What is in this article?:
- Frogeye leafspot fungus resistance to strobilurin chemistry a concern for Mid-South soybean growers
- Southern corn rust widespread in 2010
- Aerial web blight found in several areas
Add another to the growing list of weeds, insects, and diseases that have developed resistance to the chemicals that farmers rely on to control pests and protect yields — strobilurin-resistant Cercospora sojina, the fungus that causes frogeye leafspot in soybeans.
Southern corn rust widespread in 2010
There was “a phenomenal outbreak of southern corn rust across the Mid-South and South,” last year, Allen says. “We hadn’t previously seen that much southern corn rust in early June.”
One of the reasons behind the spread of the disease, he notes, is that farmers in Mexico are growing more corn in areas where it hasn’t traditionally been grown. “This likely is a factor in a great deal of our southern corn rust, common rust, and rust situations in other crops.”
None of the rusts overwinter in the U.S., he says, except for a little soybean rust. “If we have rust in our fields, whether it be corn or even wheat, it has to blow in from somewhere else, like Mexico.
“We had a lot of questions from growers about southern corn rust last year, particularly if it would result in lodging, and how they could address that concern.
“For years, we’ve said that, based on previous research, applying foliar fungicides two weeks prior to black layer would likely not provide an economic return in most years. But in a year like 2010, with high levels of southern corn rust and a prolonged conducive environment, fungicides made a difference.”
In a field trial at Stoneville, Allen says, corn treated with 6 ounces of Headline fungicide outperformed all other treatments, including other strobilurin and triazole chemistries.
“Are we ever likely to see that much southern corn rust again? Maybe. Will we see it in 2011? Probably not.
Was there any lodging as a result of the disease in my trials? Essentially, no.
“Is your corn going to fall over if you get southern corn rust at a high level? Possibly, but that would be more likely if high levels of infection occur earlier in the season. With late-planted corn, you may have to manage southern corn rust with more than one fungicide application — this is one reason corn following wheat is such a difficult sell.”