Experts Urge Proper Sanitation to Prevent Wheat Weevil Problems

11/2/2013 7:00 AM
By Amy Halloran New York Correspondent

"Of all the grains we have, wheat is the most susceptible to insect injury," said Mike Stanyard, regional field specialist with Cornell’s Northwest New York Dairy, Livestock and Field Crops Team.

Reports of wheat being rejected due to weevil infestation prompted him to write a brief notice in the September “Crop Alert” on handling this problem.

"We had a wheat grower who had some weevils in their wheat bin," said Mike Hunter of Lewis County Cooperative Extension. "When he found them, he was at a loss because he's not a certified pesticide applicator in New York state. He needed to make the treatment in the bin, but there are only 12 people certified in the state and no one was close to the location."

Once weevils settle into a bin, fumigation is the protocol for conventional crops. Another treatment option, using aluminum phosphide tablets or pellets, was not available to the grower either because its use requires a private pesticide applicator license.

The “Crop Alert” recommended treating empty bins prior to harvest with products such as Tempo SC and Storcide II for long-term storage of wheat. Since treatment is so difficult, prevention is the best cure for this and other insect problems in stored grains.

"I think it comes down to sanitation," said Stanyard. "Sanitation is key.”

On a recent farm visit, he got into a bin, closed the door and looked for holes in vents. He pointed out the little holes in the ladder that can get packed full of grain and found that the farmer hadn't cleaned where the motor is, or behind the fan.

"I walk people through that grain bin and say here's the little hiding spots," he said.

"I never put new grain on top of old," said organic grain farmer Thor Oechsner. "We go in the bins and use compressed air to sweep the walls. I have a bottle brush on a stick to clean the little holes in the ladder rungs. Everything gets vacuumed, and we get it as clean as we can."

If there is an insect problem, organic farmers can use an OMRI-approved product to fog the bin, or diatomaceous earth. Letting a bin go empty a year can be helpful, too.

Some people say there were more weevils in their wheat this year, causing some to speculate as to why.

"Did it go in from the field directly into the bin?" Stanyard said. "That's hearsay. I don't have a way of proving it. Growers feel that maybe the weevils actually got in the wheat in the head stage."

If that is the case, it might explain why weevils got established so quickly this year. However, two operations, SeedWay in Hall, N.Y., and Star of the West Milling in Churchville, N.Y., said they are not seeing more weevils.

"This time of year we generally don't see weevils in incoming wheat, not when it's coming right out of the field," said Francois Lachance from Star of the West. "Usually we'd see them when grain has been in the bin for a period of time. More often we see grain weevils in winter or spring, but not at harvest. This year I don't think we've rejected a single load for grain weevil."

The mill has accepted more than 1 million bushels since harvest started.

"Grain weevils bore into the wheat kernel," said Lachance, which he said creates an environment condusive to damage from other critters such as the flour beetle, which can't bore through the bran coat itself, but is attracted to the fines or dust.

Cleaning grain prior to storage is a good management technique.

"Everything goes through a rotary cleaner," said Oechsner of his routine. "The less fines and broken kernels you have, the less problems you have."

Heather Darby of University of Vermont Extension recommends this strategy as well.

"Make sure seed is clean and dry and check regularly for hot spots," said Darby. "Moisture can draw in insects."

Pest traps on the farm and in bins help to monitor and sometimes reduce populations. Heating grain to high temperatures to kill pests, she said, is another alternative for organic farmers. Once the pests are killed, the grain should be put through a cleaner.

Temperature is a great tool for trying to keep grains more free from problems.

"Let's face it, we need to have a cold, hard winter," said Steve Treleaven, operations manager at SeedWay.

He hasn’t seen a large weevil presence thus far. This is likely due to growers pretreating bins prior to storage. Even though people are proactive in terms of pest control, a real winter would be a plus.

"This would really help out with the insect pressures that people might be seeing," he said. "We haven't seen enough subzero or single digits to say so in the last two years. Homeowners are seeing more fleas and ticks on pets, and more mosquitoes. We need to get back to having a good old-fashioned winter."

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