When to use seed treatment for small grains

Every year I get asked if a seed treatment is needed for small grains. Invariably my answer is:

  • Yes, if your seed lot is carrying a seed-borne disease, such as loose smut in wheat.

  • Yes, if you have a scab seed lot.
  • Perhaps, if you have a known history of wireworms in a field.
  • Possibly, if you have been in continuous small grains (>2 years) and have started to see a higher incidence of root rots like common root rot, fusarium crown rot or footrot.

In all other situations, seed treatments are very much like life insurance; it only pays when disaster strikes at the very beginning of cultivation and initial stands are reduced enough that grain yields are reduced due to lower initial stands which could not be compensated by additional tillering of adjacent plants.

The three main soil-borne fungal diseases that reduce early stands in Minnesota are Pythium damping-off, common root rot (CRR), and fusarium crown rot (FCR). While pythium likes cold, moist conditions, common root rot favors cold, dry conditions, and Fusarium crown rot thrives when conditions are hot and dry.

Understand that seed treatments do not provide season-long control. Latent CRR and FCR infections that do not outright reduce the initial stand or CRR/FCR infections that occur later in the season generally do not become evident until the middle of the grain fill period when affected plants die suddenly and become those very noticeable “whiteheads”. ‘.

Andrew Friskop, an extension plant pathologist at NDSU, analyzed a large number of seed treatment trials in North Dakota to dig a little deeper into the conditions that spell disaster so that initial stands are indeed reduced enough. to justify seed treatments. Its summary has just been published in the NDSU Crop and Pest Report and can be found here.

In the absence of the criteria listed above for the use of a seed treatment, the seed treatments in this meta-analysis of trials conducted between 2003 and 2021 showed that in approximately 70% of the trials the treatments of seeds improved the initial stands. Unfortunately, the summary plot does not show how statistically significant the difference between the initial stands should be (after all, there was experimental error in each of these trials that prevented Andrew from concluding that the increase in initial stand was due to seed treatment or luck of the draw) or whether these initial stand improvements actually improved final grain yield. Andrew also examined the influence of the amount of precipitation in the week prior to seeding and the soil temperature at seeding on the initial stand. Neither wet and cold nor hot and dry or any other combination of the amount of precipitation preceding planting and the soil temperature during planting can really explain the improvement in initial stands. The latter makes sense because the three occasional agents of initial stand reductions like different conditions.

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