Quantcast

Late season spraying

Wine Making Talk

Help Support Wine Making Talk:

Luvthepinot

Junior
Joined
Jan 5, 2014
Messages
12
Reaction score
4
Hello everybody I'm a long time reader, first time poster , and I'm in need of some advice. I have a small GSM vineyard ( 200 vines, 4 years old) in Northern CA. I'm having an issue with what looks like powdery mildew on the canes( dark splotches) and grapes covered in grayish powder . I have never sprayed because I thought it was unnecessary due to the excessive heat we get in our area ( routinely between 95 and 105 deg in the summer and harvest . What would be your advice at this point in the season ? At this point there is plenty of good fruit to make wine . I plan to harvest what's good in about a month . Thanks in advance for any advice ;)
 

jgmillr1

owner, winemaker
Joined
Jun 13, 2017
Messages
577
Reaction score
343
Presumably you are growing vinifera, given your vineyard location. That gives you the option of spraying sulfur on the vines for excellent powdery mildew control (not an option for those of us growing hybrid varietals!) Other likely more expensive sprays you can use are Rally, Pristine, etc. You'll have to carefully follow the labels for safety and PHI.
 

balatonwine

The Verecund Vigneron
Joined
May 9, 2017
Messages
968
Reaction score
665
Location
Badacsony wine region. Hungary
I have never sprayed because I thought it was unnecessary due to the excessive heat we get in our area ( routinely between 95 and 105 deg in the summer and harvest .
Temperatures above 100° F will effectively prevent development or spread of powdery mildew, but summer temperatures alone are actually not that relevant. Powdery mildew leaf infection can begin as early as bud break. Critical time for fruit infection is just before bloom until a month after bloom. You may not see symptoms of spring infection (especially on berries) until summer (i.e. now). Powdery mildew does well in moderate temperatures, while not requiring free water (i.e. rain) but just fog, dew or high humidity (such as at night) is enough: all which are possible environmental conditions in California in the spring and summer in many parts of the state.

What would be your advice at this point in the season ? At this point there is plenty of good fruit to make wine . I plan to harvest what's good in about a month .
If you live in California, your best resource is the University of California Integrated Pest Management (UC IPM) extension program:

http://ipm.ucanr.edu/PMG/r302100311.html

The above page also has a calculable index to help you know when you need to spray and when you do not.

Do NOT use sulfur now. Not only is it ineffective as a cure once the disease shows symptoms on a leaf or fruit, but sulfur can damage fruit and leaves when applied when days have high temperatures.
 
Last edited:

Luvthepinot

Junior
Joined
Jan 5, 2014
Messages
12
Reaction score
4
Thanks for the replies everyone :). It sounds like I need to spray after harvest in the fall, and begin a spray program next year after pruning and before bud break . Since I have an active infection now do I need to spray an eradicant like stylet oil this fall or would sulfur be adequate ?? Thanks again for the advice ;)
 

Latest posts

Top