Paul Read,* Benjamin Loseke, and Stephen Gamet
*University of Nebraska – Lincoln, Plant Sciences Hall (PLSH) 377J, Lincoln, NE 68583 (pread1@unl.edu)

Declining yields in Nebraska vineyards and in the Midwest generally are variously attributed to vine aging, winter injury, or other environmental factors. Only recently have trunk diseases become suspect, largely because of concerns raised by Richard Smart in a June 2018 visit. A serendipitous opportunity arose for the University of Nebraska Viticulture Program (UNVP) to investigate trunk disease symptoms when a 20-year-old cultivar research planting was terminated in August 2018. This planting was on a commercial vineyard at Nebraska City, NE, and contained 36 cultivars, with the oldest vines planted in 1999. The vines were “destructively harvested” aboveground and evaluated for grapevine trunk disease (GTD) symptoms—a mini- mum of two replicates of 21 cultivars of hybrid grapevines, most of which had been in the ground for nearly 20 years. All were trained to a high-wire double cordon system. Evaluations were based on observations of both visible staining and dead wood symptoms found in cross-sections at five locations: 15 cm from the distal end of the cordon, at mid-cordon, at the juncture of the cordon and the trunk (crown), and at 90 cm and 10 cm aboveground on the trunk. All of the cultivars evaluated exhibited recognizable symptoms of TD, and some cross-sections also exhibited textbook symptoms of Eutypa and/or Botryosphaeria wedge-shape cankers. Severity of cross-section symptoms was rated on a scale of 1 (no visible symptoms) to 10 (cross-section completely stained or dead) using visual assessment.

Funding Support: Nebraska Grape and Wine Board