Ed Baker

PHASMIDS AS PESTS OF AGRICULTURE

AND FORESTRY

USA (1870s-1970s)Diapheromera femorata

AUSTRALIA (1880s-1980s)Didymuria violescensPodacanthus wilkinsoniAnchiale austrotessalata

FIJI (1920s-Present)Graeffea crouanii

CHINA (1980s-Present)Various spp.

MAJOR INFESTATIONS

REVIEW OF DIAPHEROMERA

“…eggs and fecal pellets are dropped to the ground in great numbers, producing

a pattering sound, like rain, accompanied by a peculiar seething

sound of thousands of jaws chewing the leaves.”

- Helfer (1963)

REVIEW OF DIAPHEROMERA

REVIEW OF DIAPHEROMERA

New York Outbreak (1870s)

Wisconsin Outbreak (1959-60s)

“Within seconds after a person stopped under or near a tree, walkingsticks

dropped onto and crawled upon his body so that even to an experienced

entomologist it was an uncomfortable, creepy feeling.”

Oatman (1965)

REVIEW OF DIAPHEROMERA

Michigan Outbreak (1930s)

REVIEW OF DIAPHEROMERA

Michigan Outbreak (1930s)

REVIEW OF DIAPHEROMERA

REVIEW OF AUSTRALIAN SPECIES

DIDYMURIA VIOLESCENS

Above: Female, David Rentz

Right: Male, Paul Brock

Phasmida Species File

PODACANTHUS WILKINSONI

Right: Female, Kennedy HarrisBelow: Male (LT,PLT), ANIC (Paul Brock)Phasmida Species File

ANCHIALE AUSTROTESSELLATA

Male, NHM, Paul Brock

Phasmida Species File

REVIEW OF AUSTRALIAN SPECIES

Habitat, Paul Brock

Phasmida Species File

REVIEW OF AUSTRALIAN SPECIES

Campbell and Hadlington (1967)

Readshaw (1965) A Theory of Phasmatid Outbreak Release

Campbell (1974) Factors Limiting the Distribution and Abudance of the Three Species of Phasmatids (Phasmatodea: Phasmatidae) Which Occur in Plague Numbers in forests of South-Eastern Australia

Readshaw (1990) Phasmatid Outbreaks Revisiting

CLASSIC LITERATURE

Outbreaks are infrequent

Semi-voltine life cycle

Inability of predators and parasitoids to contain infestation

High fecundity

Slow migration

READSHAW’S CRITERIA

KENTROMORPHISM

Individuals reared at diff erent densities have diff erent colouration and morphology

Potentially analogous (homologous?) to density dependence in plaguing Orthoptera?

KENTROMORPHISM

http://davidavid.blogspot.co.uk/2006/11/just-phase.html

How general is this theory?

Take the model of Australian outbreaks

Apply it to other outbreaks

See what breaks

TESTING THE THEORY OF PHASMATID OUTBREAK RELEASE

Expanded by Campbell to be require an absence of forest catastrophe (mainly fi re) for a period of 10-80 years

No forest fi res associated with D. femorata outbreaks…

… but they always seem to occur in plantations or second growth forest

Conclusion:Outbreaks are linked to habitat disturbance, whether that be natural (forest fi re) or anthropogenic (plantations)

OUTBREAKS ARE INFREQUENT

Readshaw predicted this was important, as infestation levels only occur every other year, preventing a rapid escalation in predators/parasites

D. femorata is generally uni-voltine. Some Chinese pest species are up to tri-voltine.

Conclusion:May be important in specific in cases, but more generally phasmid outbreaks happen without this condition.

SEMI-VOLTINE LIFE CYCLE

Mymecomimesis semiglabra (Readshaw, 1965)

PREDATORS AND PARASITOIDS

Mymecomimesis semiglabra (Readshaw, 1965)

PREDATORS AND PARASITOIDS

Myna bird, introduced to Fiji to control Graeffea crouaniiGerald McCormack

PREDATORS AND PARASITOIDS

Exova tunana, parasitoid of Eurycantha insularisKimsey, Dewhurst & Nyaure (2013)

PREDATORS AND PARASITOIDS

If there is an infestation – the stick insects are not being predated or parasitised at a suffi cient rate to control the outbreak.

True by definition.

PREDATORS AND PARASITOIDS

All species involved lay many times more eggs than would be needed if no predators or parasitoids were present.

This is true for all Phasmid species.

Facilities outbreaks when population rise in phasmids is not immediately followed by a rise in predators and parasites.

Need to look at why this occurs. Given what else we know habitat disturbance is likely (forest fi res; altering of the forest ecosystem; movement of phasmids into plantations)

HIGH FECUNDITY

Diapheromera is wingless – movement confined to walking.

Gravid females of Australian species can glide – limited fl ight. Reports show that lighter males disperse more rapidly than females. Concentration of eggs beneath females.

Outbreaks generally occur in a very confined area, that spreads over several years and may merge with others to form widespread damage.

SLOW MIGRATION

Not known in any phasmids besides the Australian ones mentioned by Key.

The Australian species come from forest that is subject to natural forest fi res, this could be an evolutionary adaption to the eff ects of these.

KENTROMORPHISM

Disturbance of forest (either natural or anthropogenic)

Reduction in controlling species allows phasmid population to rise more rapidly than their predators

High fecundity and slow migration creates intense population rises on limited scales (at least initially)

Rejected ideas:Semi-voltine life cycle

Kentromorphism

GENERAL THEORY OF OUTBREAKS

GRAEFFEA CROUANII

CINHP, Gerald McCormack

GRAEFFEA CROUANII

Damage to coconut palm, Deesh, Swamy & Khan (2013)

GRAEFFEA CROUANII

Damage to coconut palm, Deesh, Swamy & Khan (2013)

BACULONISTRIA ALBA

Xiang Guowei in Hennemann et al (2008)Defoliation of Cupressus funebris