Geosmithia pallida (G. Sm.) M. Kolarík, Kubátová & Paotová

California Pest Rating for
Geosmithia pallida (G. Sm.) M. Kolarík, Kubátová & Paotová
 Pest Rating:  C


Initiating Event:

During August 2014, The CDFA Pathology Laboratory received official samples of diseased oak trees exhibiting symptoms of foaming cankers, collected from residential and commercial landscape sites in Marin and Napa counties.  The fungal pathogen Geosmithia pallida, causing foamy bark canker disease, was identified by Suzanne Latham, CDFA Plant Pathologist.  Within a few weeks of this detection, G. pallida was also detected in official oak samples collected in Santa Clara and El Dorado counties.  Prior to these official reports, the foamy bark canker disease has been known to exist throughout southern California extending to Monterey County.   The pathogen has not been previously rated and therefore, the need for a definite rating is necessitated and proposed.

History & Status:

Background:  Researchers at the Department of Plant Pathology, University of California, Riverside, have observed since 2012 decline of coast live oak (Quercus agrifolia) throughout urban landscapes in southern California (Lynch, et al., 2014). The fungus Geosmithia pallida was determined to be the cause of the observed symptoms which were successfully reproduced in pathogenicity tests on detached coast live oak shoots and in 2014, Lynch et al. provided the first report of G. pallida causing foamy bark canker on coast live oak in California and the USA.  They recovered the fungal species from symptomatic plant tissues associated with the western oak bark beetle Pseudopityophthorus pubipennis.  The western oak bark beetle is native to California and common as a secondary agent that readily attacks stressed plants.  It has not been previously associated with disease; however, cryptic species may be common among bark and ambrosia beetles (Lynch et al., 2014). The beetle burrows through the tree bark forming shallow tunnels below the bark and across the grain of the wood.  Eggs are laid within the tunnels and on hatching, the developing larvae form tunnels at right angles to their main tunnel and mostly within the inner bark or phloem close to the surface.  The fungus is dry-spored and occurs in the tunnels or galleries built by the beetles. Once insect larvae develop, they carry fungal spores and fly to other uninfected trees thereby spreading the fungus.

The fungal pathogen was originally placed in the genus Penicillium as the species, P. palladium which was later considered a synonym of Geosmithia putterillii (Pitt, 1979).  The latter species is a complex group of species comprising three genetically isolated cryptic species with worldwide distribution (Kolařík et al., 2004). Several isolates have been acquired from wood or subcorticolous insects.  In 2004, based on molecular and morphological analyses, Kolařík and others separated G. pallida from the G. putterillii species complex.

Hosts: Quercus agrifolia (coast live oak), Q. rubra (northern red oak), Q. wislizenii (interior live oak).

Symptoms:  Symptoms of G. pallida infection occur on the trunk and primary branches of trees and include wet discoloration seeping through entry holes caused by the western oak bark beetle.  Necrotic phloem and xylem tissue is apparent beneath the outer bark.  Multiple beetle entry holes may also be apparent on a single tree.  As the disease advances, a cream to reddish sap may ooze from the entry hole, followed by a prolific foamy liquid which may run down the trunk for about 2 feet.  The symptoms may be confused with those caused by Fusarium dieback/Polyphagous Shot Hole Borer; however, the size of the entry hole associated with foamy canker is smaller than those made by the Polyphagous Shot Hole Borer (Lynch et al., 2014).  In Europe, in laboratory plant growth culture tests using garden cress plants, G. pallida inhibited root growth by 25% whereas stem growth was almost unimpaired (Čižková et al., 2005).

Damage Potential:  Symptom associated with foamy bark canker disease on coast live oak result in branch dieback and tree death.

Transmission:  The fungal pathogen is associated with the western oak bark beetle and transmitted from infected to non-infected trees during movement and feeding by the beetle.  The fungus is also spread to uninfected sites through the movement of infected wood, such as firewood, and contaminated pruning and cutting equipment.

Worldwide Distribution Geosmithia pallida has a worldwide distribution (Kolařík et al., 2004).

Official Control There are no reports of official control of the fungal pathogen.

California Distribution: Los Angeles, Orange, Riverside, Santa Barbara, Ventura and Monterey counties (Lynch et al., 2014).  CDFA official samples collected from El Dorado, Napa, Marin and Santa Clara counties were positive for Geosmithia pallida (see ‘Initiating Event’).

California Interceptions:  Geosmithia pallida has not been intercepted in imported official shipments to California.

The risk Geosmithia pallida would pose to California is evaluated below.

Consequences of Introduction: 

 1) Climate/Host Interaction: Evaluate if the pest would have suitable hosts and climate to establish in California. Score:

– Low (1) Not likely to establish in California; or likely to establish in very limited areas.

– Medium (2) may be able to establish in a larger but limited part of California.

– High (3) likely to establish a widespread distribution in California.

Risk is High (3). Geosmithia pallida is already established in ten counties.

2) Known Pest Host Range: Evaluate the host range of the pest. Score:

– Low (1) has a very limited host range.

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

Risk is Low (1).   Presently the pathogen has been observed causing decline and death of coast live oak in association with the western oak bark beetle.  In California, coast live oak occurs in the coastal ranges from north central to southern counties. So, even though Geosmithia pallida has been found affecting one host, the latter as well as other host species of oak are relatively wide spread throughout the State.

