Sprayer in field
THINGS TO CONSIDER: Farmers looking to order their soybean seed will want to consider planting dates and field history when deciding whether to add fungicide and insecticide treatments.

When does soybean seed treatment pay?

Before deciding on soybean seed treatments, consider field and disease history, and planting date.

A Nebraska farmer posed this question about soybean seed treatments: I want to book soybean seed this fall for 1,000 acres of soybeans. I have always ordered seed treated with fungicide and insecticide. But at $20 per unit, does soybean seed treatment pay? I have been following the University of Nebraska-Lincoln recommendation of planting soybeans early.

Farmers looking to order their soybean seed will want to consider planting dates and field history when deciding whether to add fungicide and insecticide treatments.

Many farmers are looking for ways to trim input costs due to lower commodity prices this year. Cutting costs is usually not easy and needs to be done without reducing profitability. Fall soybean seed purchases require farmers to decide about seed treatment without knowing what weather risks they'll face next spring.

The prime culprit with soybean seedling diseases is saturated soil conditions coupled with cold temperature leading to slow emergence. Reduced seedling populations may be spatially erratic, especially in poorly drained areas, and cause spot-replant in those areas.

Factors to consider
Before deciding about seed treatments, soybean producers should consider these four factors:

• Field history. Is there a history of seedling or emergence problems? If the field has a history of stand problems, treat the soybean seed with a good combination fungicide product.

• Early planting. If you are planting soybeans early, as recommended by Nebraska Extension, fungicide seed treatments are a necessity. Cool, wet soils are very conducive to poor stands. No-till fields will have cool soils longer into the season than tilled fields and commonly will have more seedling disease problems.

• Phytophthora disease. A preventive fungicide treatment is recommended on fields with a history of phytophthora. These fields will need the appropriate fungicide package with the proper seed treatment rate for moderate to high phytophthora control. Examples of active ingredients are metalaxyl, mefenoxam or ethaboxam fungicides with excellent phytophthora ratings. Even with resistant soybean varieties, we recommend a fungicide seed treatment as fields with phytophthora also favor pythium.

• Sudden death syndrome. In fields with a history of sudden death syndrome, soybean producers should consider using the soybean fungicide treatment ILeVO. This product has shown promise for addressing SDS in recent university and industry trials. You'll want to analyze the price of the treatment versus past yield losses to SDS in the field. Consider the percentage of the field that has been impacted historically in this decision. Some fields might benefit from using treated seed in only a portion of the field.

More than 38 replicated, UNL on-farm research trials have been conducted with soybean seed treatments since 2000. View the results of these trials at the Nebraska On-farm Research Network.

Insecticide soybean treatments
There is another caveat when it comes to early-planted soybeans. In many years, overwintering bean leaf beetles (BLB) are attracted to these early-planted or "magnet" fields. Typically, BLB feeding on unifoliates and first trifoliates is inconsequential to soybean yield, so insecticide treatment to reduce feeding is not warranted. However, if the overwintering BLBs carry the bean pod mottle virus, they can vector the BPM virus to young soybean seedlings before they lay their eggs in the soil next to the seedlings.

The infected seedlings go on to be BPMV-infected plants, serving as a potential disease reservoir for later emerging BLBs. The disease can transmit from these early-infected seedlings to many more plants. To stop the early-BLB vectoring of BPMV to your early-planted and likely highest-yielding fields, we recommend insecticide-treated seed be used for at least late-April planted varieties. Insecticide treatments for later-planted fields are not recommended, unless you have experienced bean leaf beetle BPMV infection in the past.

This report comes from UNL CropWatch.

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