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

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

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.

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.

Biological Control of Plant Diseases

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

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

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.

Take all of wheat caused by Gaeumannomyces graminis var tritici

Take-all decline with monoculture of wheat

Associating populations of organisms with soil suppression

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

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

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

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

Associating populations of organisms with soil suppression

Olatinwo, R. , Borneman, J. , and Becker, J. O. 2006 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.

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

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

History of the Chestnut Blight Pathogen in the United States

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

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

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

Agrobacterium tumefaciens Crown gall caused by Agrobacterium tumefaciens

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

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

Treated with K84 Untreated

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.

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

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

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

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

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

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

untreated Bio-Save

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

Chlorine bath or spray bin dump chlorine spray

Clean Rinse or Fungicide Spray

Wax application fungicide in wax

Bio-Save Application

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: 244-249.

Biological control: Not just a bug in a bag!

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