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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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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
Disease management is essential for maintenance of sustainable agricultural systems
The goal of disease management is to reduce the harmful effects caused by a disease
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
Disease management utilizes several approaches that collectively are effective Chemical Biological Cultural
Several factors are reshaping the future of crop protection Food safety • Pesticide resistance Environmental concerns
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
Biological control can be used to suppress many types of pest organisms Weeds Plant pathogens Insects
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
Biological control requires an integration of knowledge across many disciplines
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
Pathogen BiocontrolAgent Host Environment
Biological control is associated with many types of organisms….
Biological control is associated with several types of ecological interactions….
Biological control agents can be classified based on several properties…
What types of biocontrol agents are used? • To manage disease • Avirulent pathogens • Non-pathogenic microbes • Natural compounds • To manage weeds • Pathogens
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
Anthracnose Lesions found on Northern Jointvetch in 1969 • Colletotrichumgloeosporioidesf. sp. aeschynomene
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
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
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
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
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
Several “plant activator” products are commercially available • Actigard • BION • Messenger • N-Hibit • ProAct
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
Parasitism: Direct interaction between the BCA and pathogen • Agent uses pathogen for nutrients http://floriculture.osu.edu/archive/sep99/biocon.html
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
Induced Resistance: turning on plant defenses • Presence of a microbes or chemical elicitor activates… • Biochemical pathways • SAR, PR proteins
Antibiosis: Inhibit pathogen growth through the production of antimicrobial compounds • Antibiotic or toxin produced and excreted by BCA
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
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
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
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
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
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