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Diseases of vegetables

Diseases of vegetables. Megan Kennelly, Plant Pathology Hort 560, April 27 2006. Clemson University – USDA Cooperative Extension Slide Series, , www.ipmimages.org . Clemson University – USDA Cooperative Extension Slide Series www.ipmimages.org. Cabbage

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Diseases of vegetables

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  1. Diseases of vegetables Megan Kennelly, Plant Pathology Hort 560, April 27 2006 Clemson University – USDA Cooperative Extension Slide Series, , www.ipmimages.org Clemson University – USDA Cooperative Extension Slide Series www.ipmimages.org Cabbage white mold, mmk

  2. “What is wrong with my plant?” *Environmentalstress *Nutritional deficiency *Chemical injury *Insect damage *Infectious Disease: fungi, viruses, bacteria, nematodes Alternaria cabbage, mmk

  3. Abioticdiseases/disorders are caused by noninfectious agents such as weather stress, nutrient deficiency, chemical injury, soil factors… Two Types of Plant Disease Bioticdiseases/disorders are caused by infectious agents such as fungi, bacteria, viruses, nematodes

  4. Abiotic diseases Don’t spread from plant to plant (not infectious) Causes • Adverse environment • Mechanical and chemical injury • Adverse soil conditions • Soil structure • Soil fertility **Can predispose to biotic disease

  5. Kansas = Weather Stress Early spring, late fall frosts Heavy soils compaction Hot, cold, drought

  6. Nutrient Deficiencies Iron Magnesium Calcium Molybdenum

  7. Toxicities • Excessive salts • Chemical damage/drift • GH sample Phenoxy damage, NAT Tomato, tordon, NAT

  8. Biotic/infectious diseases: Disease triangle Pathogen fungi bacteria nematodes viruses Host Species Cultivar Age Environment Temp, RH, wetness

  9. Symptoms & Signs Symptom Expression of a disease by the plant Sign Visible presence of a pathogen

  10. Symptoms Leaf spots Mottling, distortion Galls http://www2.dpi.qld.gov.au/horticulture/17902.html Wilt

  11. Signs: pathogen structures Anthracnose Tomato Clemson University – USDA Cooperative Extension Slide Series www.ipmimages.org Anthracnose squash Clemson University – USDA Cooperative Extension Slide Series, , www.ipmimages.org Cabbage white mold mmk

  12. Bacterial wilt-cucurbits

  13. Infectious agents: pathogens Viruses Bacteria Fungi Nematodes most microbes are not pathogens

  14. Viruses DNA or RNA + protein Small genomes Disrupt normal cell metabolism Multiply only in live cells Spread: Insect, mechanical, seed, vegetative propagation

  15. Ring spots Wilt, decline, death Veinal chlorosis Mosaic & distortion TSWV Mottling & distortion Photos: Ned Tisserat

  16. Vectors: whiteflies, aphids, thrips Alton N. Sparks, Jr., The University of Georgia, www.ipmimages.org

  17. Bacteria Prokaryotes no nucleus plasmids binary fission ID: cultural, biochemical DNA Name changes Many symptoms: leaf spots,wilts rots, galls, blights Xanthomonas campestris—bacterial spot on pepper Volcani Center Archives, Bet Dagan, Israel, www.ipmimages.org

  18. Bacterial spread: Rainsplash Vectors Seed Vegetative propagation Black rot cabbage, MMK NAT

  19. Fungi and oomycetes • Most fungi and oomycetes dispersed by spores • Thread-like growth • Many kinds of symptoms

  20. A whale is not a fish, and an oomycete is not a fungus Oomycetes (water molds): Downy mildews (NOT powdery mildews) Phytophthora Pythium *implications for management

  21. Repeating cycle spores Winter spore/survival structure http://strawberry.ifas.ufl.edu/ BerryTimes/BVTDec04.htm

  22. Nematodes • Microscopic worms • Parasitic nematodes have stylet. • Most live in soil/roots. • Root deformity, stunting, yellowing, general decline Root-knot nematode on canteloupe DAFF Archives, , www.ipmimages.org

  23. Pathogen categories What kind of organism is it? What does it infect? Above-ground: leaves, stem, flower, fruit Below-ground: roots, tubers Crown Whole plant: wilts Tomato, sclerotinia NAT

  24. Above ground Bacterial spot, pepper

  25. Roots • Rots primarily caused by fungi and oomycetes, often found in wet soils/poor drainage Aster yellows, mmk

  26. “Damping off” of seedlings Pre-emergence: fungi infect germinating seeds Post-emergence: fungi infect stems near soil surface Pythium, Rhizoctonia

  27. Wilt Diseases • Pathogen systemically colonizes water conducting system • Infections usually result in death • Bacterial wilt of cucurbits • Verticillium wilt of numerous plants • Fusarium

