Bean Wise: Protecting Soybean Seed from the Biggest Threats
Using a quality seed treatment is often likened to choosing the right insurance plan. In order to adequately protect yourself and your property, you have to be insured against all possibilities. Out of all the potential threats to soybean seed, the four diseases consistently impacting crop stands across the country are Phytophthora, Pythium, Rhizoctonia and Fusarium. Understanding how these diseases operate can help you find a seed treatment to cover your risk.
The two deadliest diseases, Pythium and Phytophthora, have the potential to completely wipe out a soybean crop under the right conditions. Symptoms of the two are so similar (brown and/or rotting tissue on the hypocotyl or roots) it is often hard to tell them apart, but the weather conditions can give you a clue. Both diseases affect stand in wet conditions (poorly drained soils, no-till, low-lying areas). In the northern United States, Pythium more typically thrives in early spring with cooler soil conditions (50-60°F), and is most damaging to seedlings. There are exceptions to those temperature depending on geography. Phytophthora on the other hand is more common with slightly warmer soils (>60°F) and can cause stand loss throughout the season.
Because of their severity, new seed treatments are being developed to help soybean farmers deal with Pythium and Phytophthora. Picarbutrazox is the newest active ingredient on the market. It uses a novel mode of action to control both of these seedling diseases, with particularly outstanding control of Pythium. It improves IPM and adds another layer of protection to already highly effective systemic fungicides like Mefenoxam.
Other diseases are less likely to cause stand loss, but more commonly reduce yield by stunting the growth of plants due to root system damage. When conditions are cooler after emergence, you may find plants infected with Fusarium. The roots of these plants may look similar to those with other “damping off” diseases, with brown dead tissue on the roots, but they often won’t completely die. In warmer springs or with later planting, Rhizoctonia infections become more likely. Visually, they may look stunted, similar to other diseased plants, but soybeans infected with Rhizoctonia will have reddish, sunken lesions on the stem at or near the soil line. The following are active ingredients known for their control of these diseaeses:
- Sedaxane is a newer fungicide active ingredient ideal for Rhizoctonia. Its soil mobility provides long-lasting protection of the entire root system, allowing for more robust growth.
- Azoxystrobin is a well-known systemic fungicide that adds a broad spectrum of disease protection when used in combination with other seed treatments.
- For contact activity, fludioxanil provides excellent control of Fusarium and other seed-borne diseases in soybeans.
It’s impossible to know exactly what each new season will bring, which is why choosing a seed treatment with multiple active ingredients and modes of action is the greatest form of protection. Of course, disease isn’t the only thing threatening your crop. Many of Helena’s soybean seed treatments combine fungicides with an insecticide to also target insect pests. For example, Seed Shield® Select contains five fungicide active ingredients: mefenoxam, picarbutrazox, fludioxanil, sedaxane and azoxystrobin. It also contains thiamethoxam, providing broad spectrum insect control and a patented vigor effect to optimize root and shoot development. Along with Asset® Formulation Technology, Seed Shield Select provides these components in a suspension concentrate that is expertly formulated, and easy to use with consistent ai loading and performance. Contact your local Helena representative for more information on Seed Shield Select and to learn more about soybean seed treatments and disease management this season.