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Organic disease management
- 1. Disease Management Terry Kirkpatrick, Plant Pathology M. Elena Garcia, Horticulture University of Arkansas
- 2. Plant Disease A malfunction of one or more plant systems due to continuous irritation that results in some symptom – Horsfall &Cowling, 1977
- 3. At least 90% of plant disease control is accomplished through proper cultural methods and sanitation. Unfortunately, modern agriculture sometimes ignores the fundamental concepts for convenience.
- 4. Types of Diseases Biotic: result of infection of plant by a pathogen; able to spread to healthy plants Types of pathogens: fungi, bacteria, viruses, nematodes, parasitic plants Abiotic: result of environmental or cultural problem; cannot be transmitted Types: light, temperature, hail, lightning, fire, wire girdling, pot-bound roots, air pollution, chemical injury, herbicide injury, nutrient deficiencies, chemical toxicity
- 5. Biotic Diseases Fungi ------ ~80% Bacteria ----- ~15% Nematodes ----- <5% Viruses ------ <5%
- 6. The Disease Triangle Disease development depends on: 1. Presence of pathogen (source of inoculum) 2. Host- Plant susceptibility 3. Environmental conditions must be favorable (light, moisture, temperature, soil fertility)HOST Total of conditions favoring susceptibility Amount of disease
- 7. HOST Immune-no association other than coincidental causal entity (pathogen) has no effect. Susceptible – unable to suppress a pathogen; adverse response of plant to causal organism Resistant-ability to suppress the activity of a pathogen; may or may not have adverse effect on plant. Susceptible Resistant
- 8. Pathogen – an organism that is capable of causing disease Virulent Avirulent Virulence – relative ability of the pathogen to cause disease Avirulence – inability of a pathogen to cause disease In order for disease to occur, both a susceptible host and a virulent pathogen must be present
- 9. Environmental Manipulation Environment Host Pathogen You can’t control the weather…… But you can control the plant’s environment, at least to some degree
- 10. Environmental management for disease control • Irrigation: availability; quality; type • Site selection • Pruning; thinning; trellising; plant spacing; row spacing • Beds vs. flat planting • Annual vs. perennial (strawberry) • Mulching • Fertility; pH; overall plant nutrition balanced • Timely harvest
- 11. How do diseases Spread? Soil-borne diseases Wind-borne diseases Seed-borne diseases Vector-transmitted diseases
- 12. Soil-Borne Diseases Introduced into soil Inoculation Wind Infected seeds Infected transplants Other infected plants Contaminated tools Water Crop residues provide an environment for pathogen Can affect roots or any part of the plant Smut, bacterial wilt, fusarium wilt, dampening-off
- 13. Wind-Borne Diseases Spore transportation May be great distances Transport directly to aerial potions of plants Inoculate soil Rusts, powdery mildew, late and early blight of tomato, apple scab
- 14. Seed-Borne Diseases Recommended to purchase certified disease-free seeds Seed sterilization Bacterial blights and anthracnose of peas Potato ‘seeds’ Viral diseases may spread by seeds
- 15. Vector-Transmitted Diseases Insects Carried from plant to plant on the mouth parts of insects People Pruning Nematodes Fungi
- 16. Epidemiology 1. Single cyclic disease – most soilborne pathogens. 0 10 20 30 40 50 60 70 Disease Time
- 17. Epidemiology 1. Multicyclic disease – Foliar pathogens 0 10 20 30 40 50 60 70 80 90 100 Disease Time lag exponential stationary Moisture on foliage is a primary factor.
- 18. Symptoms caused by fungi: May be local or general Necrotic symptoms Leaf spots Blight Canker Dieback Root rot Damping-off Basal stem rot Soft or dry rot Anthracnose Scab Decline Excessive growth symptoms Clubroot Galls Warts Witches’ brooms Leaf curls Additional symptoms Wilt Rust Smut Mildew
- 19. Fungal Symptoms Anthracnose- Pumpkin Anthracnose- Strawberry Sherrie Smith, University of Arkansas, Cooperative Extension Sherrie Smith, University of Arkansas, Cooperative
- 20. Symptoms caused by bacteria: Galls: crown, twig, or cane Hairy root Soft rots Cankers Wilt Scab Blight Leaf spots Root nodules of legumes Fire blight Sherrie Smith, University of Arkansas Cooperative Extension
- 21. Bacterial Symptoms Watermelon Bacterial Fruit Blotch Sherrie Smith, University of Arkansas, Cooperative Extension Cabbage Black Rot
- 22. Symptoms caused by viruses: May occur on any part of plant Stunting Premature death Mosaics Mottling Streak Ring or line pattern Vein clearing Vein banding Chlorotic spots Ring spots APLPV - American Plum Line Pattern Virus - Plums Sherrie Smith - University of Arkansas, Cooperative Extension
- 23. Pictures of Viral Symptoms Bean- Yellow Mosaic Virus Tomato-Tobacco Mosaic http://www.avrdc.org/LC/tomato/tomv/html Sherrie Smith, University of Arkansas, Cooperative Extension
- 24. Some Symptoms caused abiotic diseases: Low temperature Late frost tip or bloom necrosis Bark split Internal branch necrosis Winter drying of evergreens Cold water rings Leaf margin necrosis Frost injury to fruits High temperature Sunscald on fruit Water core Blossom end rot (citrus) Light Etiolation (low light) Scald (high light) Low moisture Leaf scorch Wilting High moisture Flood damage Oedema Rot Low oxygen Black heart of tubers
- 25. Some Symptoms caused abiotic diseases: Herbicide injury Leaf or fruit deformities Chlorosis Necrosis Stunting Death Air pollution Chlorosis Bleached leaves Stunting Leaf margin necrosis Premature defoliation Sherrie Smith, University of Arkansas, Cooperative Extension Photo courtesy NARA, photographer Gene Daniels/U.S. EPA Ozone-damaged plant (left) and normal plant (right)Grazon Damage
