Chapter 12

Plant Disease Management for Organic Crops

Biopesticides for Controlling Crop Diseases

Many biologically-based products are currently available, and these products are often referred to as “biorationals” or “biopesticides.” Biorational is an undefined term used in broad reference to any biologically-based product used in agriculture that includes fertilizers, pesticides, herbicides, plant growth regulators, and various other products. A biopesticide as defined by the U.S. Environmental Protection Agency (EPA) is a pesticide derived from natural materials. Biopesticides that are used by organic growers are classified as either microbial or biochemical, based on the active ingredient. Microbial pesticides include live organisms (e.g., beneficial bacteria, fungi, nematodes, and viruses) and/or their fermentation products as the active ingredient. Biochemical pesticides contain naturally occurring substances that control pests. Substances that control pathogens include potassium bicarbonate, hydrogen dioxide, phosphorous acids, plant extracts, and botanical oils. Biopesticides are key components of integrated pest management (IPM) programs, and are receiving much practical attention as a means to reduce the load of synthetic chemical products being used to control pathogens.

Classification of Biopesticides

Biopesticides that can be used by organic growers can be classified as either microbial or biochemical, based on the active ingredient. Microbial pesticides include live organisms (e.g., beneficial bacteria, fungi, nematodes, and viruses) and/or their fermentation products as the active ingredient. Biochemical pesticides include plant extracts, pheromones, plant hormones, natural plant-derived regulators, clay, potassium bicarbonate, and enzymes as the active ingredient.

Approved Biopesticides

Most biopesticides are approved for organic production and most products approved for organic production are biopesticides, thus they are a logical fit for managing pathogens in organic crops. However some formulations are not approved, which can be due to inert material(s). For example, the potassium bicarbonate products Kaligreen and MilStop are approved whereas Armicarb is not. Some biopesticidal substances are not allowed under National Organic Program (NOP), for example phosphorous acids and genetically engineered PIPs. It is important to verify that a biopesticide, like any other product is approved for organic production and registered in your state prior to any application. A list of commercially available microbial biopesticides (Table 13.1) and biochemical biopesticides (Table 13.2) are provided in the following tables.

Application of Biopesticides

The successful application of biopesticides hinges upon the grower having an in-depth understanding of the biology of the target plant pathogen(s). Biological control agents (BCAs) are registered for use by the Environmental Protection Agency (EPA) and have labels very similar to those for chemical pesticides.

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