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Do Late Planted Soybeans Need Fungicides?

Do Late Planted Soybeans Need Fungicides?
It's not too late to apply fungicide on soybeans, particularly on the later-planted fields, experts say.

Some farmers with late planted beans are asking: Is it too late to spray a foliar fungicide on soybeans, particularly on the later-planted fields? Plant disease specialists say, although the calendar is now moving into mid-August, it's not too late. Many of the late planted beans this year are just now getting to the R3 growth stage, they note. The Iowa Soybean Association's On-Farm Network replicated strip trials over the past few years suggest that fungicides do pay.

However, this is not a typical year. Some of the growers who've participated before in fungicide trials have been hesitant to put out trials on late-planted beans this year. Why are they hesitant?

IS DISEASE PRESENT? Before spraying a foliar fungicide on soybeans, it's important to scout and determine the type of disease or diseases present in a field, say ISU plant pathologists. Only fungal pathogens can be controlled with these products. Scouting should be done prior to the R3 growth stage of the soybean plants, especially if weather has been rainy and/or humid. These conditions favor foliar diseases.

"We know that in years with conditions conducive to disease development, fungicides will likely increase yield by 2 or 3 bushels per acre," says Tristan Mueller, the On-Farm Network's operations manager. "Besides increasing yield though, keep in mind that fungicide application, in some cases, delays drydown of stems and beans. In On-Farm Network trials, foliar fungicide application has increased soybean moisture at harvest by an average of about 0.1%. In most years, a slight increase in moisture isn't much of a price to pay for a few more bushels per acre."

ISU research shows fungicides increase yields on beans planted from April through early June

Data from planting timing trials conducted by Iowa State University Extension plant pathologist Daren Mueller and ISU research farm manager Ken Pecinovsky between 2009 and 2012  shows fungicides increase yields on beans planted from early April through early June. "For soybeans that went in on time, or even three to four weeks late, applying fungicides still seems to be a good idea," Mueller says.~~~PAGE_BREAK_HERE~~~

"But some of the later planted beans this year weren't in the ground until after the first of July. That's a month later than the latest planted beans in the Iowa State University study," he points out. "Since we know those beans are going to mature late, there is a chance for greener stems and a little more moisture in the beans. Given the fact that we can't predict when the first frost will hit, we have no way of knowing whether the fungicide would respond with increased yields, or whether it would hurt yields or hurt bean quality."

Can soybeans that are planted extremely late benefit from foliar fungicide?

"So while we understand why growers might be cautious, we've never had a chance to see how soybeans planted as late as the first week of July might react to fungicide application," Mueller says. "Each year creates a learning opportunity, so next time we have a wet spring followed by a dry summer we will have data to show how fungicides perform in those conditions."

For those who'd like to help increase the available data on soybean fungicide application, Mueller says the On-Farm Network has some fungicide product available for trials and will deliver it. "We'd really like to know if extremely late planted soybeans can benefit from a fungicide," he says.

For more about On-Farm Network fungicide studies, see the 2013 On-Farm Network Conference presentation and the March 2010 On-Farm Update. For information about other ISA On-Farm Network studies, email Tristan Mueller at [email protected]

Cover Crop Replicated Strip Trials--opportunities with the On-Farm Network

The On-Farm Network is looking for growers all around the state who are interested in conducting replicated strip trials with cover crops this fall. Preferably, these trials will be seeded into standing crops. "We have seed available and can also provide assistance with seeding," says Mick Lane, communications director for the On Farm Network.

"As part of our work with the USDA Natural Resources Conservation Service in Iowa, we're also looking for growers located in the Upper Cedar River Watershed in northeast Iowa who would be willing to put out at least one of these trials. We need 10 trials in this areas," he says.

The On Farm Network staff is teaming up with ISA Environmental Programs and Services in the Upper Cedar River project. Environmental Programs and Services is looking for growers in other specific watersheds, as well.

If you'd like to participate, or have questions regarding this work, email Tristan Mueller, or call him at 515-334-1075. He'll either have answers for you or get you in touch with someone who can help.

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