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Applying Fungicidal Seed Treatments to Small Grain Seed
Wondering if you should treat small grains seed with fungicide or insecticidal seed treatments before planting?
Fungicides applied on seed can help protect stand establishment if there are fungal diseases present in the soil, says Madeleine Smith, University of Minnesota Extension small grains pathologist. That’s also the case for seed saved from the previous season if infected with Fusarium head blight or smuts.
Infection by fungal pathogens at or just after germination can cause seedling loss, she says. If seedlings do not die, they can have poor vigor, due to the inability to efficiently take up water and nutrients.
Then There’s Pythium
Pythium can be a problem in damp fields enduring cold weather that are at or above field capacity for moisture. Pythium can kill seedlings if infection occurs early in germination, leading to patchy stands. Infection of roots leads to browning of roots and root damage, which can ultimately lead to poor seedling vigor.
Temperatures for optimal development of Pythium range between 50°F. and 68°F. Seed treatments that contain mefanoxam (metalaxyl) can guard against early Pythium infection during germination, Smith says.
Roots however, may still become infected. Ensuring adequate availability of nutrients such as phosphorous and nitrogen at seeding can help mitigate the potential for reduced uptake by infected roots, Smith days.
Root and Crown Rots
Aside from Pythium, two of the biggest issues as far as seedling diseases are concerned in Minnesota are Fusarium root and crown rot and common root rot, says Smith. Over the last few years in Minnesota, Fusarium root and crown rot has become the most widespread of these two diseases.
Seed treatments containing tebuconazole should be effective against Fusarium root and crown rot. Other combinatory seed treatments that contain prothioconazole, tebuconazole, and metalaxyl can help suppress common root rot as well as combating Fusarium root and crown rot, says Smith.
Sedaxane, belonging to the SDHI class of fungicides, also has some efficacy against common root rot and is also effective against Fusarium root and crown rot. For an overview, check out this handout on root disease.
Insecticidal Seed Treatments
Some seed treatments also contain insecticides. These can be beneficial, especially if the crop is being planted on ground that has just come out of the Conservation Reserve Program, says Smith.
Pythium control is a consideration for cold and damp conditions at the start of the season. If the field has a history of root disease, treating the seed will help prevent stand establish problems.
It is important to bear in mind that no seed treatment lasts season long, and so infections can occur later in the season causing some damage and the potential for tillers dying back, particularly under conditions of plant stress such as dry conditions. This is often noticed as white heads, which are not due to wheat stem maggot or Fusarium head blight, says Smith.