How Can a Fungus Survive Seed-Applied Fungicides?

- Dan Custis

If we use a fungus as a beneficial biological seed treatment, how can it coexist and thrive when used in combination with other seed-applied fungicides? A fungicide should kill a fungus, right?

Trichoderma is a soil-borne fungus and occurs naturally all over the world. As of 2015, at least 250 species had been identified and classified, and this list continues to grow as new species are discovered.

A main focus for all companies producing biological products is the challenge of delivering living organisms into a production agriculture environment. The seed coat, phyllosphere, furrow, tank mix, etc are all harsh environments with their own hazards, and great care must be taken to ensure biological survivability. Different companies take different approaches to making this happen with a mixture of results. When evaluating a biological product, be sure to ask: What steps have been taken to ensure product viability and efficacy – Specialized use instructions? Encapsulation? Over-formulation?

When it comes to Trichoderma, ABM’s approach is threefold, but all stem from natural properties of the fungus. First, our Trichoderma-containing products are applied to the seed as dormant spores. Spores are highly resistant survival structures used by Trichoderma and other fungi to survive harsh environmental conditions over time. We specifically formulate our products using these naturally-occurring spores with the aim of delivering longer shelf-life products that are compatible with a wide range of seed-applied chemicals.

Second, Trichoderma is a fungus that is resistant to most agricultural fungicides. This property is unique to Trichoderma and one of many reasons that ABM has chosen to develop products with it. The result is that even though we apply Trichoderma to seeds in combination with, or over the top of, chemical fungicides, these chemicals do not affect our strains.

Finally, the strains of Trichoderma ABM uses in its products grow aggressively once they are put into the soil. They establish their niche in the rhizosphere surrounding the seed and inside the plant’s roots. They rapidly grow out of other seed-applied fungicide’s immediate zones of efficacy. ABM’s seed-applied Trichoderma organisms are not intended to be free-living in the soil or to remain on the seed. Rather, they colonize along the root hairs and inside a plant’s internal compartments. This leaves little opportunity for the Trichoderma to be damaged by seed-applied fungicides.

That’s the beauty of Trichoderma: it’s broadly resistant to chemistry-based fungicides and quickly colonizes a plant’s root system. These basic properties of the genus allow ABM to provide functional biological products, giving growers maximum flexibility in their input choices.

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