 3) Pest Dispersal Potential: Evaluate the natural and artificial dispersal potential of the pest. Score:

– Low (1) does not have high reproductive or dispersal potential.

– Medium (2) has either high reproductive or dispersal potential.

– High (3) has both high reproduction and dispersal potential.

Risk is High (3).  The fungal pathogen is artificially spread by movement of its associated insect vector and infected wood. The western oak bark beetle vector is native to California and is capable of moving and finding habitation throughout the State.

4) Economic Impact: Evaluate the economic impact of the pest to California using the criteria below. Score:

A.  The pest could lower crop yield.

B.  The pest could lower crop value (includes increasing crop production costs).

C.  The pest could trigger the loss of markets (includes quarantines).

D.  The pest could negatively change normal cultural practices.

E.  The pest can vector, or is vectored, by another pestiferous organism.

F.  The organism is injurious or poisonous to agriculturally important animals.

G.  The organism can interfere with the delivery or supply of water for agricultural uses.

– Low (1) causes 0 or 1 of these impacts.

– Medium (2) causes 2 of these impacts.

– High (3) causes 3 or more of these impacts.

Risk is High (3).  Foamy bark canker disease caused by Geosmithia pallida could result in tree decline and death of coast live oak trees.  Currently, there are no known control measures against this pathogen. Early detection is noted as being crucial and could lead to pruning back infected branches, and other cultural treatments.  Regulations against movement of oak firewood could be necessary and this could directly trigger loss of markets. Plus the pathogen is easily vectored by the native western oak bark beetle.   

5) Environmental Impact: Evaluate the environmental impact of the pest on California using the criteria below.

A.  The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.

B.  The pest could directly affect threatened or endangered species.

C.  The pest could impact threatened or endangered species by disrupting critical habitats.

D.  The pest could trigger additional official or private treatment programs.

E.  The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Score the pest for Environmental Impact. Score:

– Low (1) causes none of the above to occur.

– Medium (2) causes one of the above to occur.

– High (3) causes two or more of the above to occur.

 Risk is High (3).  The decline of infected oak trees could have significant environmental impact by disrupting natural communities, critical habitats or changing the ecosystem process. The potential loss of coast live oak could seriously threaten the conservation of the host plant thereby negatively impacting the 2001 California Oak Woodlands Conservation Act approved by California State Legislature.

Consequences of Introduction to California for Geosmithia pallida:

Add up the total score and include it here. (Score)

-Low = 5-8 points

-Medium = 9-12 points

-High = 13-15 points

Total points obtained on evaluation of consequences of introduction of Geosmithia pallida to California = (13).

6) Post Entry Distribution and Survey Information: Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included. (Score)

-Not established (0) Pest never detected in California, or known only from incursions.

-Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).

-Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.

-High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Evaluation is High (-3). The pathogen has been reported in more than two contiguous or non-contiguous counties with suitable host and climate.

Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: (Score)

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 10.


The pathogen is capable of spreading throughout California wherever suitable host and climate are present.  Since its detection in the southern counties it has spread to the central coastal region.  With the widespread distribution of the host plant and the associated western oak bark beetle vector, there is the possibility for the foamy bark canker disease to continue to spread statewide.  Further statewide survey and reports would be necessary to confirm this probability.  With further spread of the pathogen, the numeric score assessed here is not expected to change by much, thereby, strengthening its proposed ‘C’ rating.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for the Foamy Bark Canker Disease pathogen, Geosmithia pallida is C.


Čížková, D., P. Šrůtka, M. Kolařík, A. Kubátová and S. Pažoutová.  2005.  Assessing the pathogenic effect of Fusarium, Geosmithia and Ophiostoma fungi from broad-leaved trees.  Folia Microbiologica, 50:59-62.

Kolařík, M., A. Kubátová, S. Pažoutová and Petr Šrůtka.  2004.  Morphological and molecular characterization of Geosmithia putterillii, G. pallida comb. nov. and G. flava sp. nov., associated with subcorticolous insects.  Mycological Research 108: 1053-1069.

Lynch, S. C., D. H. Wang, J. S. Mayorquin, P. Rugman-Jones, R. Southamer and A. Eskalen.  2004.  First report of Geosmithia pallida causing foamy bark canker, a new disease on coast live oak (Quercus agrifolia) in association with Pseudopityophthorus pubipenis (western oak bark beetle, Coleoptera: Curculionidae: Scolytinae) in California.  Plant Disease “First Look” paper posted 05/21/2014:

Lynch, S. P., R. Rugman-Jones, R. Southamer and A. Eskalen.  (Not dated).  Pest Alert:  Geosmithia pallida and Western Oak Bark Beetle (Pseudopityophthorus pubipenis) causing foamy bark canker disease on coast live oak (Quercus agrifolia) in California.  University of California, Riverside.

Pitt, J. I. (1979) Geosmithia gen. nov. for Penicillium lavendulum and related species. Canadian Journal of Botany 57: 2021–2030.

Responsible Party:

John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: 916-262-1110,[@]

Comment Period:

The 45-day comment period opened on Wednesday, October 28, 2015 and closed on December 12, 2015.

 Pest Rating:  C

Posted by ls