TY - JOUR T1 - Phenology-Dependent Effects of Foliar Injury and Herbivory on the Growth and Photosynthetic Capacity of Nonbearing <em>Vitis labrusca</em> (Linnaeus) var. Niagara JF - American Journal of Enology and Viticulture JO - Am J Enol Vitic. SP - 252 LP - 260 DO - 10.5344/ajev.2003.54.4.252 VL - 54 IS - 4 AU - Rodrigo J. Mercader AU - Rufus Isaacs Y1 - 2003/01/01 UR - http://www.ajevonline.org/content/54/4/252.abstract N2 - The response of potted fruitless Vitis labrusca (L.) var. Niagara grapevines to early and late season mechanical and insect defoliation was recorded. Twenty percent of the leaf area was removed with a hole puncher to simulate insect injury early and/or late in the season. Measurements of growth, single-leaf photosynthesis, and whole-vine photosynthesis indicated a higher tolerance to foliar injury late in the season than early in the season. Because defoliation was made on a percentage basis, the results were due to the stage of vine development at the time of damage rather than to the amount of leaf area injured. In a second experiment, measurements of vines injured early in the season by the rose chafer, Macrodactylus subspinosus (F.), and late in the season by the Japanese beetle, Popillia japonica (N.), indicated qualitatively similar impacts of beetle feeding on growth parameters compared to vines injured mechanically. Feeding injury by the Japanese beetle had a negative impact on whole-vine carbon assimilation not observed in mechanically injured vines. A final experiment comparing the effect of mechanical and beetle injury early and late in the season on single leaves indicated no significant differences between rose chafer and mechanical injury early in the season. However, 17 days after injury, leaves injured late in the season by the Japanese beetle had lower carbon assimilation rates than mechanically injured leaves. This response was detected on both injured and uninjured sections of injured leaves.Acknowledgments: The authors thank Ashley Grieves, Anna Neiss, and Kasey Watts for their work on this project and Keith Mason for his technical assistance. The authors also thank G.S. Howell for valuable advice on viticultural techniques and concepts. Partial funding for this project came from the Viticulture Consortium-East program through a subcontract with Cornell University, NYSAES, Project GREEEN, and the Michigan Agricultural Experiment Station. This research was in partial fulfillment of the MS degree for RJM. Research was conducted at the Michigan State University Center for Integrated Plant Systems greenhouse facilities. ER -