Every year, corn and soybean growers begin with a detailed plan derived from past experience and expert advice from retailers and agronomists. However, even with a solid plan in place, growers must often adjust to curveballs thrown by Mother Nature. That hasn’t changed with this current growing season. Many farmers agree that uncontrollable weather events disrupted their best laid plans more than ever this year.
Eric Tedford, technical fungicide lead with Syngenta, explains: “2019 has been anything but typical with historic levels of flooding and extreme weather across the Midwest. As a result, many growers faced severely delayed planting, which means higher disease pressure at key reproductive — yield-establishing — growth stages. This means diseases that normally come in later in the season will have a greater impact on yield potential this year than in previous years.”
Also, late-planted crops are at greater risk because they are exposed for a longer period to higher populations of spores from overwintering foliar diseases, such as tar spot, northern corn leaf blight and gray leaf spot in corn. In soybeans, it’s frogeye leaf spot and brown spot, while the crop is growing to full maturity. And diseases like southern rust that normally don’t overwinter in the Midwest have more time to blow in and infect vulnerable plants.
Corn foliar diseases
In corn, here are three key foliar diseases to watch for:
- Gray leaf spot. It develops thin rectangular lesions along the leaf veins that combine together into longer lesions as the disease progresses.
- Northern corn leaf blight. This disease causes long elliptical (cigar-shaped) lesions on plant leaves. Lesions first appear grayish-green but soon turn ashy gray.
- Tar spot. It produces tar-like spots splattered across the leaf surface. These spots are difficult to scrape off.
Soybean foliar diseases
In soybeans, these two foliar diseases often show up:
- Frogeye leaf spot. This disease causes small irregular circles that develop into brown spots with reddish-brown rings on the outside.
- Brown spot. It ultimately produces small, dark brown lesions in irregular shapes. Infected leaves will turn yellow and drop off.
It’s not too late to preserve yield potential, Tedford says. The right fungicide application in corn or soybeans can still help reduce the impact of foliar diseases and give crops a much-needed boost with plant-health benefits.
“Many growers are likely considering skipping a fungicide due to the difficult season they’ve faced already, but there’s still opportunity to maximize yield and get the most out of a fungicide application. In any plant, the less energy it uses to fight diseases, the more energy and time it has to bulk up yield,” he says.
Tedford recommends Trivapro or Miravis Neo fungicides applied at VT/R1 growth stage for corn and R2-R3 growth stage for soybeans.
“Both products encourage plant health and provide excellent control of the most difficult and yield-reducing foliar corn and soybean diseases,” Tedford says. “As we get deeper into the summer, diseases are going to crop up quickly, and having a product you can trust with broad-spectrum, long-lasting control will be key to stopping many of the diseases Mother Nature may throw your way.”