- 26. Managing Plant Diseases Manage cropping system in a way that prevents disease from occurring Identify disease Biotic or abiotic Fungi, bacteria, virus, or nematode Foliar or soil-borne Take disease triangle into consideration: Improve quality and ability of host to withstand disease Reduce or eliminate populations of pathogens Encourage environmental conditions favorable for hosts and unfavorable for pathogens
- 27. Why is Disease ID Important? Altering irrigation system to reduce leaf wetness will help against foliar disease, but not soil-borne disease Crop rotations affect soil-borne disease, but not wind- or insect-dispersed diseases Fungicides control fungal disease, but not viruses
- 28. Sanitation: A Key Strategy to Disease Prevention Plant in sites free of disease Clean equipment to prevent spread of disease through fields Clean pruning tools in 10% bleach solution between cuts Remove crop residue to reduce inoculum buildup Remove weeds that may serve as pathogen host Prune diseased portion from plants Remove severely infected plants from field Prevent further spread of viruses Properly dispose of infected debris Place infected debris in center of hot compost heap Burn debris Place in sealed container in trash
- 29. Cultural Practices to Improve Host Health Choose resistant cultivars Avoid excess or deficient crop nutrition Use transplants rather than seeds to avoid exposure to soil-borne seedling diseases Plant seeds shallowly to limit pathogen exposure Correctly prune woody plants to improve air circulation and light infiltration Scab resistant apple cultivar ‘Liberty’ (left) with susceptible cultivar ‘McIntosh’ (right)
- 30. Cultural Practices that may reduce pathogen presence Adjust soil pH Liming negatively affects some fungal pathogens (e.g. club root ) Increasing pH inhibits survival of some bacteria (e.g. scab, cotton root rot) Prune out diseased portion of plants to avoid further spread Crop rotations break cycle of certain pathogens Spatially: move location of species within field Temporally: grow different species from year to year Keep in mind many pathogens attack numerous species within a plant family
- 31. Cultural Practices that affect environmental conditions Use appropriate types of irrigation Overhead irrigation encourages spread of foliar disease Avoid overwatering Improve soil drainage Improve air circulation through wider row spacing, decreased planting density, and pruning Time tasks appropriately Cool soils slow germination of many seeds (e.g. corn, beans), increasing susceptibility to soil-borne disease Late-season pruning or fertilization discourages hardening-off, increasing occurrence of abiotic disease (e.g frost injury) Post-harvest cold storage to delay growth of soft rots
- 32. Physical Control Soil solarization Increased temperatures due to solar heat kill many soil-borne pathogens near soil surface Cover soil with clear plastic Soil temperatures may reach 52°C
- 33. Biological Control Limited options for disease control Increase diversity of soil microbes through proper soil management and addition of organic matter Cross-protection Inoculation of plant with mild strain of disease to provide protection against more virulent strains Example: Galltrol-A®; nonpathogenic strain of Agrobacterium; protects against crown gall Coniothyrium minitans Fungal pathogen of Sclerotinia sclerotiorum and S. minor (cause of white mold on cole crops, carrots, and beans OMRI-Listed product: Contans® WG Other control
- 34. Chemical Control Potassium-, Sodium-, or Aluminum- Bicarbonates Formulations differ in efficacy against certain diseases (e.g. Potassium bicarbonate more effective in control of powdery mildew) Studies have found a variety of concentrations most effective, ranging from 0.5-2% Some benefit seen from addition of surfactants Foliar burning resulted when concentration too high OMRI-Listed products: Kaligreen® and MilStop® broad spectrum foliar fungicide
- 35. Chemical Control Sulfur : prevents fungal spores from germinating; phytotoxic Also has some insecticidal and acaricidal properties Toxic to beneficial insects, fish, mammals Should not be used if oil has been sprayed in the previous month
- 36. Chemical Control Lime-sulfur: kills recently germinated fungal spores phytotoxic Spraying during high temperatures (>85F) increases phytotoxicity Toxic to mammals Copper: inhibit growth and germination of spores phytotoxic Labeled for use on over 100 crops to control fungal and bacterial diseases Should be used with care due to toxicity to several non-target species OMRI-Listed products: Champion WP ®, Crop Clean COCS ®, Britz Copper Sulfur 15-25 Dust ®, Nordox 75WG ®, Concern® Copper soap Fungicide, Cueva Fungicide Concentrate ®, Cueva Fungicide Ready to Use ®, Lilly Miller Ready to Use Cueva Copper Soap Fungicide®
- 38. Acknowledgements This presentation address general organic production practices. It is to be to use in planning and conducting organic horticulture trainings. The presentation is part of project funded by a Southern SARE PDP titled “Building Organic Agriculture Extension Training Capacity in the Southeast” Project Collaborators • Elena Garcia, University of Arkansas CES Heather Friedrich, University of Arkansas Obadiah Njue, University of Arkansas at Pine Bluff Jeanine Davis, North Carolina State University Geoff Zehnder, Clemson University Charles Mitchell, Auburn University Rufina Ward, Alabama A&M University Ken Ward, Alabama A&M University Karen Wynne, Alabama Sustainable Agriculture Network