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Results Mixed When Fungicides Applied To Healthy Corn

Spraying healthy corn plants with the fungicide Headline to boost yields most often didn’t pay in trials conducted in North Dakota and Manitoba last year.

Moreover, excessive use of the fungicide (a strobulrin), which controls disease through just one site of action, could speed up disease resistance to the chemical, Joel Ransom, an extension agronomist at North Dakota State University in Fargo told the Manitoba Special Crops Symposium in Winnipeg Feb. 11.

“We saw one location (out of three in North Dakota) where we had a statistically significant increase and it was about nine bushels (an acre),” he said. “The other numerical increases were minor and not statistically significant.”

Based on US$4 a bushel corn and US$24 an acre to apply Headline, a farmer needs a yield increase of six bushels an acre to break even on the application, Ransom said. The higher the price of corn, the more economic the treatment becomes.

Tests conducted near Carman in 2008 showed no yield difference between corn sprayed with a half or full rate of Headline and untreated corn, he said.

BASF, which makes Headline, is testing the “plant health” benefits of treating healthy corn with Headline. In 2007, BASF found the treatment boosted corn yields at 26 Manitoba sites by an average of 6.05 bushels an acre, Robert Hornford, BASF’s senior technical development representative for oilseeds and pulse crops told the annual special crops tour last July 23.

Applying Headline improves plant health by reducing stress, improving photosynthesis and keeping leaves from dropping prematurely resulting in a bigger, higher-yielding plant, Hornford explained in an interview.

Anytime a corn leaf is subjected to physical damage from wind or hail or a disease the plant emits the hormone ethylene, which causes leaves to fall off the plant earlier than if they were healthy. Headline blocks the ethylene.

“It keeps these leaves on longer, which lets you build a bigger plant,” Hornford said.

“Plant health is sort of a new trend – trying to get more bushels out of the same acre by using some products that have more than their herbicidal or fungicidal activity.”

Ransom said he reviewed other trial data from 137 locations in the United States and Ontario. At one location the treatment boosted yields by 40 bushels an acre, but at another it reduced yields by 20 bushels an acre.

“If we took the average we got a 3.6-bushel yield increase,” Ransom said. “On average it didn’t pay to put fungicide on corn in 2008. Obviously there were some locations where it was highly profitable and some where we actually lost money.”

What Ransom found in the trials outside of the northern U. S. and Manitoba, was that the higher the incidence of disease in the corn, the better the yield response to spraying with Headline. Where the severity was rated five per cent or less, spraying boosted the yield by just 1.2 bushels an acre.

“So if there is no disease (there is a) fairly low response,” he said.

When the disease severity was rated greater than 10 per cent, yields of the treated corn jumped 10 bushels an acre. Where the rating was more than 25 per cent yields went up 12.7 per cent when treated, but that only occurred at six out of the 137 sites.

Ransom suspects corn treated with Headline in North Dakota and Manitoba isn’t responding because it’s relatively disease free. The fact that corn hybrids grown here don’t yield as much as those in warmer areas could be another factor, he said.

Ransom said according to Pioneer Hybrid studies in the U. S. and Ontario, spraying corn with Headline last year was economic 52 and 41 per cent of the time, respectively.

“I’m not a gambler,” he said. “I don’t know if those are good odds or not. They are better than slot machines, but not a lot better.

“And given the limited response to fungicides in North Dakota, Minnesota and Canada the risk of not obtaining a return to the cost is moderately high. I’m not saying you can’t get a return, I’m just saying that there is some risk if you put money out you won’t get a return on it.”

There’s also evidence that spraying corn with Headline before tasseling can injure the crop resulting in reduced yields. The damage is caused mainly by the surfactant in the mixture.

Ransom said some research suggests applying Headline to corn does boost plant growth and yield.

“The data I showed you would suggest most of the positive effects can be attributed to (controlling) the disease, but we still have more basic research to do,” he [email protected]

About the author

Reporter

Allan Dawson

Allan Dawson is a reporter with the Manitoba Co-operator based near Miami, Man. Covering agriculture since 1980, Dawson has spent most of his career with the Co-operator except for several years with Farmers’ Independent Weekly and before that a Morden-Winkler area radio station.

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