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Friday, September 2, 2016

Keeping critters away from your sweet corn

Green laser lights may be the answer

Professor Rebecca Brown poses in the URI agronomy fields where she is testing various strategies for keeping birds from feeding on sweet corn. (Photo by Nora Lewis)
Professor Rebecca Brown poses in the URI agronomy fields
where she is testing various strategies for keeping birds from
feeding on sweet corn. (Photo by Nora Lewis)
Large flocks of starlings and blackbirds are voracious consumers of sweet corn, costing local farmers as much as $800 per acre in lost product. And this year is turning out to be a particularly bad year for bird damage.

But the most effective and economical strategy farmers have used to scare the birds away – propane-powered cannons that make a loud booming sound at random intervals – are not especially popular with neighbors, many of whom complain about the noise. 

So the Rhode Island Department of Environmental Management asked a University of Rhode Island researcher to investigate alternatives.

Rebecca Brown, a URI professor of plant sciences and an expert on growing vegetables, said the problem of bird damage in commercial corn fields is a serious one.

“Flocking birds can cause an enormous amount of damage to sweet corn,” she said. “They get in there and shred the husks and eat the kernels, and then the farmers can’t sell it. Some birds have even figured out that if they follow the picking crews, they’ll get the best corn at the best time.”

In addition to propane cannons, some farmers have tried tying reflective tape or balloons throughout their fields to frighten the birds or used spray-on bird repellents. But neither is cost effective.

So Brown began by investigating a practice called topping, which some advocates claim is effective. The practice involves cutting off the top of the plant after it sheds its pollen.

“The idea is that it stops the birds from damaging the corn because it significantly reduces the amount of cover they have in the fields,” Brown explained. “So instead of having five or six leaves over the bird while it’s sitting on an ear and eating, there’s only one. It supposedly makes the birds more vulnerable to hawks and other predators, reducing damage to the corn.”

But it doesn’t appear to be the answer farmers were hoping. While Brown has little data suggesting that the practice is effective at reducing damage, her studies found that it reduces the yield of corn from each acre while requiring a great deal of labor – or a very expensive and specialized tractor – to implement.

“That added cost and reduced yield, which also means a reduced income, means it’s not worthwhile,” Brown said.

Next Brown turned to the use of green lasers in place of cannons to scare the birds. She built a prototype using a commercial laser pointer for less than $200 that she hooked to a digital module and programmed to shine the light beam across the field in different patterns. 

So far, it seems to be working, and it doesn’t harm the birds.

“Birds are much more sensitive to green light than we are,” she said. “So even if you can’t see the light beam, the birds can. And birds are particularly sensitive to moving light. Their chief predator comes after them from above. So when they see that flash of light, the birds wonder whether it’s just a flash of light or a hawk. They don’t want to stick around to find out, so they clear out.”

Some commercial growers of sweet corn in Rhode Island have purchased high-powered laser systems for as much as $2,600 that can cover an area of 15 acres, and Brown said they are happy with the results.

“I’m still trying to get data on how effectively it keeps the birds away, but it looks promising,” Brown said. “One of the hard parts of getting data is that the growers want to protect all of their corn, so getting them to do a control plot with no protection is difficult.”

She plans to conduct one more year of tests using a green laser to confirm the results of this year’s preliminary study.

“I had never heard of anyone using a laser before late last summer, so this has been our first preliminary study,” Brown said. “Hopefully next year we’ll be able to say that we’ve solved the problem.”