Disease Control
Overview
Plant pathogenic organisms infecting turf, herbaceous plants, and woody ornamental trees and shrubs
include fungi, bacteria, viruses, nematodes, and phytoplasmas. These organisms can be dispersed by
wind and water, insects, mites, and other organisms, by contaminated tools and equipment, and by
human activities such as planting, pruning, and cultivating. Although these organisms are usually
present in the environment, they often infect stressed or weakened plants. As a consequence, the key to
disease management is prevention by maintaining plant and soil health. A disease management program
should consist of a program for managing plant health that includes scouting and prevention. Client
education is another important component of disease management since not all plant diseases require or
warrant aggressive strategies for control. For example, foliar leaf spots are considered cosmetic or
aesthetic diseases as compared with blights or dieback diseases, which have significant implications for
plant health.
All relevant laws should be followed in the application of any material used as a pesticide This includes
biological and botanical products used as pesticides. State licenses are required for commercial
application of any pesticides. Check with your state government about the need for additional licenses
that might be required to care, prune, or apply pesticides in certain situations.
It is illegal to apply materials for disease management unless they are registered by the Environmental
Protection Agency and the state government and are labeled for specific plants and diseases. The label is
the law, including restrictions for use on a crop or plant species and requirements for worker protection
(such as use of protective clothing and reentry intervals). In addition, posting signs and neighbor
notification may be required, depending upon the laws in your state.
Preferred
-Building and maintaining healthy fertile soil, rich in organic matter, with balanced nutrients,
pH, and trace elements (see Soil Health). Nutrient toxicities and deficiencies can weaken
plants and make them more vulnerable to diseases as well as secondary pathogens or
opportunistic pests. Potassium has also been identified as an element that can enhance
disease resistance.
-Maintaining proper soil pH for the plant species (usually 6.4-7.0)
-Planting disease-resistant species and varieties
-Avoiding monocultures. For example: A monoculture of perennial rye grass can be heavily
infected by rust. However, if the lawn had been planted with 2-3 other grass species, the
highly susceptible perennial rye grass would be infected but the other types of grass might
be resistant or tolerant of the infection
-Carefully checking for symptoms and signs of disease on nursery stock before purchasing
trees, shrubs, or sod and by checking the root systems for evidence of disease prior to
planting.
-Using adequate spacing to promote and encourage overall plant health and good air
circulation.
-Using good sanitation practices. Pruning dead, dying, damaged, or diseased branches.
Removing infected leaves, twigs, branches, needles, and cones around the base of trees and
shrubs in the fall to remove sources of inoculum. Removing infected grass clippings from
the lawn or eliminating infected hosts and replanting with disease-resistant cultivars.
Infected plant debris should be properly composted or removed from the site.
-Developing a plant health care plan. This should include scouting to detect and identify
diseases as early as possible. Scouting should be done at least twice a month for trees and
shrubs and if possible, once a week for turf. In time, trends develop and "hot spots" of
disease activity emerge. These hot spots are often consistent and are usually associated with
microclimates that exist in most landscapes. Plotting these areas on a map works well for
future reference. It is also helpful to consult with local extension service, Experiment
station, or university personnel to keep informed about what other professionals are seeing
in the field and obtain results of disease forecasting or other prediction models.
Allowed
-Preparations of beneficial microbes with EPA labels as biocontrol agents that antagonize or
compete with specific plant pathogens.
-Potassium bicarbonate
-Insecticidal soaps
-Plant-derived anti-desiccants and anti-transpirants
-Plant or microbe-derived products used to enhance plant growth and improve soil health
-Hydrogen peroxide
-Copper products (e.g., copper sulfate, copper sulfur)
-Sulfur
-Lime sulfur
-Neem products
-Refined (horticultural) oils used as dormant and growing season application
Prohibited
-All synthetic chemical fungicides
-Petrochemical based anti-desiccants
back to top
Rich Lassor had been working at a nursery in Great Barrington for seven years, when he was bit by the organic bug. 
Booklet - 
