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DISEASE CONTROL - CHEMICAL CONTROL

Another method of controlling plant diseases is by use of chemical pesticides such as fungicides (for control of fungi) and bactericides (for control of bacteria) and nematicides (for control of nematodes). Viruses and phytoplasmas cannot currently be controlled using chemical pesticides.

Fungicides and bactericides fall into two major groups.

PROTECTANT fungicides are those that are applied to the surface of a plant and must coat the surface to be effective. Protectant fungicides are NOT absorbed by the plant. They form a chemical barrier between the pathogen and the plant. Good coverage is critical for protectant fungicides to be effective.

SYSTEMIC fungicides are absorbed by the plant and redistributed internally. Thus even coverage is not as critical as with protectant fungicides. Systemic fungicides tend to remain effective for a longer period than protectant fungicides, because they are less likely to wear or wash off the plant, and have less exposure to environmental factors that may lead to degradation.

FUMIGANTS are another type of compound used for control of pathogens, particularly pathogens found in soil. Fumigants are general biocides. They are toxic to all kinds of biological organisms including pathogens, non-pathogens, insects, weeds, and even desirable plants and animals. I do not recommend use of fumigants in urban settings.