Page 46 - Grapevine NovDec 2021

Around The VineyardThe Vineyard
Around

products get quite expensive. Explore lower-cost, Make applications during good spray conditions
effective options, and spray before the infection as indicated on the label, and avoid making applica-
becomes severe and widespread to help prevent tions when spray conditions are not good.
the need for expensive products.
• Effectiveness (efficacy) Looking Forward to the Winter
• What you have already applied this season
Managing mildews works best as a year-round
Many products have limits on the number of activity, but it doesn’t have to be overwhelming.
allowable applications each season, which are indi-
cated on the label. These limits are necessary to In the winter and early spring, remove dead and
slow the development of fungicide resistance. infected plant tissue that would otherwise create
new infections in the upcoming growing season.
Below are some suggested options for controlling
downy mildew and powdery mildew after harvest. One neat thing about growing grapes is that we
This is not an exhaustive list – consult your regional remove about 90% of the plant every winter and
spray guide for a full list. then grow up new, disease-free canes. That means
a lot of the diseased tissue goes away every year.
Downy Mildew To capitalize on this, many plant pathologists rec-
• Protectants – apply to prevent new infections: ommend removing and destroying all diseased
Captan (FRAC M4) and Mancozeb (FRAC M3) material from the vineyard instead of mowing it in
• Post-infection – apply to stop existing infections: the rows.
Phosphorus acids (FRAC 33). Phosphorus acid is
a common option for late season applications. Retraining new cordons and trunks is another way
Forum (FRAC 40) and Zampro (FRAC 40+45) also to manage diseases over time, because it removes
provide excellent control. disease spores that have accumulated on this
woody tissue.
Powdery Mildew
• Protectant – apply before infection: JMS stylet oil The importance of Sorting Infected Fruit
• Excellent control: Quintec (FRAC 13) and Torino
(FRAC U6) The computer science adage “garbage in, garbage
out” is a mantra that we should be sharing in the
Do not apply oils within 2 weeks of Captan or sul- wine world. Mildew can infect clusters, and grapes
fur application. infected with rots, mildews, or are otherwise
unsound (already fermenting) make faulty wines.
Rally (FRAC 3) can also be used for effective con-
trol of powdery mildew, but it does carry the risk Experiments have shown that wine made from
of fungicide resistance developing if you have been berries infected with powdery mildew could be
using it frequently already. distinguished due off aromas, flavors, and textures,
including ethyl acetate. These included flavors
Likewise, the strobilurins Pristine and Abound are described as moldy, bitter, dusty, plastic, and rot-
effective on downy mildew but have resistance risk. ten.

If you still have fruit to harvest, pay close atten- Using these key steps for mildew control is one
tion to the pre-harvest interval (PHI) on the product of many ways to help keep your vines healthy and
label. Phosphorus acid, Captan, and copper have wines delicious.
0-day PHIs, while many strobilurins have 14-day
PHIs. Mancozeb has a 66-day PHI, so it is only
appropriate for after harvest or very early in the
season.

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