Soybean cyst nematodes survive very harsh winter

Soybean cyst nematodes survive very harsh winter

THE record-low temperatures experienced over the past few months may reduce some pest populations this spring, but university and industry experts predict that soybean cyst nematodes (SCNs) will still threaten yields.

While many may believe that the extremely cold temperatures this winter killed SCNs, this is not actually the case. In fact, almost 100% of SCNs survive over the winters in the Midwest — no matter how cold.

"Many growers hope the cold weather we've been experiencing will help decrease pest populations, but it doesn't affect SCN," said Dale Ireland, seed treatment technical product lead at Syngenta.

According to Iowa State University Extension, unusually large numbers of SCNs may infest fields where soybeans were grown in 2012 — a year when SCN reproduction was particularly high. The number of SCN eggs in the soil at the time of planting contributes significantly to the degree of damage and yield loss due to SCNs. With an overwintering survival rate of nearly 100%, the potential for damage in 2014 is great.

It was the most devastating pest to soybeans in the U.S., costing producers more than $1 billion last year.

Extremely high SCN reproduction was observed in Iowa in 2012 on both susceptible soybean varieties and SCN-resistant soybeans with the PI 88788 source of resistance; it was believed to be somehow related to the extremely dry soil conditions that occurred that year.

The University of Nebraska-Lincoln explained that SCN-caused losses can be reduced once a farmer knows SCNs are present in the field, but SCNs can still reduce yields by 20-30%, even when plants appear to be green, healthy and have no visible symptoms.

Often, the first indication of an SCN problem is soybean yields that hit a plateau, or even start to drop off, while corn yields continue to increase in that field. Soil testing is the best way to determine if SCNs are present.

To help manage and reduce SCN populations in infested fields, researchers at Iowa State University Extension suggest rotating crops, selecting SCN-resistant varieties and using appropriate seed treatments.

"Choosing a variety with high yield potential and good nematode tolerance, along with a nematicide seed treatment, is vital to managing SCN," Ireland said.

Volume:86 Issue:16

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