Botrytis in grapes.

With CA grape harvest wrapped up, it’s important to look back at the 2019 season and evaluate what worked, and what didn’t. A recap of the season helps plan future crop management, and can prepare you for 2020. We talked with agronomists Garrett Gilcrease and Don Lewis, who shared what they’ve seen in grape vineyards this season, and what to plan for moving forward.

What were the most damaging insects and diseases in grapes this year?

The primary insect that people are scouting is a pest called mealybug. That’s the insect we battle the most in northern CA.

The disease we face most often early in the season is Phomopsis, which is usually the first disease of the season we get called in to help control. This is typically followed by powdery mildew, which is spotted early and mid-season in cooler, wetter climates. Many areas face late-season botrytis, and the final disease is sour rot, which is seen a month or so before harvest.

What products and solutions best control these issues?

For mealybugs, we recommend an application of Platinum® insecticide, which offers residual control of sucking and chewing insects.

For disease control, we have a few recommendations. When dealing with Phomopsis and early powdery mildew, we suggest Quadris® Top, an extremely versatile fungicide. For mid-to-late season powdery mildew and botrytis, an application of Inspire® Super or Vanguard® WG fungicides can provide long-lasting control. As we approach harvest, the sour rot disease complex can cause yield losses. That’s where a product like Switch® 62.5WG fungicide comes in, as it is extremely strong on the botrytis and sour rot complexes. We anticipate having another fungicide to use against powdery mildew and botrytis available to CA growers for the 2020 season.  

What are some additional management tips for 2020?

For grape disease control, some areas can see as high as 8-12 product applications per year. The biggest factor with disease is that you can never get behind. If you allow disease to get a foothold, there’s no amount of product you can put on it that can bring that crop back. You have to get ahead and make sure you are introducing timely applications.

For more insight into your grape vineyards and how to manage disease and insect pressure, contact your Syngenta representative.

Sign up for the Know More, Grow More Digest to receive twice-monthly agronomic e-mail updates pertinent to your area.

All photos are either the property of Syngenta or are used with permission.