Lecture insect disease - Use of Fungi for Insect Control pps

Agriculture andAgri-Food Canada Agriculture et Agroalimentaire Canada • Mostly obligate pathogens • Sexual & asexual spores • Spores ejected forcibly • Mostly restricted host ranges... A

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Use of Fungi for Insect Control

- Issues, Developments & Research Needs

Mark Goettel

Agriculture and Agri-Food Canada

Research Centre, Lethbridge, AB

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Agriculture and

Agri-Food Canada

Agriculture et Agroalimentaire Canada

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Agriculture and

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Division Chytridiomycota

• Genera Coelomomyces

• Pathogen of aquatic Diptera

• Obligate pathogens

• Require alternate crustacean hosts

• Very host specific

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Agriculture and

• Mostly obligate pathogens

• Sexual & asexual spores

• Spores ejected forcibly

• Mostly restricted host ranges

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Division Ascomycota

• Order Clavicipitales

• Genera: Cordyceps, Torrubiella

– Teleomorphic (sexual) state of many spp within Deuteromycota

• Order Ascosphaerales

– Genera: Ascosphaera

– Mostly obligate pathogens – Sexual & asexual spores – Mostly restricted host ranges

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Agriculture and

Division Deuteromycota

• Genera: Aschersonia, Aspergillus,

Beauveria, Hirsutella, Metarhizium,

Nomuraea, Paecilomyces, Verticillium(Lecanicillium)

• Most? anamorphic (asexual) state ofCordyceps

• Mostly facultative pathogen

• Assexual, immotile spores, conidia

• Mostly wider host ranges

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Some examples

Aschersonia aleyrodis Cordyceps

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Agriculture and

Metarhizium flavoviride Hirsutella

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Metarhizium anisopliae

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Agriculture and

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• Infection via externalintegument

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Agriculture and

• “Wider” host range

• Better suited for

• “Narrow” host range

• Better suited in classical approach

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Types of pathogens

• Strong

dose-mortality relationship

environmental factors

• Closely adapted to host

• Great potential for epizootics

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Agriculture and

Use of fungi

• Classical (introduction)

• Conservation

• Augmentation (insecticidal)

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• Competition with chemicals

• Takeovers and failures

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1996 1993

1996

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What is available worldwide?

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Agriculture and

• Beauveria bassiana

• Botanigard (Emerald)

• Naturalis-L (TroyBiosciences)

• Whitefly, thrips, aphidsand mealybugs

• Registered in USA,Mexico and SouthAmerican countries

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• Metarhizium anisopliae

• Bio 1020 (Bayer AG)

• New Bio 1020(Taensa)

• Black vine weevil

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Agriculture and

• Registered in Europe andUSA

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• Applied on “1000’s ofhectares”

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Agriculture and

Innovative application:

thinking outside of the box!

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Innovation

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Agriculture and

What is available in Canada?

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Nothing!

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Agriculture and

Why aren’t they available?

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Classical control

• Worldwide, between 1888 and 1992

• > 5,500 programs with parasitoids &predators

• < 50 programs with pathogens

• Why?

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Agriculture and

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Classical control

• Fungi

• Entomophaga maimaiga

against Gypsy moth in North America

• Zoophthora radicans against the

spotted alfalfa aphid

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Agriculture and

• Gypsy moth

• Accidental introduction in late 1800’s

• Devastated hardwood forests, billions $$ damage

• Entomophaga maimaiga

• First introduced from Japan in 1909

• Not observed until 1989

• Since then epizootics have swept most of North America

• Insecticide spraying no longer necessary

• Result of original introduction or accidental reintroduction?

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• Zoophthora radicans

• Introduction of strain from Israel into Australia in early 1980’s

• Alfalfa aphid

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Agriculture and

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Agriculture and

• Mortality over 90%

• Populations controlled

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• Do not spray insecticide if epizootic is

imminent (Arizona against cotton aphid)

• Do not apply fungicides (aphids in

greenhouses)

• Do not mow grass edges around onionfields (Onion maggots in Michigan)

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Agriculture and

Safety and Registration

• Vertebrate safety essential

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Direct infection of non-target hosts

• Host range

• Physiological host range

– ability to infect under “optimal”

“maximum challenge” conditions

• Ecological host range

– host range manifested under fieldconditions

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Agriculture and

Direct infection of non-target

hosts

• Knowledge of physiological host range

used to predict ecological host range

• Typical that hosts can be infected in the

laboratory that are never found infected inthe field

• due to complex biotic and abiotic

interactions that occur in the field

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Direct infection of non-target hosts

• Mortality

• Most typical measure of virulence

• Sublethal effects

• Reduced food consumption

• Reduced adult longevity

• Reduced fecundity

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Agriculture and

Indirect effects on

non-targets

• Difficult to predict

• Require long-term monitoring

• Example: Applications of B thuringiensisagainst Gypsy moth (Weseloh et al., 1983)

