biological

It’s difficult to introduce any living organism into the environment with 100 percent certainty in the outcome, but we are getting closer and closer with biologicals. A large part of the plant environment is the microbial community, or phytobiome, that interacts with the plant throughout the season. Ignoring direct effects on the crop plants for a moment, three primary schools of thought regarding the activity of biologicals exist today: antibiosis, niche replacement and phytobiome alteration, of which the latter holds one of the most promising outlooks for agriculture today.

Molly Cadle-Davidson

Antibiosis is the use of a biological that acts like an antibiotic. The biological produces a chemical that is encountered or consumed by the target pest/pathogen with a limiting or killing effect on that organism. Streptomycin and Bacillus thuringiensis (Bt) are good examples of biologicals having an antibiosis effect.

The second school of thought is niche replacement, in which the organism outcompetes other organisms in the environment. This is true with many biologicals; they grow aggressively or consume nutrients such that other organisms around them either can’t survive or don’t reach a disease-causing threshold. Many of the biologicals applied by foliar spraying act this way.

In more recent findings, we see alterations in the phytobiome. Focusing on the plant root environment, the phytobiome is all the organisms in the soil, rhizosphere (about 3-5 millimeters around the root system), and inside the root. Unlike niche replacement, which relies on an organism outcompeting others, phytobiome alteration reconfigures the makeup of the crop-associated microbial community, recruiting beneficial organisms that are already in the soil to the plant and suppressing the bad actors.

For example, if we treat the soil or seed with Trichoderma, the Trichoderma recruits other organisms from the soil to help the root and plant grow. A good example of this is improvements seen in nodulation when Trichoderma is present regardless of whether a rhizobia inoculant has also been added. This is the result of Trichoderma recruiting an applied inoculant to more efficiently nodulate or, in the case of no inoculant, recruitment of wild rhizobia to the plant.

We are looking into the actual functional changes to the plant’s microbial environment or the phytobiome. This is new stuff and it’s where the whole industry is going.

Farmers should be really excited about this approach because current recommendations for applying chemistry and biologicals essentially ignore the environment. What’s one of the biggest variables when it comes to farming? The environment. If we know how what we do changes the environment, then we are far more in control of what happens to our crops. We’ve just touched the surface, and the future is very exciting.

This column is the second in a two-part series. Be sure to check out the first part, “Explore the Effects of Biologicals on Plants”

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