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Corn+Soybean Digest

Treated Soybeans Bring Benefit with Early Planting, Wet Conditions

Some would argue that 2009 stirred up the perfect storm for preventing early planted soybeans from making a stand. Replanting was needed over much of the bean belt. But if you planted treated seed, you were likely sheltered against many massive seedling setbacks.

“In the wettest areas, we probably saw only a 10-15% stand establishment on untreated soybean seed. But stand establishment was 50-75% for treated seed,” says Jared Bergmann, certified crop specialist for Southern FS in Murphysboro, IL. “If you're planting soybeans early, you'd probably be foolish not to use treated seed.”

Palle Pedersen, technical manager with Syngenta Seed Care and former Iowa State University (ISU) soybean specialist, says growers planting early to push for high-yielding beans will get their money back for treatment costs particularly in areas with been leaf beetles, but also “if they would prevent having to replant even once in four or five years because of seedling diseases.”

However, if growers are forced to plant in late May or into June, use of treated seed should still be considered. Despite higher soil temperature and more rapid emergence, late planting may often be related to replanting and/or wet conditions early. Planting in warmer soils, and often wet soils, could be the perfect “setup” for Phytophthora root rot that can cause significant stand loss, says Pedersen.

Arguments for and against treating soybean seed with fungicides, insecticides and/or inoculants have been heard a lot the past decade. As the cost of seed has increased, so has the pro-treated-seed talk.

IT USUALLY BOILS down to whether you have fields that are susceptible to diseases like Pythium, Phytophthora, Fusarium, Rhizoctonia or others that can thwart germination and ultimately prevent a good stand establishment. Fungicide treatments for such diseases will likely include metalaxyl, mefenoxam, azoxystrobin, captan, carboxin, fludioxonil, PCNB, thiram or thiabendazaole.

Protection against bean leaf beetle, seed corn maggot, wireworms and other insects can also be provided through insecticide seed treatment.

“We face pressure from those insects, as well as Pythium, Phytophthora and Fusarium,” says Bergmann. “If you're planting early to push for proven higher yields, you should look hard at having treated seed in your budget.”

He points out that with the wet weather in 2008 and early 2009, “a lot of growers were dissatisfied with the stands they saw. That will probably convince more to go with a seed treatment program.”

The lack of stand establishment during germination is a sign of seedling disease in your field, says X.B. Yang, ISU plant pathologist. “Using seed treatment is a must in replanting,” he says. “However, insects such as seed corn maggots sometimes cause seed rot. Make sure the lack of soybean stand is from disease, not insects, when you replant. Or to help you, use a product that includes both an insecticide and a fungicide.”

Pedersen reminds growers that “seed treatments with insecticide do an outstanding job on the overwintering generation of bean leaf beetles and will suppress soybean aphid population for at least 60 days after planting, and in many cases delay the time before they reach the threshold, if they do, by one to three weeks.”

The cost of a typical fungicide and insecticide seed treatment a is $8-10/acre. When seed costs were about $15/acre, treatments weren't as popular. But higher input costs have changed many growers' thinking.

“You don't want to have to replant if seed costs $50-60/acre,” says Pedersen. “It's easy to get your money back by not having to replant.”

STILL, PEDERSEN FIGURES that only 30-40% of soybean seed is treated in Iowa, but the acres have increased every year since farmers now are aware of the importance of early planting to maximize yield. Bergmann says the rate is only about 10% in his southern Illinois region.

“They see it as an additional cost,” says Bergmann. “They see it as a liability, especially if they have some left over and have to sit on it.

“But there is a payback there for using treated seed,” he says. “You may not see it in overall yield, but it can help you get a stand establishment earlier. There are a lot of benefits over just getting a better yield.”

He says about half the seed treatments include a fungicide and inoculant seed coating. The other half would feature a fungicide, insecticide and inoculant coating.

Pedersen compares a soybean seed treatment to insurance. “When you have it, you may not need it. But when you need it, you may not have it,” he says.

He adds that lower plant populations may not require being treated more than high populations. “My data show that the value of a seed treatment is the same whether the plant population is 125,000 or 250,000,” says Pedersen. “But the chance of having to replant is higher if the plant population is lower.

“Seed treatments should also be looked at as a risk-management tool. There will be areas where you likely don't have as much insect pressure as other areas, areas where you don't have a lot of seedling diseases. But with our variable weather in the spring, nobody can really predict before planting what kind of year that it will be.”

He points out that with most corn seed now either Bt or treated, soybeans can see greater insect pressure.

“When you change something in your system, you are opening up the door to something else,” says Pedersen. “Previously, we used a lot of insecticide on corn fields, which provided a lot of residual for soybeans. Now, with triple-stack corn (with Bt protection), we're beginning to see more insects coming into bean fields.”

Pedersen encourages growers to consider these general rules to follow in planting soybeans: First, don't mud-in your beans — plant early and follow local recommendations — aim for a good stand and avoid having to replant because it lowers yield potential (and you also have to buy more seed). Second, know the condition of the seed, particularly the germination of the seed lot.

Bergmann says seed treated by his co-op is either through onsite systems or via a mobile treatment trailer. “We can treat seed at the plant or at the farm,” he adds. “We're hoping to see a few more acres treated in the coming season. I think growers will see benefits from it, especially if we have another wet, cool spring.”

There should be no argument against that.

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