Classical Biological Control

The ecological response to

invasive insects and plants

Read chs 9 &11

Conceptual Model of Classical Biological Control

Goal is not reconstruction of the whole trophic superstructure, only transference of specialized

primary natural enemies

Many insect pests are nonnative species. In MA, 48% of pests of ornamental plants are invasive

Olive scale

Larch sawfly

CA red scale

Winter moth

90% control

99.9% control

99.9% control

95% control

How much are pest densities reduced by classical biological control of insects?

Date of natural enemyintroduction

Steps in Classical Biological Control

Research1.Target selection and taxonomy2. Foreign exploration3. Quarantine host range estimation4. Introduction and establishment5. Intensive and then wide evaluation6. Grower and public education

Extension

Example#1 of CBC:Ash whitefly in CA in

the 1990s

nymph

adult

Ash whitefly infested yard and street trees over thousands of square miles in southern California

Whiteflies reached high densities, covering all available leaf surfaces

Encarsia inaron, the aphelinid that completely controlled Ash whitefly in the United States

The parasitoid Encarsia inaron, introduced from Europe reduced the pest over 99.99% in 18 months

Example #2: Euonymous scale in MA

Euonymus scale is an Asian armored scale capable of killing ornamental euonymus plants in the landscape

Dead euonymus hedgekilled by scale

The imported natural enemies included the coccinellid Chilocorus kuwanae

Pupae

Larva adult

egg

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Natural enemies introduced against euonymus scale included the cybocephalid

Cybocephalus nr nipponicus

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Natural enemies introduced against euonymus scale included the aphelinid parasitoids in

Encarsia, Coccobius, and Aphytis

parasitoid

parasitoid

Numerous pupae and larvae of C. kuwanae on euonymus scale

Establishment and Spread-requires high population growth rate of natural enemy

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Documentation of spread of Chilocorus kuwanaeafter release– predator of euonymus scale

Dead euonymous hedgekilled by scale

Spread of natural enemies: % of euonymus in landscape with heavy scale infestations with Chilocorus kuwanae

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Spread of natural enemies% of euonymus in landscape with Chilocorus kuwanae

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Evaluation of Natural Enemy Impact- study sites for determination of effect of Chilocorus kuwanae

on euonymus scale

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Evaluation of Natural Enemy Impact- effect of Chilocorus kuwanae on euonymus scale,

Control Site- no predator release

Plant died in fall

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Evaluation of Natural Enemy Impact- effect of Chilocorus kuwanae on euonymus scale-Release site

Predator build up

Scale decline

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Predator build up

Scale decline

Evaluation of Natural Enemy Impact- effect of Chilocorus kuwanae on euonymus scale Release site

Predator build up

Scale decline

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Predator build up

Evaluation of Natural Enemy Impact- SUMMARY Effect of Chilocorus kuwanae on euonymus scale

averaged over all 28 research sites

Predator presentPredator absent

Conclusion: sites with increasing scale typically lacked the predator, while sites with the predator typically decreased in scale density

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Predator build up

Scale decline

Effect of physical size of area on speed of impact of Chilocorus kuwanae on euonymus scale. At a small

scale (apartment complex with shrubs dispersed over about 100 acres) control was seen in 1 year

Data are % of shrubs with various scale density (N= none, L= light, M= medium, H= heavy)

release

impact46.012.7

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Predator build up

For all MA, impact was detectable 4-5 years after release and but increased further by 13 years post release

2002 - 1119 38.5 38.8 11.1 11.6

20.9

13.7

11.6

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Predator build upPredator presentPredator absent

Economic evaluation of Natural Enemy Impact-Cohort study of effect of scale density on 1-yr plant

survival in the landscape

No effect for L or M, high impact H

3.0% 2.1% 4.2% 12.1%

Control value

Example #3: Cassava mealybug in Africa

Cassava roots Cassava mealybugPhenacoccus manihoti

Cassava in West Africa-staple for millions

Cassava roots Cassava mealybugPhenacoccus manihoti

Healthy cassava

Cassava tip killed by mealbugs

Cassava roots Cassava mealybugPhenacoccus manihotiHealthy

cassava

Cassava tip killed by mealbugsCassava belt is as big as the United States

Cassava mealybug invaded Africa in early 1970s, As it spread and reached high densities,

cassava yields plummeted

Cassava mealybug invaded Africa in early 1970s, As it spread and reached high densities,

cassava yields plummeted

The new species, later called P. manihoti, was found in subtropical Paraguay (red)

With financial support from international donors, a CBC program was instigated

Search at first concentrated on the full tropics because the pest was though to be P. herreni, but later was recognized as a new species

With financial support from international donors, a CBC program was instigated

With financial support from international donors, a CBC program was instigated

P. herreni is found in northern SA (yellow)

Example #2: Cassava mealybug in Africa

This parasitoid controlled the pest in Africa

Epidinocarsis lopesiEncyrtidae

Chemical check method

Decline due to onset of rainy season

Example #4: Cassava green mite in Africa

Cassava green mite and its damageMononychellus tanajoa

Cassava green mite also invaded Africa, causing important losses

Classical biological control of spider mites had never been done before

A massive search of phytoseiids associated with cassava in South America found over 60 species

Climate matching of infested areas of Africa and source areas in South America suggested 5 species for initial introduction

Among those introduced, one species, Typhlodromalus aripo, increased and controlled the pest

Typhlodromalus aripo, the phytoseiid that controlled cassava green mite in Africa

Typhlodromalus aripo was widely released and established, using an aerial release system to cover

roadless areas

Areas with T. aripoestablishment; cross hatched areas, releases made but est. not confirmed

Planes were used to release mites in roadless areas, dropping vials with that released threads that tangled in bushes. Mites exited vials by climbing on threads onto foliageVials exit from special tube

Release vials contained mites and threads

Typhlodromalus aripo controlled cassava green mite upon release and has continued to suppress it

Typhlodromalus aripo controlled cassava green mite in Africa and yields increased 32%

The value of control of cassava green mite in Africa by Typhlodromalus aripo has been over

$100,000,000 in West Africa alone

Example #5: Blue gum psyllid in California

Eucalyptus pulverulentais grown in CA for use in floral bouquets

Blue gum psyllids

feeding on species of

Eucalyptus

Many eucalypt insects are invading California where these trees are widely planted as exotics.

Control depends on releasing specific parasitoids.

Blue gum psyllid

Its parasitoidPsyllaephagus pilosus

Blue gum pysllid is not a pest in its native Australia

Example #5: Blue gum psyllid in California

Parasitoidbuild up

BC of blue gum psyllid in California

Parasitoid build up

Pre CBC pysllid #s

Post CBCpysllid #s

Economic of CBC of Blue gum psyllid in California

Prior to CBC, blue gum growers applied 3 pesticide applications per year at $45-100 / acre each

Example #6: Pathogen CBC control of mist flower in Hawaii

All dark is mist flower

All dark is mist flowerSmut-killed mist flower shrub

The white smut Entyloma ageratinae was the highly effective control agent

Close up of mist flower shoots infected by the white smut Entyloma ageratinae

See black marks on leaves

Dark green shrubs are goneReplaced by light green grass

Post CBC picture showing disappearance of most of the mist flower shrubs

Example #7: Control of waterhyacinth (Eichhornia crassipes) by two Neochetina weevils

N. eichhornia N. bruchi

Example #7: Control of waterhyacinth in LousianaControl of waterhyacinth (Eichhornia crassipes) by the weevils Neochetina bruchi and N. eichhorniae

Biological control of waterhyacinth in Lake Victoria in Africa

Before After