• Sublethal effect of exposure was

prolonged development of target host

• Longer susceptible period to parasitoid

• Increase in parasitoid populations in

treated plots

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Inundative application of

indigenous pathogens

• All organisms in area of application

potentially exposed to high concentrations

of the pathogen; higher than “natural”

• Could directly affect species not

normally affected by the pathogen

• Effect usually much, much less drasticwhen compared to chemical application

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Agriculture and

• Potential that the pathogen would becomenewly established within an NTO

population and spread within this

population is quite remote

• After application, inoculum levels usuallyrapidly return to pre-application levels

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Agriculture and

• Emphasis should be placed on pathogen’spersistence rather than host-range

• If negative impacts on NTO’s are

demonstrated, then use of the pathogencan be altered or discontinued

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Classical biocontrol

• Aimed at permanent establishment of anexotic agent in a new area

• Goal that it will persist and spread

• Can be used against introduced or

indigenous pest

• Knowledge of potential effects on NTO’s

is critical prior to release

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Agriculture and

• Physiological host range

• Evaluated under laboratory conditions

• Emphasis should be placed on those

organisms living in the same habitatswithin an ecosystem as the target pest

• Emphasis be placed on ability of

pathogen to become established withinNTO populations

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• Ecological host range

• Can be determined definitively only afterrelease of the pathogen

• Much useful information can be gained

by studying epizootiology of thepathogen in its area of endemnicity–Host range, persistence, climaticconstraints etc

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Agriculture and

• Studies in area of endemnicity a challengebecause because levels of both pathogenand host are often low

• Important to consider effects of depletion

of the target population on NTO’s

especially if the target population is

endemic (e.g E praxibuli & grasshoppers

in N.A.)

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• Studies of indirect effects

• Especially difficult

• Require thorough knowledge of the

target insect’s ecology and role in foodchains

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Agriculture and

Inundative application of indigenous pathogens

non-• Non-indigenous pathogens have potential

to establish, consequently risks could besimilar to those in classical biocontrol

• Most pathogens developed for microbialcontrol are ubiquitous

• Differences between strains and

pathotypes need to be considered

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• Potential effects can only be definitively

determined once the pathogen has beenreleased

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Agriculture and

Genetically modified

pathogens

• Potential risks include

• Transfer of genetic material to othermicrobes

• Increased host range

• Irreversible depletion of target host

• Competitive displacement of parentstrain

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Genetically-altered pathogens

• Risk assessment based on

• Biology and ecology of parent strain

• Nature of the introduced traits

• Laboratory & microcosm studies

• Persistence

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Agriculture and

Methods for non-target

evaluation

• Inclusion of controls in all assessments

• Positive controls (inoculated susceptiblehosts)

• Negative controls (non-inoculated,

susceptible hosts)

• Negative controls (inoculated target hosts)

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non-Methods for non-target

evaluation

• Laboratory evaluations

• Host range studies

• NTO’s potentially present in the targethost habitat

• choice of dose to approximate field

exposure levels

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Agriculture and

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– Field cages and containment methods

– Laboratory incubation of field-collected organisms

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Agriculture and

evaluation

• Field evaluations

• Provide most useful and definitive

information

• Require precise pathogen identification

• Require methods for rapid disease

diagnosis

• Require methods for estimation on

effects to non-target host populations

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Methods for non-target evaluation

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Agriculture and

Regulations

• Host range

• Detailed protocols on non-target testing

– Even for indigenous strains

• Classical biocontrol

• Firm guidelines for release of

non-indigenous entomopathogens generallynot available

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Agriculture and

• As new field diagnostic methods are beingdeveloped, it is becoming possible to

evaluate affects of pathogens

economically under field conditions

• Increased knowledge of pathogen

taxonomy, biology and epizootiology

should allow for more useful and better

risk assessments in the future

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My philosophy

• Priorities

• Get products already registered

elsewhere onto Canadian Market– Ensure they will be efficacious -registration does not necessarily meanuseful product

• Until this is done, development of newproducts remains of lower priority

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Agriculture and

My philosophy

• Priorities

• Discover and develop new products

– Much research beforecommercialization stage

• Adoption of microbials will requireparadigm shift

– Biodiversity important

– 100% production efficacyunreasonable

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It is logical.

Tiêu đề	Use of fungi for insect control - Issues, developments & research needs
Tác giả	Mark Goettel
Trường học	Agriculture and Agri-Food Canada
Chuyên ngành	Entomology
Thể loại	Bài viết
Thành phố	Lethbridge

Định dạng
Số trang	67
Dung lượng	1,97 MB