The What, When, and Why of Using Microbials on Your Farm

The how of using microbials graphic

Microbials play a variety of roles in crop production.

Why should microbial controls be a part of an Integrated Pest Management (IPM) program? The first, and main one, is that research shows that they work. Many microbial products in the market today are backed by trial data that shows when used correctly, microbials can be a very effective way to improve plant health, suppress pest pressure, and improve yields.

“Microbials are very powerful tools,” says Dr. Surendra Dara, Strawberry and Vegetable Crops Advisor at University of California Cooperative Extension. “They have a number of benefits for the grower. Microbial control agents are either very specific (as with some viruses or Bt) or can attack a broad range of pests (as with fungi). They can have multiple modes of action, which prevents development of pest resistance. They are very safe for workers and consumers, and are a sustainable control option.”


At the Biocontrols USA West 2018 Conference in San Diego, CA, Dara presented “Microbials and IPM: What, When, Why, Where, and How?” It was a succinct summary of the benefits of microbials and how growers can fit them into their IPM programs.

There are a number of types of microbial products: viruses, bacteria, fungi, nematodes, and microsporidia. Viruses and microsporidia need to be eaten by the pest. Bacteria can be eaten or will infect the insect by penetrating the skin and multiplying. Beneficial nematodes are mobile and will seek out the host and cause infection and death.

“Research in beneficial microbes as pest control continues as we make progress on learning about all available systems,” Dara says.

Dara says entomopathogenic fungi can actually provide a double benefit in the field. The word entomopathogenic refers to “insect” and “disease,” and the fungi causes disease in arthropod pests. In addition, these fungi work in the soil and help plants with nutrient and water absorption, improving plant growth, and ultimately, yield.

“Understanding the plant-entomopathogen-arthropod interactions and exploring their potential for overall plant health contributes to sustainable pest management,” Dara says.

Dara outlined several opportunities for using microbial control agents, or MCAs:

  • Controlling certain endemic and invasive pests
  • When there is a risk of pesticide resistance, or the current pest management program is not effective with existing options
  • Controlling certain pests where chemical pesticides cannot be used
  • Situations where the environment is favorable for the use of MCAs

Because of their safety to workers and consumers, MCAs can be used throughout crop production. Seed can be treated before planting or the transplants can be inoculated after planting. The most important thing to remember when using any kind of microbial application is that it is living material, not just a chemical, Dara says. Because of that, proper storage and application is essential. If a container is left all day in a hot car or in a field in the sun, the microbes that are the active ingredient could die. Storage and application directions are on the label and must be followed.

Along with the proper storage and application, Dara emphasized some other factors important to using microbials effectively.

  • Understand different modes of action and suitability for the pest and crop situations.
  • Consider applying in the evening to provide several hours of cooler, moist conditions for the microbes to establish.
  • Know what type of tank mixes are compatible.
  • Use before pests are out of control. Don’t use as a last resort. Microbial populations need time to buildup to be effective; they are not a kill-on-contact pesticide. Pest pressure should be low or moderate.
  • Microbials can be combined with a low-label rate of a chemical pesticide to reduce the amount of chemical needed. They can also be combined with a botanical pesticide for improved efficacy.
  • Use microbials and other biological controls in rotation with chemical pesticides to reduce the risk of pesticide resistance.
  • In certain cases, research shows multiple pathogens can be combined to improve efficacy and control multiple pests.