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Be On The Lookout For Soybean Pests

Be On The Lookout For Soybean Pests
Aphids, white mold and soybean cyst nematodes can all impact yield.

By Jennifer Bradley

Soybean pests can cause havoc on yields if not monitored and addressed in a timely manner.

Shawn Conley, a soybean and wheat Extension specialist at University of Wisconsin-Madison, says there are three soybean pests farmers should be on the lookout for this year – soybean aphids, white mold and soybean cyst nemotode.

Soybean aphids
Aphids were found in unusually high populations early this summer, especially in the western areas of Wisconsin. In late June, Conley said Arlington was already at 150 aphids per plant. He suggests that farmers should be scouting them, watching for a 250 aphids per plant threshold and then start more aggressive management methods.

GOING BUGGY: Soybean aphids are out and farmers should be scouting ready to spray if there are more than 250 ahpids per plant.

"With this year's crop, it could be an issue," he adds. He explains that historically west central Wisconsin has been the soybean aphid's preferred location, but that farmers across the state should be watching for white mold.

White mold
Conley says that it may be a little late in the year to manage white mold, but famers should be scouting regardless. He recommends watching the highest-producing soybean fields, especially those which had seeds in the ground early, around May 15.

"Those are the fields we really need to target and get a handle of what's going on," he says. Conley adds that scouting can be a collaborative effort of looking for white mold and aphids in the same field walk-through.

Soybean cyst nematode
The Wisconsin Soybean Marketing Board offers farmers the ability to submit up to four soil samples per year for free evaluation of soybean cyst nematode infestation. (Visit for additional details.) Conley says this service is valuable because it allows farmers to receive risk index tables of corn nematode as well as this year's soybean nematode population.  In a traditional rotation, this helps farmers realize the risk of corn nematodes the following year, as well as soybeans in two years. An agronomist or crop consultant can aid in defining effective management techniques.

"It's a lot of good information for making management decisions that's free," Conley says, explaining all the testing is funded by the WSMB.


What is soybean cyst nematode?  Soybean cyst nematode enters into the root system and causes damage to the root of the soybean plant, Conley explains. It decreases the actual growth of the root, minimizing the amount of water and nutrients the plan then absorbs, and also decreasing field yields.

"It has been identified in almost every soybean-producing county in Wisconsin, but many growers simply don't sample," he adds.

The WSMB's website explains that soybean cyst nematode is the most serious soybean pest in the country, contributing up to $1 billion in yield losses each year.  While most nematodes are harmless, in overwhelming numbers, the damage can be drastic if not monitored, Conley says.

He adds that soil-applied insecticides are being used less and resulting in a build-up of the corn pathogenic nematode. Conley gives an example of last year's crop 15% to 20% of soil samples tested for corn nematodes came in at moderate to high risk. Conley says if farmers don't know they have an issue, they are missing a powerful way to maximize yield and also financial gain.

"You can be experiencing yield loss and not even realize it," he notes.

Growers can apply insecticides if they have the path to do so with a planter box, but the simplest way is to use a seed treatment. It also doesn't need to be done on every acre, but with educated decisions, growers are able to target the areas the nematodes are greater in. Conley says, soybean nematodes are everywhere, but most prevalent in the west central, northwest central, southeastern and  northeastern areas of Wisconsin.

"A grower can say 'my soybean yield has plateaued. What's going on here,' but never realize the base problem is the soybean cyst nematode," Conley explains. "Sampling in 2013 will help maintain nematodes in 2014 corn and 2015 soybean fields making for productive fields and happy farmers. As Conley says, "Cool beans!" 

Bradley writes from East Troy.

TAGS: Soybeans
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