Integrated Disease Management (IDM) is a concept derived from the successful Integrated Pest Management (IPM) systems developed by entomologists for insect and mite control. In most cases IDM consists of scouting with timely application of a combination of strategies and tactics.
Disease resistance conferred by a single major gene is sometimes called specific or qualitative resistance and is race-specific. This type of resistance is often unstable, and emergence of a pathogenic race that can attack that genotype can completely overcome this type of resistance. Quantitative resistance or general resistance derives from many different genes for resistance with additive effects to provide more stable (or durable) resistance to pathogens.
Development of resistance has been most successful against the more specialized pathogens such as rust fungi, smut fungi, powdery mildew fungi, and viruses, but less so against general pathogens such as many blight, canker, root rot and leaf spotting pathogens.
Disease escape occurs when susceptible plants do not become diseased for some reason. This may be due to some anatomical or physical character, such as the occurrence of leaf hairs, thick cuticle, or modified stomata, or they may be environmental, in which conditions are not conducive to disease development.
Hybridization is a tactic where a plant having the desired agronomic or horticultural qualities, but is susceptible to a disease, is crossed with a plant that is resistant but which may or may not have the other desirable characteristics such as size, yield, flavor, aesthetics, etc.
Selection of resistant plants involves subjecting plants to high levels of disease pressure, and using the surviving plants as sources of disease resistance.
Resistant plants are usually derived by standard breeding procedures of selection and/or hybridization.
Use of disease-resistant plants is the ideal method to manage plant diseases, if plants of satisfactory quality and adapted to the growing region with adequate levels of durable resistance are available.
Biological control involves the use of one living organism to control another, and this management technology has received much attention in recent times.
Many cultural practices can be modified to manage the occurrence, intensity or severity of plant diseases.
[The Protection Principle] depends on establishing a barrier between the pathogen and the host plant or the susceptible part of the host plant. It is usually thought of as a chemical barrier, e.g., a fungicide, bactericide or nematicide, but it can also be a physical, spatial, or temporal barrier.
Crop rotation is a frequently used strategy to reduce the quantity of a pathogen, usually soil-borne organisms, in a cropping area.
Soil fumigation has been a widely used eradication strategy. This technology involves introducing gas-forming chemicals such as carbon disulfide, methyl bromide, or chloropicrin into soil to kill target pathogens. However, undesirable side effects such as killing beneficial organisms, contamination of groundwater, and toxicity of these chemicals have resulted in less reliance on this approach for disease management.
[The Eradication Principle] aims at eliminating a pathogen after it is introduced into an area but before it has become well established or widely spread.
[Exclusion Principle] is defined as any measure that prevents the introduction of a disease-causing agent (pathogen) into a region, farm, or planting. The basic strategy assumes that most pathogens can travel only short distances without the aid of some other agent such as humans or other vector, and that natural barriers like oceans, deserts, and mountains create obstacles to their natural spread.
The first principle (prevention) includes disease management tactics applied before infection (i.e., the plant is protected from disease), the second principle (therapy or curative action) functions with any measure applied after the plant is infected (i.e., the plant is treated for the disease).
Plant disease management practices rely on anticipating occurrence of disease and attacking vulnerable points in the disease cycle (i.e., weak links in the infection chain). Therefore, correct diagnosis of a disease is necessary to identify the pathogen, which is the real target of any disease management program.
The goal of plant disease management is to reduce the economic and aesthetic damage caused by plant diseases.
Quarantine is often the best method for combating disease.
The cost to the US for introduced species is in excess of $137 billion.
Despite our best efforts new diseases are introduced and because our plants have little resistance to introduced species and there are no competitors or predators to keep their numbers low, and a epidemic occurs which is very difficult to control.
Epidemics of introduced (invasive) species are more severe than epidemics of endemic species.
Wood decay organisms result in wind damage and breakage in trees.
Inoculum can be fungal spores or survival structures, bacteria, or virus particles, but it can also be plant debris, infested soil, infected roots, diseased parts of perennial plants, insect vectors or infected fruit or vegetative organs.
Inoculum is the pathogen or its parts which can cause plant infection.
A major approach to disease control is inoculum reduction.
Epidemiology is the study of factors affecting the outbreak and spread of infectious disease. Familiarity with the epidemiology of a pathogen will show how factors such as temperature, rainfall, wind and leaf wetness affect its ability to produce spores, spread and infect its host.
The realistic way to manage plant disease is through an integrated management strategy that includes: 1) cultural practices, 2) epidemiology, 3) resistant varieties, 4) chemical pesticides, and 5) biological control.
Overwatered plants often become more susceptible to root rot fungi such as Phytophthora and Pythium. Underwatering plants appears to make them less able to fight off invading pathogens and drought stressed plants are more susceptible to cankers caused by Botryosphaeria (Fusicoccum) and Hendersonula.
Predisposition is the environmental modification of plant resistance making the plant more susceptible to disease.
Overwatering and underwatering plants both exacerbate disease.
High levels of nitrogen fertilizers, which result in rapid growth of plants, is often prescribed to improve plant health. Not only does this commonly result in ammonia toxicity, but high levels of nitrogen are known to exacerbate disease by many pathogens such as Rhizoctonia, Pythium, Phytophthora, Fusarium, Armillaria, Sclerotium, Pseudomonas, Corynebacterium, powdery mildews, rusts, cyst nematodes and many others.
Conditions which favor plant growth and health commonly favor disease.
Disease results from an interaction of the virulence of the pathogen, susceptibility of the host, and the conduciveness of the environment.
Cankers are a fourth type of disease which are usually characterized by conspicuous lesions on the stem or branches. This type of disease does not interfere with the water movement in a plant but with the movement of sugars and other substances in the phloem.
More often than not if the plant suddenly wilts or shows symptoms on all leaves the disease is caused by either a blockage in the water conducting vessels, which is called a “wilt disease” or it is caused by a “root rot disease”.
How the disease affects a plant and what organs it causes to malfunction can aid in the diagnoses and control of plant diseases... Leaf diseases are commonly associated with necrotic spots and/or signs of the disease such as spores or fruiting bodies of the attacking fungus.
For ornamental plants the Plant Pathologist must first examine such abiotic diseases as: 1) high or low temperatures, 2) excess or deficiency of water, 3) excess or deficiency of light, 4) lack of oxygen, 5) air pollution, 6) nutrient deficiencies, 7) mineral toxicities, 8) soil alkalinity or acidity, 9) toxicity of pesticides, 10) improper cultural practices and 11) lightening, before suspecting that the disease is caused by an organism.
Disease is a malfunctioning of a plant, which results from a continuous irritant by a pathogenic agent.
Plant pathology is the study of plant disease and the pathogens that cause disease. By its nature, plant pathology is a multidisciplinary field that integrates microbiology, plant science, environmental science and other disciplines.