Disease

Frogeye leaf spot is one of the diseases growers should look out for, particularly among late-planted soybean plants. Photo courtesy of OSU College of Food, Agriculture and Environmental Sciences

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The Williams County Ohio State University Extension Office is keeping an eye on a couple of diseases and pests in the county while encouraging farmers to continue scouting fields as growing season continues.

Stephanie Karhoff, agriculture and natural resources educator for the Williams County OSU Extension, said producers should look out for leaf diseases in what few corn acres were planted this year.

“One of those is gray leaf spot and another one is northern corn leaf blight,” she said. “Those are two common ones to see in corn at this point.”

A third disease Karhoff said she is looking out for is tar spot.

Tar spot will leave small, black dots on the leaves that people won’t be able to remove with their fingers in the way they could with other pathogens.

“The reason we take note of it is because it’s newly emerging,” Karhoff said. “They’re trying to track the progress and also get an idea of how much effect it has on corn yield.”

She hasn’t heard of any incidences of tar spot this year in the county and it was only first reported in Ohio last year.

However, it has been seen in Michigan counties this year.

“Since we do border both Michigan and Indiana, it’s good to use us as a first line of defense or a frontline as far as keeping track of the progress of that pathogen,” Karhoff said.

The extension is also monitoring western bean cutworm.

This is a type of moth that will lay its eggs on corn leaf and the resulting caterpillars will feed on the corn plant.

“What we do is monitor for that pest by trapping the adult moths to get an idea of when the peak flight is and when is the best time to scout for those egg masses in the corn leaves and get an idea whether treatment should be taken or not,” Karhoff said.

The largest amount of moths found while monitoring was in the week of July 22, when they found 64 moths per trap. The week after there were only 20 moths.

“At this point, based on our tracking data, we’re past peak flight,” Karhoff said. “So, it’s not as much of a priority to scout for those egg masses, anymore, though it’s always a good idea to keep a lookout for that.”

For people with sweetcorn patches, she heard about an increase in corn ear worm in other counties.

This is a caterpillar with black, raised bumps and a spiny exterior that feasts on corn plants, Karhoff said.

She hasn’t heard much about diseases or pests in soybeans.

“It’s not as much of a problem, typically, in northern counties of Ohio but some southern counties are seeing what’s called frogeye leaf spot,” she said. “That’s a fungal disease.”

While it’s not seen much in these parts, it is something to watch out for.

The Extension is also researching soybean cyst nematode.

This nematode is easy to miss, Karhoff said, because it lives in the soil and feeds off a soybean plant’s roots.

“That one is the No. 1 soybean pest for Ohio,” she added. “A lot of times, you will have lower yielding fields and not realize it’s because of soybean cyst nematodes.”

Farmers interested in doing a soil test to find if their fields contain this pest can reach out to Karhoff at the Extension office.

The office is participating in a statewide study looking at numbers of the nematode in Ohio and how the current resistance works against the pest, she said.

“We can do the soil sampling and, what we do is, we’ll send the soil to a lab in Wooster or Columbus and they can do a test to see how many cysts are in that sample and also if it’s becoming resistant to some of the common varieties we use in soybeans,” Karhoff said.

At this point, the best thing a farmer can do with these diseases and pests is scouting and getting an idea of how much disease is actually in the field.

For many fungi, it is treatable, but it’s only economical at a certain level.

“If you do need to apply a treatment, keep in mind that timing that treatment is always important,” Karhoff said. “For corn, you’re going to see your best return if you’re treating that corn in tassel stage.”

She also recommends record keeping.

If a farmer is seeing a high level of a certain disease this year, it’s good to keep that in mind next year when choosing corn varieties, Karhoff said.

With the late planting and wet weather, it’s hard to judge whether it will be a bad year for these diseases and pests as there is no real comparable year to it.

“It’s always good to keep in mind what the weather pattern has been,” Karhoff said. “Some of these diseases like wet conditions, some of them like dryer conditions. So, keep in mind what kind of weather pattern we have. And, second, what resistance do you have in your corn hybrid or soybean variety.”

If a farmer has a hybrid that is particularly susceptible to a disease, then the fields with those hybrids should be prioritized.

This article originally ran on bryantimes.com.

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