Biological control

1. Biological control Joyce E. Loper Research Plant Pathologist, USDA-Agricultural Research Service Professor (courtesy), Department of Botany and Plant Pathology loperj@science.oregonstate.edu 738-4057

2. Pathogen Host Environment The Plant Disease Triangle Take home message: Microorganisms, whether indigenous or introduced are an important component of the environment.

3. Biological control Reduction of the amount of inoculum or disease-producing activity of a pathogen accomplished by or through one or more organisms other than humans.

4. Biological control gained strength as a subdiscipline of Plant Pathology in the 1960s, when a group of scientists recognized that epidemics of soilborne plant diseases could not be understood without considering the the ecology of soil fungi and Oomycetes and the resident soil microflora.

5. Biological Control of Plant Diseases

6. Kinds of Biological Control • Conservation- cultural practices Suppressive soils General suppression Specific suppression • Classical– self sustaining following a single release of a “natural enemy” • Augmentative – periodic introduction to supplement natural reproduction Chestnut Blight and hypovirulence • Innudative– mass introduction of biocontrol agent Crown gall Heterobasion root rot Fire blight Postharvest diseases

7. Suppressive Soils • The pathogen does not establish or persist • The pathogen establishes but causes little or no disease

8. General Suppression field soil Disease severity sterilized soil Propagule level A fixed level of the pathogen causes less disease in the presence of indigenous soil organisms.

9. Take all of wheat caused by Gaeumannomyces graminis var tritici

11. Take-all decline with monoculture of wheat

13. Associating populations of organisms with soil suppression

14. Pseudomonas fluorescens produces an antibiotic that is toxic to the take-all pathogen

15. The antibiotic 2-4-diacetylphloroglucinol is toxic to the take-all pathogen O O O H H C C H 3 3 H O O H

16. Wheat seed treatment with Pseudomonas fluorescens for control of take-all No seed treatment Seed treatment with P.f. Seed treatment with mutant that does not produce an antibiotic

19. Borneman and Becker evaluated the Microorganisms associated with cysts in suppressive and conducive soils

20. Associating populations of organisms with soil suppression

22. Olatinwo, R., Borneman, J., and Becker, J. O. 2006. Induction of beetcyst nematode suppressiveness by the fungi Dactylella oviparasitica and Fusarium oxysporum in field microplots. Phytopathology 96:855-859.

23. Kinds of Biological Control • Conservation- cultural practices Suppressive soils General suppression Specific suppression • Classical– self sustaining following a single release of a “natural enemy” • Augmentative – periodic introduction to supplement natural reproduction Innudative– mass introduction of biocontrol agent Crown gall Heterobasion root rot Fire blight Postharvest diseases Chestnut Blight and hypovirulence

24. Biological control with Introduced Antagonists Biological control agent: Hypovirulent isolates of Cryphonectria parasitica Disease: Chestnut Blight Pathogen: Cryphonectria parasitica Mechanism: hypovirulence

26. History of the Chestnut Blight Pathogen in the United States

31. Transmission of hypovirulence decreases with diversity of vegetative compatibility groups in the pathogen population

32. Kinds of Biological Control • Conservation- cultural practices Suppressive soils General suppression Specific suppression • Classical– self sustaining following a single release of a “natural enemy” • Augmentative – periodic introduction to supplement natural reproduction Chestnut Blight and hypovirulence • Innudative– mass introduction of biocontrol agent Crown gall Heterobasion root rot Fire blight Postharvest diseases

33. Biological control with Introduced Antagonists Biological control agent: Agrobacterium radiobacter Disease: Crown gall Pathogen: Agrobacterium tumefaciens Mechanism: antibiosis

34. Crown gall caused by Agrobacterium tumefaciens

35. Infection by Agrobacterium tumefaciens Short period of Susceptibility: Wound typically heals over after about 24 hours and is no longer an opening for infection

36. In nurseries growing woody perennials, wounds are induced by root pruning. These can be treated with the biocontrol agent immediately

37. Untreated Treated with K84

38. Why does biological control of crown gall • work so well??? • Limited time of host susceptibility to disease • This means the biocontrol agent doesn’t • have to persist for a long time in the • environment • The infection court is defined and easily treated • This means the biocontrol agent can be • applied directly to the infection court, and doesn’t • Have to move there on its own • There are no chemical controls available • The sensitivity of the pathogen population can be predicted • For example, strains pathogenic to cherry are • sensitive to agrocin 84, whereas strains pathogenic • to apple are not uniformly sensitive.

39. Kinds of Biological Control • Conservation- Suppressive soils General suppression Specific suppression • Classical – self sustaining following a single release of a “natural enemy” • Augmentative – periodic introduction to supplement natural reproduction Chestnut Blight and hypovirulence • Innudative – mass introduction of biocontrol agent Crown gall Heterobasion root rot Fire blight Postharvest diseases

40. Heterobasidion root rot of pine • The fungus Heterobasidion annosum is the most damaging root pathogen of coniferous trees in the Northern hemisphere. • It progresses from the roots into the base of a tree, causing an economically important butt rot. • Once established in a site, the fungus is almost impossible to eradicate; it spreads progressively by contact of healthy roots with infected roots http://www.biology.ed.ac.uk/research/groups/jdeacon/microbes/heterob.htm

41. Fruiting bodies release air-borne basidiospores that can spread the infection to new sites. • Basidiospores land on freshly cut stump surfaces, and the fungus grows down through the stump tissues to the dead roots, from which it can infect the roots of adjacent healthy trees. http://www.biology.ed.ac.uk/research/groups/jdeacon/microbes/heterob.htm

42. Fresh pine stumps can be colonised by another fungus, Phlebiopsis gigantea (previously called Peniophora gigantea), which is weakly parasitic but poses no danger to healthy trees. • If Phlebiopsis is applied first then it can prevent invasion by H. annosum, protecting the stump surfaces without the need for phytotoxic chemicals. • P. gigantea is commercially available in Britain, Sweden, Norway, Switzerland and Finland, as either a spore suspension or a dry product (named "Rotstop"). • It was available in the USA until 1995 when the Environmental Protection Agency required it to be registered officially as a biological pesticide - a relatively expensive process that probably would not be cost-effective for the commercial producers. http://www.biology.ed.ac.uk/research/groups/jdeacon/microbes/heterob.htm http://www.nysaes.cornell.edu/ent/biocontrol/pathogens/p_gigantea.html

43. Kinds of Biological Control • Conservation- Suppressive soils General suppression Specific suppression • Classical – self sustaining following a single release of a “natural enemy” • Augmentative – periodic introduction to supplement natural reproduction Chestnut Blight and hypovirulence • Innudative – mass introduction of biocontrol agent Crown gall Heterobasion root rot Fire blight Postharvest diseases

44. Decay management product for • Citrus • Stone fruits • Pome fruits • Potatoes a.i.: Pseudomonas syringae - ESC-10: EcoScience strain - ESC-11: USDA strain

45. untreated Bio-Save

46. Why Postharvest Biocontrol? • Market need: • few labeled chemicals • fungicide resistance problem • System characteristics

47. chlorine spray Chlorine bath or spray bin dump

48. Clean Rinse or Fungicide Spray

49. fungicide in wax Wax application

50. Bio-Save Application