Geosmithia Species in Florida: Common Fungal Symbionts of Wood-Boring Bark Beetles
A photo of a colony of Geosmithia morbida fungus in a petri dish.
view on EDIS



How to Cite

Huang, Yin-Tse, and Jiri Hulcr. 2019. “Geosmithia Species in Florida: Common Fungal Symbionts of Wood-Boring Bark Beetles: FR-343/FR412, 1/2019”. EDIS 2019 (1). Gainesville, FL.


Geosmithia are fungi associated with wood-boring bark beetles. Most Geosmithia species do no harm to host trees, but the canker-causing Geosmithia morbida and its beetle vector, the walnut twig beetle, cause the disease complex known as thousand cankers disease on walnut trees. Continuous surveys in Florida have found neither Geosmithia morbida nor its beetle vector in the state, but many native Geosmithia species have been recovered. These native species look similar to the pathogenic fungus but are harmless to their plant hosts. This 4-page fact sheet written by Yin-Tse Huang and Jiri Hulcr and published by the UF/IFAS School of Forest Resources and Conservation provides basic guidelines to sample Geosmithia species in the field and information for distinguishing the plant pathogenic Geosmithia morbida from other Geosmithia species.
view on EDIS


Hishinuma, S. 2017. Interactions among the Walnut Twig Beetle, Pityophthorus Juglandis, the pathogenic fungus, Geosmithia Morbida, and host species in thousand cankers disease in California (Ph.D. thesis). University of California, Davis, United States.

Hishinuma, S. M., P. L. Dallara, M. A. Yaghmour, M. M. Zerillo, C. M. Parker, T. V. Roubtsova, T. L. Nguyen, N. A. Tisserat, R. M. Bostock, M. L. Flint., and S. J. Seybold. 2016. "Wingnut (Juglandaceae) as a new generic host for Pityophthorus juglandis (Coleoptera: Curculionidae) and the thousand cankers disease pathogen, Geosmithia morbida (Ascomycota: Hypocreales)." Can. Entomol. 148, 83-91. doi:10.4039/tce.2015.37

Hulcr, J., and L. L. Stelinski. 2017. "The ambrosia symbiosis: From evolutionary ecology to practical management." Annu. Rev. Entomol. 62, 285-303. doi:10.1146/annurev-ento-031616-035105

Jankowiak, R., M. Kolařík, and P. Bilański. 2014. "Association of Geosmithia fungi (Ascomycota: Hypocreales) with pine- and spruce-infesting bark beetles in Poland." Fungal Ecol. 11, 71-79. doi:10.1016/j.funeco.2014.04.002

Juzwik, J., M. T. Banik, S. E. Reed, J. T. English, and M. D. Ginzel. 2015. "Geosmithia morbida found on weevil species Stenominus pallidus in Indiana." Plant Health Prog. 16, 7-10.

Juzwik, J., M. McDermott-Kubeczko, T. J. Stewart, and M. D. Ginzel. 2016. "First report of Geosmithia morbida on ambrosia beetles emerged from Thousand Cankers-diseased Juglans nigra in Ohio." Plant Dis. 100, 1238-1238. doi:10.1094/PDIS-10-15-1155-PDN

Kolařík, M., E. Freeland, C. Utley, and N. Tisserat. 2011. "Geosmithia morbida sp. nov., a new phytopathogenic species living in symbiosis with the walnut twig beetle (Pityophthorus juglandis) on Juglans in USA." Mycologia 103, 325-332. doi:10.3852/10-124

Kolařík, M., J. Hulcr, N. Tisserat, W. D. Beer, M. Kostovčík, Z. Kolaříková, S. J. Seybold, and D. M. Rizzo. 2017. "Geosmithia associated with bark beetles and woodborers in the western USA: taxonomic diversity and vector specificity." Mycologia 109, 185-199. doi:10.1080/00275514.2017.1303861

Kolařík, M., and R. Jankowiak. 2013. "Vector affinity and diversity of Geosmithia fungi living on subcortical insects inhabiting pinaceae species in central and northeastern Europe." Microb. Ecol. 66, 682-700. doi:10.1007/s00248-013-0228-x

Kolařík, M., and L. R. Kirkendall. 2010. "Evidence for a new lineage of primary ambrosia fungi in Geosmithia Pitt (Ascomycota: Hypocreales)." Fungal Biol. 114, 676-689. doi:10.1016/j.funbio.2010.06.005

Kolařík, M., A. Kubátová, S. Pažoutová, and P. Šrûtka. 2004. "Morphological and molecular characterisation of Geosmithia putterillii, G. pallida comb. nov. and G. flava sp. nov., associated with subcorticolous insects." Mycol. Res. 108, 1053-1069. doi:10.1017/S0953756204000796

Pitt, J. I. 1979. "Geosmithia gen. nov. for Penicillium lavendulum and related species." Can. J. Bot. 57, 2021-2030. doi:10.1139/b79-252

Tisserat, N., W. Cranshaw, D. Leatherman, C. Utley, and K. Alexander. 2009. "Black walnut mortality in Colorado caused by the walnut twig beetle and thousand cankers disease." Plant Health Prog. doi:10.1094/PHP-2009-0811-01-RS

Tisserat, N., W. Cranshaw, M. L. Putnam, J. Pscheidt, C. A. Leslie, M. Murray, J. Hoffman, Y. Barkley, K. Alexander, and S. J. Seybold. 2011. "Thousand cankers disease is widespread on black walnut, Juglans nigra, in the western United States." Plant Health Progress. doi:10.1094/PHP-2011-0630-01-BR. Available:

United States Department of Agriculture Animal and Plant Health Inspection Service. Thousand Cankers Disease (website). 2018. Available at: (accessed 9.15.2018).

United States Department of Agriculture Forest Service, the Purdue University Department of Forestry and Natural Resources et al. Thousand Cankers Disease (website). 2014. Available at: (accessed 6.25.18).

Utley, C., T. Nguyen, T. Roubtsova, M. Coggeshall, T. M. Ford, L. J. Grauke, A. D. Graves, C. A. Leslie, J. McKenna, K. Woeste, M. A. Yaghmour, S. J. Seybold, R. M. Bostock, and N. Tisserat. 2012. "Susceptibility of Walnut and Hickory Species to Geosmithia morbida." Plant Dis. 97, 601-607. doi:10.1094/PDIS-07-12-0636-RE

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International (CC BY-NC-ND 4.0) license.