Forest Pathology
The following report describes three of the primary activities in the Forest Pathology Lab. The common theme of these activities is improving our understanding of the epidemiology of plant pathogens to make better disease management decisions.

Oak Wilt: The primary components of the project included an infectious forest disturbance (oak wilt, caused by Ceratocystis fagacearum), an indicator of forest health (the endangered avian species, the golden cheeked warbler), and their coexistence in a large tract of Central Texas savannah located within the Ft. Hood Military Installation, TX. The impact of oak wilt on the golden cheeked warbler (GCW) habitat utilizing remote sensing, a Geographic Information System (GIS) and geostatistical analyses is being analyzed. The spatial patterns of disease incidence are related to numerous independent variables using binary decision trees, semivariograms and kriging to create surface maps useful in predicting disease development. These studies will provide landowners and natural resource managers with better information on which to make disease management decisions.

Pierce’s Disease: The epidemiology of Pierce’s disease of grapes depends, in part, on vector behavior, inoculum sources, and the grape cultivars being infected. The colonization of different grape cultivars is being studied in containerized vines by inoculating them with different pathogen strains and assaying for the growth of the bacterium throughout the plants for a year following inoculation. Direct isolation, ELISA, and real time PCR are being used to study colonization and to compare the efficiency of each diagnostic technique. Sequential disease development within different vineyards is being surveyed to study the spread of the pathogen into, and within, vineyards. The spatial patterns of disease incidence and levels of disease severity are being analyzed.

Sudden Oak Death: The SOD pathogen apparently has been disseminated throughout the United States from contaminated nurseries in California during the past 2 years. The Forest Pathology Lab is involved in 3 different surveys within, and around, nurseries in Texas. One of the surveys involve those nurseries receiving plant materials from the contaminated CA nursery (trace forward survey) while the others include a sample of nurseries from throughout the state. Symptomatic plants from regulated host species are being processed the lab using direct isolation, ELISA and PCR to detect the pathogen.

1. Refereed Journal Articles

McBride, S., Appel, D.N., Pontasch, F.M., Gregg, L., and O.J. Alabi. 2017. Disease Notes: First report of tobacco ringspot virus infecting an American hybrid grape cultivar in Texas. Plant Disease 101:1062.

Montague, T., Hellman, E.W., Appel, D., and M. Krawitzky. 2015. Asexual propagation of grapevine transmits Pierce’s Disease pathogen (Xylella fastidiosa) to rooted cuttings. International Journal of Fruit Science 16: 135-149

Stewart, L.R., Morrison, M.L. Hutchinson, M.R., Appel, D.N., and R.N. Wilkins. 2014. Effect of a forest pathogen on habitat selection and quality for the endangered golden-cheeked warbler.  Wildlife Society Bulletin 38:279 – 287.

Stewart, L.R., Morrison, M.L., Appel, D.N., and R.N. Wilkins. 2014.  Spatial and temporal distribution of oak wilt in golden-cheeked warbler habitat.  Wildlife Society Bulletin 38:288-296.

 

1. Extension Publications

Appel, D., and A. Brown.  2017. Grapevine Trunk Diseases.  Texas A&M AgriLife Extension, EPLP-034.

McBride, S., and D.N. Appel. 2017.  Fire Blight of Ornamental Pears.  Texas A&M AgriLife Extension, EPLP-029.

McBride, S. and D.N. Appel. 2016.  Hypoxylon Canker of Oaks.  Texas A&M AgriLife Extension, EPLP-030.

McBride, S., and D.N. Appel. 2016. Rapid Decline of Post Oaks in Texas.  Texas A&M AgriLife Extension, EPLP-033.

Appel, D.N., Cameron, R.S., Wilson, A.D., and Johnson, J.D. 2014. How to identify and manage oak wilt in Texas. How-To-SR-1, U.S. Department of Agriculture, Forest Service, Southern Research Station, New Orleans, LA.

Appel, D.N. 2012. Pathogen biology and epidemiology, pages 22-24, in, J. Kamas, ed., Pierce’s Disease Overview and Management Guide: a resource for grape grower in Texas and other eastern U.S. growing areas. Texas AgriLife Extension Service. 103 pp.

Appel, D.N. 2012. Diagnosis of Pierces’s disease, pages 24-29, in, J. Kamas, ed., Pierce’s Disease Overview and Management Guide: a resource for grape grower in Texas and other eastern U.S. growing areas. Texas AgriLife Extension Service. 103 pp.

Appel, D.N., and J. Lewis. 2012. Further expansion of the pathogen into the Texas High Plains, pages 30 – 31, in, J. Kamas, ed., Pierce’s Disease Overview and Management Guide: a resource for grape grower in Texas and other eastern U.S. growing areas. Texas AgriLife Extension Service. 103 pp.

 

 

 

1. Books, Reviews and Book Chapters

Juzwik, J., and D. Appel.2016.  Oak Wilt. Pages 129 – 133, in, Bergdahl, A.D., and Hill, A., tech. cords. Diseases of trees in the Great Plains. Gen. Tech. Rep. RMRS-GTR-335. Fort Collins, CO. USDA Forest Service, Rocky Mountain Research Station. 229 pp.

McBride, S., and Appel, D. N. 2015.  Phymatotrichopsis Root Rot. In: “Compendium of Grape Diseases, Disorders, and Pests” Second Edition. W. F. Wilcox, W. D. Gubler, and J. K.    Uyemoto, eds., APS Press. St. Paul Minnesota.

 

1. Technical publications

McBride, S., Appel, D.N., Pontasch, F.M., Gregg, L., and O.J. Alabi. 2017. Survey for grapevine leafroll associated virus 3 in Texas vineyards. Phytopathology 107:1-2

Appel, D.N. and K. L. Ong.  2015.  The results of survey for citrus greening on the Upper Gulf
Coast of Texas.  Phytopathology 105 (Suppl. 2):S2.1.

McBride, S.A. and D. N. Appel. 2015. The control of cotton root rot in Texas winegrapes with the fungicide flutriafol.  Phytopathology 105 (Suppl. 2):S2.7.

Appel, D.N.  2014. Long term trends and epidemiology of Pierce’s Disease in Texas.  Page 86, in, Technical Abstracts of the 65^th ASEV National Conference, June 23-27, 2014, Austin, TX.

Kurdyla, T., Pham, J., McBride, S., and D.N. Appel. 2014. Survey and detection of Phytophthora ramorum, the Sudden Oak Death pathogen in Texas. Phytopathology 104:S2.6.

McBride, S., Appel, D., and K. Ong. 2014. A clinical perspective on public plant health trends in Texas. Phytopathology 104:S2.7.

McBride, S., Lewis, J.L. Kamas, J., and D.N. Appel.  2014. Promising strategies for managing cotton root rot of winegrapes in Texas. Page 165, in, Technical Abstracts of the 65^th ASEV National Conference, June 23-27, 2014, Austin, TX.

McBride, S., Lewis, J.L. Kamas, J., Black, M., and D.N. Appel. 2013. Field trials for control of Phymatotricopsis omnivore in grapevines in Texas. Phytopathology 103:7-7.

McBride, S., Richards, C., Appel, D., and J. Pase. 2012. Identification of a potential pyrophilous fungus following a forest fire in Bastrop, TX. Phytopathology 102:S4.78.

 

 

1. Popular Publications

Appel, D.N.  2015.  Bacterial leaf scorch on common woody plants of Texas landscapes.  TNLA
Green 17:7-9.