Leaf spot presented many challenges to Virginia peanut farmers in 2018 thanks to rainy weather and wet conditions throughout much of the growing season. Farmers need to be on the lookout for the disease this year.
Speaking at the Virginia peanut production meeting at the Paul D. Camp Community College Workforce Center in Franklin, Dr. Hillary Mehl, Virginia Tech Extension plant pathologist, stressed the importance of timely applications to control leaf spot.
“Once you delay your application, the leaf spot begins to get away from you and you’ll see high levels of leaf spot. We saw poor leaf spot control in Virginia in some situations in 2018,” Mehl said.
Farmers can either used a calendar-based approach or the Virginia Leaf Spot Advisory program to manage their fungicide applications, Mehl said. If weather conditions are favorable for leaf spot this year, Mehl said Virginia peanut farmers may need to switch from a four-spray program to a five-spray program
“With the weather we’ve been having, it’s been worse for leaf spot epidemics. We’ve had a harder time controlling leaf spot. There’s not as much ability to be off on your spray timing and still get good control. The Leaf Spot Advisory in 2018 recommended sprays approximately every two weeks, whereas in some years we had periods of low risk which made it so we could stretch out those intervals to three weeks, sometimes more,” Mehl said.
To control leaf spot, Mehl stresses:
- Early sprays are important.
- Rotate modes of action, active ingredients.
- Mix modes of action, active ingredients.
- Include fungicides for soil-borne diseases in leaf spot programs.
Mehl said there are new products available that can be incorporated into programs and perhaps improve leaf spot control. Last year, Miravis fungicide from Syngenta became legally available in Virginia to control leaf spot in peanuts. Mehll said Miravis is excellent for controlling leaf spot but does not control stem rot, which can be a problem in a lot of Virginia peanut fields.
“If you use Miravis, it is excellent for leaf spot control, but you need to include a product in your fungicide program that will control stem rot. This disease is more and more common,” she said.
“Early sprays are probably where Miravis is going to fit best in your program. It’s an expensive product. Most likely, you’re only going to want to make one application of Miravis,” she added.
In addition, there is a new formulation of Provost from Bayer called Provost Silver that is expected to be labeled for leaf spot in Virginia this season. Provost Silver is already labeled for leaf spot control in North Carolina and South Carolina. Mehl said Provost is also effective for stem rot control.
Also, Mehl said there is a supplemental label for Domark in Virginia peanuts this year. She said Domark is primarily used for leaf spot control and should be mixed with other fungicides such as Bravo and rotated with other products
Finally, Mehl said if Sclerotnia blight is an issue, an application of Omega or Endura may be needed. These products will also provide some leaf spot control.
“You need to make sure you’re adjusting to what diseases you have in your field and how confident you are in your fungicide program to control all of them in order to maximize yield. Since we have a spectrum of diseases we’re trying to control, we want a spectrum of fungicide activities,” she said.
Working around wet weather is a challenge.
“Potentially, the calendar-based sprays are easier because you know when you need to get out. You can look at the weather forecast and plan ahead and incorporate your sprays around those weather events,” Mehl said. “The Advisory I think is reliable. We’ve had increased risk this past year and increased leaf spot severity and our advisory really reflected that with more recommended sprays.”