Phenophase-Dependent Growth Responses to Foliar Injury in Vitis labruscana Bailey var. Niagara during Vineyard Establishment

¹ Department of Entomology, 243 Natural Sciences Building, Michigan State University, East Lansing, MI 48824.

Email: isaacsr{at}msu.edu

In comparison to mature vines, the lack of fruit and lower carbohydrate reserves in vines during establishment create a situation in which the lowest source to sink ratios occur early in the season during rapid vegetative growth. This study compared responses of young Vitis labruscana Bailey var. Niagara vines to injury applied early in the season (bloom) and/or late in the season (veraison). Different sets of plants were injured with hole punchers to imitate foliar injury by leaf-skeletonizing beetles either during bloom, during veraison, or during both phenophases in 2000 and 2001, using a 2 x 2 factorial design. In 2000, vines were injured during bloom by removing 30% of the total leaf area of each fully expanded leaf and during veraison by removing 30% of the subsequently expanded leaves on 1.5 m of each shoot. During 2001, injury during bloom and veraison consisted of removing 20% of the total leaf area of all fully expanded leaves, thereby removing the same percentage of the source available each time. Injury applied during bloom in 2000 significantly reduced pruning weights, total shoot length, and cane diameters the following season, while veraison injury did not. Vines injured during bloom in 2001 had lower numbers of nodes and mature nodes, lower pruning weights, and lower total cluster weight the following season compared to the uninjured vines, while vines injured solely during veraison showed no significant response to injury. In both years, vines injured during both bloom and veraison had the greatest reduction in vegetative growth. Results indicate that during the establishment phase vines are more tolerant of injury during veraison than during bloom and that foliar injury early in the season can significantly reduce a vine's ability to tolerate subsequent foliar injury.

Note:
Acknowledgments: Funding for the project was provided by Project GREEEN, The Viticulture Consortium-East through a subcontract with NYSAES, Cornell University and the Michigan Agricultural Experiment Station. This research was in partial fulfillment of the MS degree for RJM. Our thanks to Bruce Van Den Bosch, Jason Keeler, Kasey Watts, and Kelly Bahns for their work on this project, to Keith Mason for technical assistance, and to all the members of the Small Fruit Entomology laboratory at MSU for their help with mechanical injury treatments. We are grateful to John Wise and the staff at the Trevor Nichols Research Complex for providing vineyard management services and research facilities. We also thank G.S. Howell for valuable advice on viticultural techniques and concepts.

Key words: tolerance, source to sink ratio, herbivory, defoliation