Final Report: This is year 3 of a 3 year project for the Washington Grape & Wine Research Program
Date: February 20, 2014

Project Title: Systems-Based Management of Powdery Mildew and Botrytis Bunch Rot of Wine Grapes (continuation from 2011 and 2012)

Principal Investigator(s): Gary Grove (objectives 1-5) and Michelle Moyer (objectives 1-2)

I. Project Summary: This work is focused on the effect of duration of berry wetness and temperature on the infection of wine grapes by B. cinerea in Eastern Washington. Field studies were conducted to evaluate whether the current Washington State University AgWeatherNet Bunch Rot model is compatible with typical weather conditions in Eastern Washington. Tests were performed post-veraison 2011-2013 and during bloom in 2013. The data suggests the currently available predictive model may be under predictive, especially in vineyards with diffuse powdery mildew infections. Four fungicides were also evaluated post-infectively to determine how much time post wetting period/inoculation could elapse and still allow for good protection of flowers and clusters. Results showed that some fungicides might effectively control Botrytis 48-hours post infection of berries. The economic viability of this approach is unclear.

II. Materials, Methods and Experiments Conducted to Meet Stated Objective(s):

  1. Develop bio rational and sustainable PM (PM) fungicide programs through the judicious application of various fungicide modes of action in conventional and organic, bloomcentered fungicide programs. Efforts were focused on the period before berries develop ontogenic (age related) resistance to PM. Some disease management approaches were evaluated for efficacy against PM and effects on insect populations.
  2. Evaluate organic and conventional programs for control of PM on clusters and develop cost-effective leaf removal/fungicide programs for disease management. The latter portion of this objective is part of proposal “Horticultural Impacts of Fruit Zone Leaf Removal in Wine Grapes and Mitigating Botrytis Bunch Rot in the Winery” (M. Moyer, lead PI). Synthetic and organic trials were conducted to evaluate the efficacy multiple fungicide regimens for management of grape powdery mildew. Fungicide applications were made to mature ‘Chardonnay’ or ‘White Riesling’ vines located at the Washington State University Irrigated Agriculture Research and Extension Center, Prosser, WA. Powdery mildew incidence and severity were rated on fruit clusters by visually determining the percent cluster area with powdery mildew on 24 arbitrarily selected clusters per plot (12 from the west and 12 from the east side of each plot). On 17 Aug disease incidence and severity was rated on leaves by visually determining the percent leaf area with signs of the disease on 80 arbitrarily selected leaves per plot (40 from the west and 40 from the east side of each plot).

Read more by downloading the full report above.

Pest & Disease // Sustainability //