Optimizing biopesticides in vegetable crops

Consumer interest in more environmentally responsible processes continues to grow. Biopesticides – pest control agents derived from natural sources such as bacteria, fungi, animals and minerals – are an alternative to conventional synthetic products. But in the battle to control increasingly resistant pests, is it possible to reconcile organic with yield?

Powdery mildew on peppers is caused by a fungus that causes yellow spots on the upper surface of leaves.

According to Dr. Margaret Tuttle McGrath, professor of plant pathology and biology at Cornell University in New York, part of the solution lies in a better understanding of the pathologies and the products used to control them. “Biopesticides can replace copper, Mancozeb and Chlorothalonil, a chemical pesticide whose use is controlled by the Pest Control Products Act in Canada. The integration of biopesticides in an integrated pest management program allows us to reduce the use of synthetic products and chemical residues on crops,” explained the plant pathologist specializing in the management of vegetable crop diseases during a conference presented as part of Horticultural Fridays last December.

Benefits to be improved

Most biopesticides have a low toxicity for pollinators and a short residual life span. They degrade rapidly, which limits their environmental impact. Most of them have short safety periods, allowing for rapid resumption of work in the field. They can also be used safely towards the end of the production cycle. Another significant advantage is that their complex modes of action help prevent the development of resistance.

The importance of a targeted intervention program

Diseases can be difficult to control, especially when conditions are favorable. Here, a “concentrated” formula is not necessarily more effective. Pesticide evaluations to date tend to show that alternate or combined modes of action (e.g., organic copper fungicide and conventional pesticide) are more effective. This observation does not exclude a strictly organic approach, provided that closer treatment intervals are adhered to. For François-Gycelain Rocque, farmer and co-owner of La Marmite du Terroir, optimization begins with “reasoned” agriculture. This practice, which aims to achieve economic targets while respecting nature, advocates a limited use of field interventions, with the right product, at the right time, using processes that are less harmful to the ecosystem. “In agriculture, soil quality is the most important element. Reducing the application of products that cause plant stress is more respectful of the environment and human health. And the vegetables you grow taste better,” says Rocque.

Realistic expectations

While most biopesticides are approved for organic growing, bacterial and root disease treatment, and are largely non-toxic, no product is completely risk-free. Some biopesticides can be harmful to beneficial organisms; others require protective equipment to be worn during application. It is therefore imperative to understand the action of the product to get the most out of it. Because it works by contact, be sure to reach the underside of the leaves for maximum effect.

Success is measured by the suppression index, but there is no absolute control. Biopesticides do not have curative properties, so they are more functional in a preventive mode.

Regardless of the protocol used, understanding crop cycles and inducing plant resistance to pathogenic factors (environment, soil, climate, etc.) remains the basis for a targeted, effective and greener program.

Source : Laterre.ca