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How to prevent Pythium-based yield losses

January 18, 2023 3:37 p.m.

By Valent

Todd Mayhew, Director of Seed Protection at Valent U.S.A., encourages growers to take a proactive management approach to pests, like Pythium, that rob yields from the roots up.

What is Pythium?

Pythium species comprise a group of more than 200 plant pathogens that can have a variety of hosts including crops, animals, and even humans. Pythium species are also called water molds, and are highly persistent in crop fields. It’s extremely important to manage Pythium populations, as these pathogens will likely withstand both soil moisture and temperature changes, increasing without proper management.

What does Pythium affect?

Pythium has a variety of hosts and is one of the most common crop diseases for growers. Cereal crops, such as winter wheat, are known to be susceptible to Pythium damage, with the pathogen attacking seedlings before, during and after emergence. Damage caused by Pythium varies, with root rot frequently being among the most detrimental. The first weeks after seedling emergence pose the highest risk for Pythium root rot to develop, according to South Dakota State University Extension.

Diagnosing Pythium Diseases

Pythium can be challenging to diagnose, especially given its ability to remain viable through changes in soil temperature and moisture. If the weather is not conducive to disease in one year, the pathogen stands ready to strike the following year. According to University of Minnesota ExtensionPythium thrives at 50-68°F and in saturated soils, and can develop rapidly under those conditions.

“Don’t be complacent against these pests,” Mayhew says. “In many cases, once you’re seeing damage in the field, you’re beyond the window to prevent losses.”

One of the first observable symptoms of Pythium damage is soil appearing to stick to the end of the seed embryo. According to Oregon State University Extension, the appearance is caused by soil adhering to Pythium’s sticky “threads” of hyphae. Depending on the severity of the infection and season, other symptoms include, but are not limited to, reduction in plant population, wilting, discolored roots, stunting, and even plan death and decay. The Crop Protection Network, notes that symptoms are generally more noticeable in low lying areas, with infected roots appearing shorter, having fewer root hairs, and with the outer layer of the root (cortex) falling off easily. Symptoms may appear from seedling stage to ripening.

Preventing and Managing Pythium

Once Pythium takes hold in a field, it’s extremely difficult, if not impossible, to manage. Seed treatments are often a producer’s strongest tool to control Pythium in-season, and a seed treatment containing metalaxyl can help prevent early infection. Ensuring the availability of nutrients like phosphorous and nitrogen can further help reduce infection in crop roots.

Seed treatments protect growers’ investments in seed and support a strong start for crops. “Take an integrated approach at planting,” Mayhew says. “A treatment like INTEGO® Suite Cereals OF protects without requiring additional passes across the field during the growing season.”

Although metalaxyl is effective in preventing infection, in recent years researchers have detected an increase is metalaxyl and mefenoxam-resistant Pythium.  Producers seeking solutions for Pythium-related root rot and other symptoms have a variety of options. INTEGO® SUITE Cereals OF,  available through local retailers, provides a superior option for controlling Pythium on cereal crops. It offers easy use with an innovative formulation that supports even coverage and performs in a variety of temperatures. INTEGO® SUITE Cereals OF not only contains metalaxyl, but it also has ethaboxam (FRAC group 22) that protects plants from the Pythium species that are metalaxyl resistant. Ethaboxam has a different mode of action and is both less soluble and less mobile than metalaxyl or mefenoxam and is a great tool for producers to for resistance management.

Take the Next Step on Pythium

For more information about INTEGO® SUITE Cereals OF and other solutions from Valent U.S.A., contact your local representative or visit