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Plant Focus

A guest post by Matt Candeias, host of the In Defense of Plants podcast and blog

PCR vs. Isolation and the War Against Oak Wilt

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Kevin Belter

Published May 2020 in International Oaks No. 31: 63–68


Bretziella fagacearum is a devastating disease. In no place in the United States are the losses of oaks in both quantity and diversity worse than in Central Texas. Current management strategies employed in Texas have not proven extremely effective. There is a desperate need to advance every tool possible that can assist those of us who dedicate our lives to the care of oaks. Recently, DNA analysis using polymerase chain reaction (PCR) was proven to out-compete traditional culture isolation as the best standard laboratory protocol in oak-wilt diagnostics (Yang and Juzwik 2017). Specifically, two PCR methods of testing for oak wilt have proven more consistent in finding the oak-wilt pathogen in various species within subgenus Quercus section Quercus1 as well as in section Lobatae (though in this section the results are equivocal). By extension, a reasonable expectation is that this method could more effectively diagnose oak wilt accurately from samples throughout the family Fagaceae. One of the unique and most useful aspects of this method is its ability to detect the fungus in wood samples that are as much as one year old. The fact is this fungus doesn’t stand a chance under the scrutiny of PCR.

1 For the updated infrageneric classification of the genus Quercus, see Denk et al. 2017.


Bretziella fagacearum, Ceratocystis fagacearum, polymerase chain reaction


Denk, T., G.W. Grimm, P.S. Manos, M. Deng, and A.L. Hipp. 2017. An updated infrageneric classification of the oaks: review of previous taxonomic schemes and synthesis of evolutionary patterns. In Oaks Physiological Ecology. Exploring the Functional Diversity of Genus Quercus L. Cham, Switzerland : Springer International Publishing AG. 

Luley, C.J., and C. Lytle. 2018. Landscape Diagnostics : DNA and RNA Testing for Landscape Pests. The Arboriculture Consultant 51(3) : 3-6.

Sternberg, G. 2009. Oak Wilt Rears Its Ugly Head. Oak News & Notes 13(2).

Sternberg, G. 2019. Managing Oak Wilt. International Oaks 30: 209-216.

Yang, A., and J. Juzwik. 2017. Use of Nested and Real-Time PCR for the Detection of Ceratocystis fagacearum in the Sapwood of Diseased Oak Species in Minnesota. Plant Disease 101(3): 480-486.