Minimizing Spray Programs for Control of Grape Disease Based on Phenological Stages of Susceptibility 1997
Project Leader: Wayne Wilcox
1. Determine the optimum timing and minimum number of sprays to reliably control black rot.
2. Determine whether two fungicide sprays applied immediately before bloom and 2 wk later can provide acceptable commercial control of powdery mildew on 'Concord' fruit if good spray coverage is obtained.
3. Determine whether a program of MKP and a DMI fungicide can provide acceptable control of powdery mildew on a highly susceptible grape cultivar, by targeting a the DMI during the period of maximum fruit susceptibility.
The critical sprays for the management of black rot were the one applied at immediate prebloom and the first two applied postbloom. If these three were applied, all other sprays were superfluous. Similarly, the critical sprays for the management of powdery mildew were those applied from bloom through fruit set. Although later fungicide sprays can still be beneficial (particularly for the grape foliage), they appear to be much less critical and might be replaced with alternative control measures. Midsummer applications of the fertilizer monopotassium phosphate to plant leaves were as effective as standard fungicides when integrated into a program using conventional fungicides in the critical fruit-set period beforehand.