Protecting Tree Health in Texas Communities and Woodlands
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abstract
Our valuable natural forests and urban trees are under a barrage of emerging and introduced tree pathogens. This is particularly true in Texas where the enormous value of these resources are subject to extremely stressful climates and a continual invasion of exotictree pathogens acrosslengthy borders. Solutions to the diseases areas complex as the pathogens themselves, the tree hosts they infect and the diseases they cause. There is relatively little research currently being conducted to provide practical, effective options for directly managing tree pathogens and mitigating thier impacts. This is particularly obvious when interacting with clientele expecting some useful response from AgriLife Extension when they reach out for solutions to their tree problems in Texas. Improvements in early detection and diagnostics would be very helpful, because these issues are the first line ofdefense against any plant pathogen. For improving plant disease diagnosis, studies to develop a RT-PCR protocol for detecting the oak wilt pathogen, Bretziella fagacearum will be conducted in this proposed M-S project. There are several limitations to the most common method for diagnosing a tree suspected of being infected with oak wilt. This method relies on growing the fungus out of the sample in the laboratory, and can take weeks to complete and may have unacceptably high levels of false negative results (the tree may be infected but the sample does not contain the fungus). An RT-PCR method will be quicker and far more sensitive than isolating the pathogen, but requires a great deal of effort to verify the reliability and consistency of the test. Another potential advantage would the ability to successfully conduct a post mortum on diseased trees to diagnose a case of oak wilt after it the tree has died.The other issue, concerning the monitioring of exotic pathogens, will also be a focus of the proposed project There will be surveys for Citrus Greening, caused by a bacterium called Candidatus liberabacter asiaticus, and Sudden Oak Death, caused by the fungus Phytophthora ramorum. These two pathogens pose an immediate and significant threat to tthe Texas citrus industry as well as the considerable oak resources of the State. Another important issue that will be addressed is the need for improvements to methods ofdirect control and saving trees at threat of infection by the oak wilt pathogen. Tree injection with a fungicide has proven to be an effective option in the management of oak wilt. One technique, called the macro-injection method, has dominated the injection market for the past 20 years because there were reliable research results to support its use. More recently, there has been a proliferation of new methods for injecting trees, mostly based on "micro" injection methods. These new methods are purportedly faster, less laborius, and better for the tree than macroinjection. However, the only evidence to support these claims is in need of further verification and testing. That is another objective of this project, to test methods of injecting trees with both systems under conditions of natural infection by the pathogen to determine whether the advantages and disadvantages to how trees are currently being injected. The information generated by the proposed studies will be of great interest to a wide variety of clientele in both the public and private sectors. One of the greatest impacts will be on the Central Texas urban forests where there is a thriving, well - trained and organized arborilogical industry in Texas ready to adopt better technology for dealing with oak wilt. The PI regularly meets with arborists and homeowners at 25 - 30 meetings annually, including several Master Gardener trainings in Texas counties. Factsheets will be published through the Texas A&M AgriLIfe Bookstore for distribution on the internet, and there will publications in peer-reveiwed journals for the braoder scientific community.
