Can healthy soils and foliar sprays reduce the mycotoxin risk in crops?

Author: Brian Springer – Technical Manager: Alltech Crop Science

Click below to listen to the Mycotoxin Matters podcast episode with Brian Springer hosted by Nick Adams. You can also hear the full audio or listen to the episode on Apple Podcasts or Spotify. You can find an edited transcript at the bottom of the page. 

The mold and mycotoxin challenge

The infection of crops by fungal pathogens has the ability to reduce crop yield and quality, however, what is often of greater concern to livestock producers is the secondary metabolites which these fungi produce. These secondary metabolites, more commonly referred to as mycotoxins can lead to significant negative impacts on health and performance when ingested by livestock. The majority of molds and mycotoxins which impact grains and forages will develop pre – harvest, and despite the ubiquitous nature of these feed contaminants, this does not stop both the crop and livestock sectors trying to find ways to reduce the risk of molds and mycotoxins proliferating and causing unwanted problems.

Weather conditions, either too wet or too dry is often the biggest contributing factor to mold development, and unfortunately  as producers this variable is impossible to to control. However, there are some basic management strategies which can be deployed to reduce the mold and mycotoxin burden in crops and feeds, these include:

• Early planting of crops
• Reducing drought stress via irrigation
• Minimizing insect damage
• Early harvesting
• Avoiding kernel damage during harvest
• Drying corn to 13% or less moisture content
• Effective consolidation and sealing of forage clamps
• Effective storage and feed out practices

Breaking the disease cycle

When seeking to reduce the mycotoxin risk pre – harvest, the primary goal is to interrupt the growing conditions of certain molds and other pathogens that can produce the mycotoxins that we are concerned about.  While there are many different mycotoxins coming from many different mold sources, this blog focuses on the fusarium mold, one of the most predominant pre – harvest mold challenges. In addition to the basic recommendations highlighted above, there are some other factors that we need to be aware of that can make the plant more susceptible to these types of infections.

It is well documented that fusarium can easily infect stressed plants.  Stressors to look for  include herbicide injury, foliar diseases, hail damage, drought, and more importantly soils with unbalanced fertility.  Excess nitrogen in a corn crop is easily one of the greatest culprits.  Even if the total amount of nitrogen being applied is appropriate for the crop, by doing this in a single application instead of multiple applications throughout the season creates stress and nutritional imbalances in the plant.  This nutritional stress weakens the plant and makes it more susceptible to pathogens and disease.

Another means of interrupting the fusarium growth cycle is managing field residue. While realizing that no-till cropping methods have significant benefits and grain producers will continue to use this method,  we must consider the fact that this practice does increase the carryover of diseases that can cause mold and mycotoxin problems. To allow us maintain the residue that improves our soil health, nutrient cycling, and to reduce runoff in our fields, producers must look to use management practices other than tillage alone in the battle against fungal challenges.

The soil and microbial relationships

We need to look at the microbial relationships in the soil and how we can work with those to make the improvements that we need.  By increasing the number of good microbes in the soil we can outcompete and reduce the number of unfavorable microbes that are present. This will limit the potential challenges that may come with unhealthy soils.  The reason that this works is because when two competing microbes meet in the soil, or on a plant, they both exude metabolites to kill the other one.  The loser is broken down and recycled either by the plant or other microbes in the environment.  Alltech Crop Science utilizes bacterial metabolites to kickstart this process and encourage the beneficial microbes that we need as part of a solid prevention program.

Fungicide application

Another common way that producers will try to reduce potential mycotoxin problems is by spraying a fungicide.  For fungicides to be effective in reducing mycotoxins, the particular fungicide used must be totally lethal to fusarium. If they are not, they will stimulate mycotoxin production1.  What this means, is that for the 40-60% of the colonies that are not killed with a fungicide treatment, this additional stress can actually increase the amount of mycotoxins produced, even with fewer colonies.  For example, strobilurins type fungicides ( which control leaf diseases like common rust and Northern corn leaf blight, will exacerbate vomitoxin/don problems3.  The recommended dose of fludioxonil plus metalaxyl-M causes inhibition of hyphal growth of Fusarium but enhances sporulation and mycotoxin production by Fusarium2.   Studies have shown a relationship between the onset of sporulation and mycotoxin production.   Once again, using bacterial metabolites to outcompete the mold and reduce their numbers, but unlike several of the fungicides, they do not cause a spike in mycotoxin production.

A preventative approach to fungal infection

Weather and soil conditions are both large contributing factors to plant disease and the subsequent reduction in crop quality.  By giving the plant the best, limiting disease and stress, and supplying adequate nutrition, we can increase the chances of having a healthier and higher quality crop, and reduce the risk of mold and mycotoxin development.  Crops are faced with challenges that are caused by fungus, disease and environmental conditions. Alltech Crop Science recommends taking a preventative approach to decrease the chances of the plant being infected, or at least reducing the impact if crops do become exposed to these challenges. The Alltech Crop Science product range focuses on bridging the gap between the yield potential of the plant, and the yield that we receive when environment and climate have affected the crop.

Even where the most robust pre – harvest management strategies have been employed to reduce the mold and mycotoxin burden, the risks can rarely be totally eliminated. The Alltech Mycotoxin Management Program takes holistic view of mycotoxin control, and it is recommended to test incoming feed ingredients using tools like Alltech 37+® or Alltech® RAPIREAD™. Accurately identifying any potential mycotoxin threat post – harvest allows producers makes the most effective decisions when it comes to managing the challenge.