  28. Possible clues Plant species, variety Planting date or age Weather/watering patterns Soil factors: drainage, compaction Chemical useage Spatial Distribution Timing

  29. Patterns in time… is it spreading? Lots of spots

  30. Plant Disease ID • Plant Disease Diagnostic Lab Kansas State University Throckmorton Hall Manhattan KS 66506 785-532-5810 Fees: $5 - $10 (County Extension Office) Bean Rust Clemson University – USDA Cooperative Extension Slide Series, , www.ipmimages.org

  31. Plant Sample Collection • Representative samples: ‘More is better!’ • Include roots! • ‘Healthy + Affected’ plants for comparison. • Immediately place in plastic bags. • No wet paper towels. • Keep it cool • Ship Monday – Wednesday. • Include lots of background information

  32. Management of diseases • Resistance • Cultural • Rotation, green manures • Clean planting material • Make site unfavorable to disease: spacing, staking, water management -Sanitation • Chemical • Non-conventional materials

  33. Integrated pest management “IPM is a systematic strategy for managing pests which considers prevention, avoidance, monitoring and suppression. Where chemical pesticides are necessary, a preference is given to materials and methods which maximize public safety and reduce environmental risk.” UMass

  34. EPA definition IPM is an effective and environmentally sensitive approach to pest management that relies on a combination of commonsense practices. IPM programs use current, comprehensive information on the life cycles of pests and their interactions with the environment. This information, in combination with available pest control methods, is used to manage pest damage by the most economical means, and with the least possible hazard to people, property, and the environment. IPM programs take advantage of all pest management options possibly including, but not limited to, the judicious use of pesticides.

  35. Sustainable USDA “Some terms defy definition. ‘Sustainable agriculture’ has become one of them. In such a quickly changing world, can anything be sustainable? What do we want to sustain? How can we implement such a nebulous goal? Is it too late? With the contradictions and questions have come a hard look at our present food production system and thoughtful evaluations of its future. If nothing else, the term ‘sustainable agriculture’ has provided ‘talking points,’ a sense of direction, and an urgency, that has sparked much excitement and innovative thinking in the agricultural world.”

  36. USDA The term sustainable agriculture means an integrated system of plant and animal production practices having a site-specific application that will, over the long term: *satisfy human food and fiber needs *enhance environmental quality and the natural resource base upon which the agricultural economy depends *make the most efficient use of nonrenewable resources and on-farm resources and integrate, where appropriate, natural biological cycles and controls *sustain the economic viability of farm operations enhance the quality of life for farmers and society as a whole."

  37. Certification programs Organic IPM/Eco/Reduced-risk

  38. Resistance Resistance can be major-gene (all or nothing) or “partial” or “quantitative” (more durable) Using resistant cultivars is critical first step in management Pathogens can overcome resistance genes

  39. Cultural: Rotation, green manures • Rotate to a non-host • Not possible with all diseases • Green manures: may suppress pathogen numbers • ex: brassicas and nematodes Rhizoctonia Clemson University – USDA Cooperative Extension Slide Series, , www.ipmimages.org

  40. Cultural: clean planting material Certified seed Treated seed Disease-free transplants Disease-free cuttings Sterile pots Sterile potting media/soil-less mix *ex: Pythium in field soil

  41. Cultural: site management Proper spacing Raised beds Water management drainage, drip irrigation contaminated water (P. capsici) Airflow (fans in greenhouse) Staking/trellising

  42. Cultural: sanitation Remove diseased material Control weeds may harbor pathogens or insect vectors Tillage: bury infected debris

  43. Chemicals Bactericides (mostly copper compounds) Fungicides (many kinds) Nematicides usually pre-plant fumigation APSnet.org MITC

  44. Chemicals The label is the law plants, diseases, sites, rates pre-harvest intervals re-entry intervals

  45. Chemicals Names can be tricky active ingredient: pyraclostrobin brands: Cabrio, Headline EC, Pristine

  46. Chemicals Contact/Protectants/ Pre-infection Do not penetrate the plant Need to be present before pathogen is there *Need good coverage Rain can wash it off Multi-site, low risk of resistance APSnet.org

  47. Chemicals Systemic/Post infection/Curative Penetrate the plant Move within plant (varies) Specific mode of action Resistance is more likely ex: powdery mildew Rotate different chemistries P mildew, squash Clemson University – USDA Cooperative Extension Slide Series, , www.ipmimages.org

  48. Chemicals www.greenbook.net Chemical names, brand names, label summary, the label itself, MSDS sheet, state registrations

  49. Alternatives/organic Biological controls antagonistic fungi, bacteria Green manures Plant growth promoters Compost teas Copper, sulfur, potassium bicarbonate Nysaes.cornell.edu http://grant-adams.wsu.edu

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