1. Biological control Joyce E. Loper
Research Plant Pathologist, USDA-Agricultural Research Service
Professor (courtesy), Department of Botany and Plant Pathology

2. The Plant Disease Triangle
Pathogen
Host
Environment
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 A fixed level of the pathogen causes less disease
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 pathogen3 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
Olatinwo, R., Borneman, J., and Becker, J. O Induction of beetcyst
nematode suppressiveness by the fungi Dactylella oviparasitica and
Fusarium oxysporum in field microplots. Phytopathology 96:

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. Agrobacterium tumefaciens
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. Treated with K84
Untreated

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

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.

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.

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
Pseudomonas syringae strain ESC-10 (006441) Pseudomonas syringae strain ESC-11 (006451) Pseudomonas syringae strain ESC-10 and Pseudomonas syringae strain ESC-11 are natural strains of bacteria that occur on many kinds of plants throughout the world. They were originally isolated and identified from apples. They are applied to certain fruits before storage in order to protect the fruits from several fungal diseases. Although the exact method of disease control is unknown, these harmless bacteria probably outcompete the fungi for space and nutrients on the fruit, thereby preventing the fruit from rotting before it can be used. Application Methods: After the fruit is harvested and cleaned, its surface is exposed to a solution containing the ESC-10 or ESC-11 bacterium. The pesticide applicator can apply the solution by spraying, or by dipping the fruit into the solution. These applications are considered indoor uses, since they take place in enclosed areas. EcoScience BIOSAVE 10LP, BIO-SAVE 11 LP JET HARVEST
Q. What is the difference between Bio-Save®100, Bio-Save®110 and Bio-Save®1000 and Bio-Save® 10 LP? Which one should I use?
A. The active ingredient in all three products is Pseudomonas syringae. But the Pseudomonas syringae isolates differ in their ability to protect produce from diseases. At this time it appears Bio-Save®100 is more effective controlling apple disease, Bio-Save®110 is more effective controlling disease in pears and potatoes, and Bio-Save® 1000 is best on citrus, cherries and potatoes. Bio-Save® 10 LP is a replacement for the Bio-Save® 100 and Bio-Save® 1000.
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 bath or spray
bin dump
chlorine spray

48. Clean Rinse or Fungicide Spray

49. Wax application
fungicide in wax

50. Bio-Save Application

51. Usage History of Bio-Save by Crop
5,000,000
2,000,000
4,000,000
6,000,000
8,000,000
10,000,000
Cartons
Pear and Apple
4,000,000
Cartons
3,000,000
2,000,000
Citrus
1,000,000
4,000,000
Cherry
Potato
8,000,000
3,000,000
6,000,000
Sacks
Lugs
2,000,000
4,000,000
Pear market downtrending because of the introduction of two new chemicals.
Citrus' steady decline due to lack of market presence without direct representation and/or distribution.
Potato industry gaining large acceptance for Bio-Save through sales and awareness with quality yearly performance.
Sweet potato market will be new this year with excellent testing on Rhizopus soft rot. Distribution set-up in North Carolina.
1,000,000
2,000,000
1999
2000
2001
2002
2003
2004
2005
1999
2000
2001
2002
2003
2004
2005
From Stockwell and Slack. Phytopathology 97:

52. Biological control:
Not just a bug in a bag!

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