Project Number: 2034-21220-007-25-T
Project Type: Trust Fund Cooperative Agreement
Start Date: May 1, 2019
End Date: Apr 30, 2020
Objective 1: To evaluate efficacy of different fungicides to control Erysiphe necator on table grapes and to develop spray program with reduced risk of fungicide resistance development. Objective 2: Determine the distribution and development of fungicide resistant isolates on table grape.
Fungicide spray trial on table grapes to be conducted by University of California Cooperative Extension. ARS will collect bi-weekly samples of powdery mildew isolates for molecular testing of fungicide resistance and diversity. Powdery mildew isolates will be collected from grapevines tested with treatments 1 through 6 in 2019 and 2020. Isolates will be collected from symptomatic leaves every 1-2 wks from each treatment prior to fungicide application starting with the 30 cm shoot spray. Single colonies will be collected using a cotton swab or tough dot and placed into 1.5 mL microcentrifuge tubes. Approximately 30-100 colonies from each treatment will be collected depending on disease severity. Collected colonies will be returned to the lab for qPCR and sequencing analyses and storage.