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Anissa Poleatewich PPATH 405 November 30, 2009

Introduction to biological control…pathogens have pests too!. Anissa Poleatewich PPATH 405 November 30, 2009. Today’s class will provide an introduction to biological control of plant pathogens and weeds. Organisms used for biocontrol. Modes of action. Production.

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Anissa Poleatewich PPATH 405 November 30, 2009

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  1. Introduction to biological control…pathogens have pests too! Anissa Poleatewich PPATH 405 November 30, 2009

  2. Today’s class will provide an introduction to biological control of plant pathogens and weeds Organisms used for biocontrol Modes of action Production

  3. Disease management is essential for maintenance of sustainable agricultural systems

  4. The goal of disease management is to reduce the harmful effects caused by a disease

  5. Disease management requires consideration of epidemiological principles Disease Progress Curve A: Disease in an unmanaged field B: Reduce primary inoculum C: Reduce rate of infection D: Combine B and C

  6. Disease management utilizes several approaches that collectively are effective Chemical Biological Cultural

  7. Several factors are reshaping the future of crop protection Food safety • Pesticide resistance Environmental concerns

  8. Where does biological control fit in? • Many pesticides used in conventional agriculture are not allowed in organic • Combinations with reduced rates of pesticides • Situations where no control is available

  9. Biological control can be used to suppress many types of pest organisms Weeds Plant pathogens Insects

  10. Biological control involves suppressing pest organisms with other organisms Definition: Suppression of the damaging activities of one organism by the activity of one or more other organisms Manipulate the microbial environment Make it less inhabitable for the pathogen • Favor biological control agent and disfavor the pathogen

  11. Biological control requires an integration of knowledge across many disciplines

  12. Biological control can target one or more parts of the disease triangle Make the environment less favorable to the pathogen Environment Reduce Disease • Plant Parasitize or inhibit pathogen growth Activate plant defenses Pathogen

  13. Pathogen BiocontrolAgent Host Environment

  14. Biological control is associated with many types of organisms….

  15. Biological control is associated with several types of ecological interactions….

  16. Biological control agents can be classified based on several properties…

  17. What types of biocontrol agents are used? • To manage disease • Avirulent pathogens • Non-pathogenic microbes • Natural compounds • To manage weeds • Pathogens

  18. Templeton, TeBeest, and Smith, 1984 Pathogens can be used to control weeds • Northern jointvetch (Aeschynomenevirginica) • Leguminous weed in rice and soybean fields • Reduces crop quality and yield • Seeds difficult to remove in milling

  19. Anthracnose Lesions found on Northern Jointvetch in 1969 • Colletotrichumgloeosporioidesf. sp. aeschynomene

  20. TeBeest and Templeton, 1985 The biocontrol is registered as the mycoherbicide “Lockdown” • Applied aerially to rice and soybeans • Powder rehydrated and suspended in sugar solution • Mycoherbicide mode of action • Spores germinate and produce appressoria • Mycelium ramifies, lesions develop  7-10 days

  21. Avirulent strains of pathogens can be used to suppress plant diseases Example….. Disease: Black rot of cabbage Pathogen: Xanthomonascampestrispv. campestris(Xcc) Avirulent strain lacks necessary virulence genes

  22. The avirulentXcc is applied to the plant before dawn and enters the hydathodes • Cabbage then inoculated with pathogen (Virulent Xcc) Cabbages with no biological control agent + virulent Xcc Cabbages colonized with avirulent Xcc + virulent Xcc

  23. Non-pathogenic microbes do not have the ability to cause disease on any plant • RootShield • Trichoderma harzianum • Sonata • Bacillus pumilis • Serenade • Bacillus subtilis Pathogenicity is the EXCEPTION Many microbes will not cause disease

  24. Naturally occurring compounds can also be used to manage plant diseases BION – salicylic acid derivative • Activates systemic acquired resistance (SAR) Known as “plant activators” • These compounds often INDUCE a plant defense response Salicylic Acid BION

  25. Several “plant activator” products are commercially available • Actigard • BION • Messenger • N-Hibit • ProAct

  26. How do biocontrol agents work? • Modes of action…. • Direct antagonism • Parasitism and predation • Indirect antagonism • Competition or competitive exclusion • Induction of host resistance • Mixed-path antagonism • Antibiotics and enzymes

  27. Parasitism: Direct interaction between the BCA and pathogen • Agent uses pathogen for nutrients http://floriculture.osu.edu/archive/sep99/biocon.html

  28. Competition: Biological control agent outcompetes pathogen for space or nutrients • Manage the ecological niche to make it unsuitable for the pathogen and favor the biocontrol agent

  29. Induced Resistance: turning on plant defenses • Presence of a microbes or chemical elicitor activates… • Biochemical pathways • SAR, PR proteins

  30. Antibiosis: Inhibit pathogen growth through the production of antimicrobial compounds • Antibiotic or toxin produced and excreted by BCA

  31. There are three approaches to biocontrol that differ in their release strategy • Classical • Release of exotic agents to control pest • Control determined by natural dispersal of agent • Bioherbicidal/Inundative • Natural enemy applied in a manner similar to a pesticide/fungicide/herbicide • Conservation • Manipulation of agricultural practices to enhance the impact of natural enemies

  32. Screening for biological control agents must be carefully planned • Selection of isolates in vitro • Dual culture technique • Generally poor predictors of field performance • Interactions on host • Growth room or greenhouse • Field experiments

  33. Production of biocontrol products can be completed in fermentation tanks • Liquid fermentation • Bacteria and certain fungi • Inexpensive, large scale production Semi-sold fermentation Fungi that do not sporulate or survive liquid culture

  34. Formulation of a biocontrol products helps the agent encounter hostile environment • Pelletiztion or Micro-encapsulation • Wettable powders • Adjuvants added to active ingredient WINDER et al, 2003

  35. Templeton, TeBeest, and Smith, 1984 What properties make a good biological control agent? • C. gloeosporioideswasideal for use as bioherbicide • Poor dissemination of inoculum • Highly selective • Genetically stable • Spores easily produced in submerged liquid fermentation • Disease development over wide range of conditions

  36. Biological control is a management option where one organism is used to suppress pests A wide range of microbes and compounds can be used Biocontrol agents often utilize more than one mode of action Questions? Logo

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