How to Protect Corn Yields Following Cereal Rye

Pathogens at Play

One of the reasons corn may suffer after cereal rye is if the rye is serving as a “green bridge,” where pathogens that were infecting the rye move onto the growing corn as the rye dies.

  • Fusarium graminearum — which causes several diseases, including stalk rot and ear rot of corn, head scab of wheat, etc.
  • Pythium sylvaticum — which causes corn and soybean seedling disease

What About Other Small Grains?

Given the negative effects seen with cereal rye, you may be wondering if similar results would occur with other small grains.

Allelopathy’s Involvement

Allelopathy — when a plant releases chemicals to inhibit the growth or germination of other plants — may also be playing a role, Robertson says.

Environment Likely a Key Factor

Even though Robertson’s research has shown corn yield reductions can occur, especially when following cereal rye, she knows that’s not always the result.

Plant in Ideal Conditions, Time Your Termination

Because the environment plays such a big role in whether disease occurs following cereal rye and other cover crops, one of the best steps growers can take in preventing a yield drag is to plant in warm, dry conditions.

Consider Seed Treatments, Reducing Rye Biomass

Growers can also try seed treatments to help protect the corn a little more. Robertson says that currently, on every single corn seed that is planted, there will be either metalaxyl or mefenoxam fungicides, which are both active against most Pythium species. Ethaboxam is another fungicide that is proven to provide protection against Pythium species. Syngenta will also be releasing another seed treatment with the active ingredient picarbutrazox, which is expected to be available in 2020.

Worth the Risk

Despite the risk of reduced yields following a rye cover crop due to seedling disease, allelopathy or another factor, Robertson doesn’t want farmers to use that as an excuse to avoid cover cropping, because it doesn’t occur consistently and there’s a good chance a grower won’t experience these problems.



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