Biopesticides find a place within integrated pest management

Research is ramping up on how biopesticides fit into integrated pest and disease management in vegetable production, especially for organic operations. When managing any vegetable disease, it’s essential not to depend on conventional or biopesticides alone, said Dr. Margaret McGrath.

“You want to have an integrated management program, so you’re using all your management tools,” said the professor at Cornell University School of Integrative Plant Sciences, Plant Pathology, and Plant-Microbe Biology. 

Why it matters: Biopesticides offer vegetable growers more disease management options outside of conventional fungicides. 

Biopesticides are derived from natural materials and fall into two major classes, one with a microbe as the active ingredient and the other with a naturally occurring substance as the active ingredient. 

McGrath said early research shows several microbes appear to induce systemic acquired resistance. 

“Bacterial diseases and root diseases, I think, are another good fit because there’s not a lot of decent products for bacterial diseases and root diseases and there’s a number of biopesticides labelled for these.” 

Phosphites and phosphorous acids are among the few biopesticides not cleared for organic use but have shown excellent efficacy on foliar/fruit fungal and oomycete disease. They could replace conventional contact fungicide, such as chlorothalonil, or conventional targeted fungicides. 

“That’s where you really need to understand the disease you’re going after,” McGrath said. 

“If you’re going after a disease where you need a very high level of control or a pathogen at risk for resistance developing, then an alternation program might not be the best, but better to use conventional fungicides up front.” 

However, a biopesticide could be used near the end of the season. McGrath’s research looks at biopesticide use within a conventional program for vegetable disease management. 

“It’s going to be particularly important to use a preventive spray program with biopesticides when using products such as Regalia that induce resistance,” she said. “(There’s) a number of the microbial products we think have some role in inducing resistance. So, you might want to start with a preventive application before you see the symptoms.” 

Compared to conventional pesticides, biopesticides’ short Restricted-Entry Interval (REI) and Preharvest Intervals (PHI) provide vegetable growers with a replacement option for chlorothalonil, copper and mancozeb, said McGrath. 

“They can help you reduce the amount of residues on your crop at harvest time, they tend to have a low toxicity typically for beneficial organisms, and they tend to be safer for workers,” she said. 

Biopesticides rapidly decompose and are environmentally responsible while managing conventional pesticide resistance and satisfying consumer demand for reduced pesticide use. 

“The other possibility is efficacy if you don’t have a good fungicide for a disease you’re trying to manage, or you’re not getting effective control.” 

McGrath said that while most biopesticides are safe, it’s critical to read the label, check the expiry date and follow application and storage instructions. 

“Some of these microbial products have a very short time period that they’re good,” she said. 

“There’s a lot to learn about biopesticides after they’ve been commercialized, partly because they’re getting to market a lot faster than conventional fungicides.”

When researching the efficacy of biopesticides, growers should check for field-tested research results rather than those from a controlled laboratory environment.

Growers can search for specific products or vegetable applications on the OMRI list, Canada’s Bioprotection Portal or McGrath’s database of biopesticide evaluations conducted in the United States.

McGrath said those are excellent reference points to begin building an integrated biopesticide management plan.