had waned, sustained little or no damage. Berries of late-season ripening cultivars, which have relatively low sugar levels and tough berries during GJB flight, inhibited beetle feeding and induction of yeast-mediated volatiles and elicited little or no aggregational response. This work confirms that planting cultivars that ripen after peak beetle flight offers a viable management option for GJB. For growers choosing to produce earlier-ripening cultivars to expand production periods and target high-value market opportunities, this study should help them to predict which ones will suffer most from GJB and require the highest degree of protection. This knowledge will help new growers to better match their cultivar choice with their desired intensity of management, and help growers to focus GJB management where it is most needed. Understanding and exploiting ecological defenses of plants, including phenological resistance, is a sustainable approach that supports integrated pest management and organic agriculture production.
Educational & Outreach Activities
Hammons, D.L., S.K. Kurtural, M. Newman, and D.A. Potter. 2009. Invasive Japanese beetles facilitate aggregation and injury by a native scarab pest of fruits. Proceeding of the National Academy of Sciences (USA), 106: 3686-3691.
Hammons, D.L., S.K. Kurtural, and D.A. Potter. 2009. Phenological resistance of grapes to the green June beetle, an obligate fruit-eating scarab. Annals of Applied Biology 156: 271-279.
Hammons, D.L., S.K. Kurtural, and D.A. Potter. 2010. Impact of insecticide-manipulated defoliation by Japanese beetle (Popillia japonica) on grapevines from vineyard establishment through production. Pest Management Science 66: 565-571.
Hammons, D.L., S.K. Kurtural, and D.A. Potter. 2010. Japanese beetle defoliation reduces primary bud cold-hardiness during vineyard establishment. American Journal of Enology and Viticulture, 61: 130-134.
Hammons D.L., S.K. Kurtural, and D.A. Potter. 2009. Impact of Japanese beetle defoliation on first season crop yield and berry quality. 2009 Fruit and Vegetable Crops Research Report, PR-572, University of Kentucky.
Hammons D.L., S.K. Kurtural, and D.A. Potter. 2009. Phenological resistance of grapes to green June beetle damage. Ibid (see above)
Hammons, D.L., S.K. Kurtural, and D.A. Potter. 2008. Impact of Japanese beetle defoliation on the mid-winter bud hardiness of young grapevines. 2007 Fruit and Vegetable Crops Research Report, PR-555, University of Kentucky.
Scientific Presentations (oral)
Hammons, D.L., S.K. Kurtural, and D.A. Potter. Invasive Japanese beetles facilitate aggregation and injury by a native scarab pest of ripening fruits. Entomological Society of America National Meeting. December 2009.
Hammons, D.L., S.K. Kurtural, and D.A. Potter. Impact of Japanese beetle feeding on young grapevines. American Society for Enology and Viticulture National Meeting. June 2009.
Hammons, D.L. Insect-Plant Interactions and Sustainable Management of Japanese beetles and green June beetles in vineyards. Ph.D. exit seminar. Department of Entomology, University of Kentucky. March 2009.
Hammons, D.L., S.K. Kurtural, and D.A. Potter. Sustainable management for Japanese beetles in vineyards: Quantifying the impacts of defoliation. Entomological Society of America National Meeting. Symposium presentation. November 2008.
Potter, D.A., D.L. Hammons, S.K. Kurtural, and M. Newman. Sharks to a blood trail: Feeding-Induced and fermentation volatiles attract scarab beetles to grapes. Entomological Society of America National Meeting. Symposium presentation. November 2008.
Scientific Presentations (poster)
Hammons, D.L., S.K. Kurtural, and D.A. Potter. Phenological resistance of grapes to green June beetle damage. Entomological Society of America National Meeting. Poster Presentation. December 2009.
Hammons, D.L., S.K. Kurtural, and D.A. Potter. Phenological resistance of grapes to green June beetle damage. American Society for Enology and Viticulture National Meeting.
Hammons, D.L., S.K. Kurtural, and D.A. Potter. Sustainable management of Japanese beetles and green June beetles in Kentucky vineyards. Kentucky Fruit and Vegetable Conference. Kentucky Grape and Wine Short Course. January 2009.
Hammons, D.L., S.K. Kurtural, and D.A. Potter. Sustainable management and impact of Japanese beetles and green June beetles in Kentucky vineyards. Kentucky Fruit and Vegetable Conference. Kentucky Grape and Wine Short Course. January 2008.
Hammons, D.L. Biology and Management of Japanese beetles and green June beetles in grapes. Viticulture Summer Field Day, University of Kentucky. Lovers Leap Vineyards and Winery. August 2009.
Hammons, D.L. Japanese beetle and green June beetle management in grapes. Viticulture Summer Field Day, University of Kentucky. July 2008.
Hammons D.L. Impact of Japanese beetles and green June beetles in Kentucky vineyards, and sustainable management options. Horticulture Field Day and Twilight Tour, University of Kentucky. July 2008.