Organic and Biological Control of Plant Diseases

Organic methods involve growing and maintaining healthy plants without using synthetic (man-made) fertilizers, pesticides, hormones, and other materials.
Organic and Biological Control of Plant Diseases - Articles


In organic disease control, natural materials (things found in nature or that exist in the environment) can be used to inhibit or prevent the activity of plant pathogens. Sources of information on what are considered to be an organic control material include the Organic Materials Review Institute website and the National Organic Program of the US Department of Agriculture

What is considered 'organic' is not well defined. For example, chemicals extracted from plants are considered to be 'organic' even though they are concentrated by man-made processes. Also, salts of copper and iron are found in nature, processed for use, and termed 'synthetic' but are allowed to be used with some restrictions (used in a manner that minimizes accumulation in the soil) and are considered to be 'organic.' Visit the Organic Materials Review Institute website for some specific materials.

Below is a partial list of organic materials and the pathogens listed on their labels as being controlled. This list may not comply with all the requirements that must be met in order to be 'certified organic.' You, the user of the information provided here, must find out if the material can be applied and be 'certified organic.'

Organic control materialTarget pathogens on one or more of the product labels
CopperAlternaria, Erwinia, Pseudomonas, Xanthomonas, Cercospora, Colletotrichum, Cladosporium, Powdery mildew, Downy mildew, Phytophthora, Pythium, Mycosphaerella, Phomopsis, Taphrina, Elsinoe, Gnomonia, Fusicladium, Nectria, Phyllosticta, Diplocarpon, Albugo, Guignardia, Botrytis, Exobasidium, Entomosporium, Exobasidium, Pestalotia, Phoma, Cristulariella
Oils derived from plant extractsPowdery mildew
Potassium bicarbonatePowdery mildew
Potassium silicatePowdery mildew, Pythium, Botrytis, Fusarium
SulfurPowdery mildew

'Biological' control of a plant disease involves the use of one living organism to inhibit the activity of a living plant pathogen. Biological control agents (BCAs) are registered for use by the Environmental Protection Agency (EPA) and have labels very similar to those for chemical pesticides. BCAs can be hazardous to the applicator and all safety equipment recommended on the label should be used. BCAs may have to be applied more than once in order to maintain adequate protection. Follow the label recommendations for the amount to use, the method of application, application intervals, and the restricted entry interval (REI). BCAs can be used on the same crop with chemical pesticides with some precautions. In general, a BCA should be applied 10 days before or 10 days after applying a chemical. Always consult the product label of the BCA to determine whether or not it can be applied in conjunction with a chemical pesticide. Below is a partial list of BCAs and the pathogens listed on at least one of the product labels as being controlled:

Biological control agent (type of organism)Trade Name (IPA reg. no.)Target pathogens on one or more of the product labels
Agrobacterium radiobacter (bacterium)Galltrol A (strain 84) (40230-1)Agrobacterium tumefacians (crown gall)
Ampelomyces quisqualis (fungus)AG10 (55638-16)Powdery Mildew
Bacillus subtilis (bacterium)Companion (GB03 strain) (71065-1)Pythium, Fusarium, Phytophthora,
Serenade (69592-4)Rhizoctonia, posdery mildew
Rhapsody (QST 713 strain) (69592-10)Colletotrichum, Erwinia, Pseudonomas,Xanthomonas, Diplocarpon, Cercospors
Cease (69592-19-68539)Venturia
Candida oleophilaAspire (55638-29)
Gliocladium catenulatum (fungus)primastopPythium, Rhizoctonia, Botrytis
Steptomyces lydicus (actinomycete, fungus-like bacterium)Actinovate (73314-1) Actino- Iron (73314-2)Pythium, Fusarium, Phytophthora, Rhizoctonia, Botrytis ,powdery mildew, downy mildew, Sclerotinia, Verticillium.
Steptomyces griseoviridisMycostop (64137-5)Botrytis, Alternaria, Phomopsis, Pythium, Fusarium, Phytophthora
Trichoderma harzianum (fungus)PlantShield (68539-4) or RootShieldPythium, Fusarium, Phytophthora, Rhizoctonia, Botrytis, powdery mildew, downy mildew, Sclerotinia
Trichoderma virens (fungus)SoilGard (70051-3)Pythium, Fusarium, Phytophthora, Rhizoctonia, Botrytis, powdery mildew, downy mildew, Sclerotinia