Editor’s note: The following was written by James Specht, University of Nebraska emeritus professor of agronomy; Loren Giesler, Extension plant pathologist; Robert Wright, Extension entomologist; and Randy Pryor, Extension educator, for the university’s Crop Watch website Nov. 8.
Farmer question: “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?”
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.
Before deciding about seed treatments, soybean producers should answer four questions.
- Field history: Is there a history of seedling/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 history: We recommend a preventative fungicide treatment 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 level Phytophthora control. 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 SDS, 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 vs. past yield losses to SDS in the field. It is important to 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.
With a late planting date, fungicide seed treatment is not necessarily cost-effective.
More than 38 replicated, UNL on-farm research trials have been conducted with soybean seed treatments (fungicides and/or insecticides) since 2000.
To view the results of these trials, search at http://resultsfinder.unl.edu/.