Strategies for lessening the impact of Asian soybean rust

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Strategies for lessening the impact of Asian soybean rust

Asian Soybean Rust
Soybean Rust Profiled Soybean Rust Impact Control

It is hard or even nearly impossible to prevent the arrival of Asian soybean rust (soybean rust) as it is distributed by the wind onto your fields. At this time there are no known soybean rust resistant soybean plant varieties, although ScienceDaily reported in April 2009 that scientists from the Agricultural Research Service (ARS), Iowa State University (ISU) and Brazil have together identified a cluster of soybean genes that provide resistance to the fungus Phakopsora pachyrhizi, which is the more aggressive of two fungi, the other being P. meibomiae, which cause soybean rust. While using resistant varieties is not on the strategy board, for now at least, there are some other strategies that may reduce your soybean rust losses including a recent report on tools for rust-resistance.

Variety Selection

It has been reported that early maturing varieties of soybean plant for your specific geographic region could escape some of the worst affects of yield reduction due to soybean rust. However, on the downside, it is likely that a good number of these early maturing soybean plants have lower yield potential when compared to full-season varieties.

Planting

With disease suppression in mind rather than eradication, early planting has been advocated, although this could lead to other problems, such as white mold. Another strategy that has been put forward with unknown effect is planting a wider row width and thus having a lower plant population. The theory behind this is that it could reduce the amount of time that the soybean leaves remain wet and therefore open for soybean rust spore infection.

General Husbandry

The advice here is to keep doing what you are probably doing already:

Aim for a high yield.
Plant at your normal early planting date, if you can.
Make sure you continue to control other pests and diseases.
Keep your plants as healthy and as stress free as you can (early planting can reduce plant stress).
Keep your regular tillage and crop rotation practices.
Be prepared to apply fungicides.

Fungicides

Until there are soybean rust disease resistant plant varieties available the only really effective weapon against the soybean rust disease is the application of fungicides. Products such as, Bumper, Domark, Folicur, Headline, Laredo, PropiMax, Quadris, Stratego and Tilt are all potential weapons in your armoury for lessening the effects of soybean rust.

The effectiveness of the application of a fungicide, whether it is a protectant variety or a curative variety, is largely down to timing. Research thus far has indicated that soybean rust outbreaks vary from endemic to seasonal. The fungicide is most effective when it is applied before the soybean rust spores arrive on the leaves. However, spray too early and the fungicide protection may dissipate prior to spore infection. Spray too late and again the fungicide protectant will not be effective and the curative fungicide will be limited in its activity. Early detection of soybean rust is therefore vital if you intend to apply any fungicide. One note of caution: the University of Wisconsin-Madison (UW) Soybean Plant Health unit reports that research from Brazil has shown that once 20 percent to 30 percent of the soybean leaf canopy has been infected by soybean rust then fungicides are no longer viably effective to prevent further infections. Be vigilant, and spray at the right time because the cost to growers of an ill-timed fungicide appliction is likely to be significant.

Useful Links

EPA (www.epa.gov)

FDA (www.fda.gov)

USDA (www.ams.usda.gov)

TPMA (www.tpma.org)

Maryland (www.mda.state.md.us)

West Virginia (www.wvagriculture.org)

Kentucky (www.kyagr.com)

Virginia (www.vdacs.virginia.gov)

North Carolina (www.ncagr.gov)

South Carolina (www.state.sc.us/scda)

Alabama (www.agi.state.al.us)