Keith S. Yoder

Professor

Education

Ph.D., Plant Pathology, Michigan State University, 1974

M.S., Plant Pathology, Michigan State University, 1972

B.A., Biology, Goshen College, 1968

Experience

  • March 2000 – present: Professor, Department of Plant Pathology, Physiology & Weed Science, Virginia Tech, Virginia Polytechnic Institute and State University, Blacksburg, and Virginia Tech Agricultural Research and Extension Center, Winchester.
  • March 1982 – March 2000: Associate Professor, Department of Plant Pathology, Physiology & Weed Science, Virginia Polytechnic Institute and State University, Blacksburg, and Virginia Tech Agricultural Research and Extension Center, Winchester.
  • Nov. 1976 – March 1982: Assistant Professor, Department of Plant Pathology, Physiology & Weed Science, Virginia Polytechnic Institute and State University, Blacksburg and Winchester Fruit Research Laboratory.
  • July 1974 – Nov. 1976: Research Plant Pathologist, E. I. DuPont de Nemours and Co., Wilmington, DE
  • Sept. 1971 – July 1974: Graduate Research Assistant, Department of Botany and Plant Pathology, Michigan State University, East Lansing
  • Jan. 1969 – Sept. 1971: Research Technician, Department of Botany and Plant Pathology, Michigan State University, East Lansing

Program Focus

My long-term responsibilities and professional objectives:

  1. Lend my scientific expertise in an advisory capacity to production agriculture.
  2. Focusing on maintaining an ongoing program for practical, economical, and environmentally sound management of diseases in tree fruits.
  3. Specialize in fungicide activity spectrum, fungicide resistance management, apple cultivar resistance and susceptibility.
    With a 60/40% mix of research/extension in tree fruits pathology, ongoing research focuses on alternative tree fruit disease management strategies, fungicide activity spectrum and fungicide resistance management. Current research is directed toward disease susceptibility and horticultural acceptability of scab-resistant apple cultivars, disease inoculum reduction, etc.

Current Research

  • Management of Diseases of Tree Fruits
    Impact: High levels of fungicide resistance in apple scab populations indicate that replacement programs must be adopted. The potential for resistance by several important diseases to several fungicide classes, the need for economic management of ten or more diseases, and varying disease pressure from year to year across fruit-growing regions of Virginia underscore the need for ongoing testing of new materials and novel approaches for economical, environmentally sensitive tree fruit disease management. Ongoing fungicide evaluations are essential to tree fruit disease management in view of the development of resistance to current materials and potential loss of older, useful materials through withdrawal of registration. A long-term goal of the resistance monitoring research is to direct it toward DNA-based methodologies so that we can rapidly screen for resistance and more quickly employ the appropriate disease management strategies.
  • Fire Blight
    Fire blight is a bacterial disease (caused by Erwinia amylovora) that attacks apples, pears and several rosaceous ornamental species. It is a major ongoing concern in apple production because of the serious threat to susceptible apple rootstocks (M.9, M.26 and Mark) and cultivars now being planted, including Gala, Fuji, York, Idared, Pink Lady and Rome Beauty. Typically the bacteria overwinter in cankers and initial infection occurs during warm, wet weather at bloom. Hail or violent storms frequently trigger secondary infection of late bloom and shoots in late spring and early summer. A 100-acre orchard in Virginia lost more than 2,400 Red Delicious/M.26-rooted trees to fire blight following a single blossom infection event in 1991.
  • Multistate Project NC-140
    Multistate Project NC-140 is involved with improving economic and environmental sustainability in tree-fruit production through changes in rootstock use. The NC-140 project has five objectives, one of which is to better understand the impacts of biotic and abiotic stresses on scion/rootstock combinations in temperate-zone fruit trees. Under this objective, we will be testing apple rootstocks for susceptibility/resistance to Tomato Ring Spot Virus (TmRSV), causal agent of Apple Union Necrosis and Decline (AUND).

Program Focus

Long-term professional extension objectives:

  • Lend my scientific expertise in an advisory capacity to production agriculture.
  • Focusing on maintaining an ongoing program for practical, economical, and environmentally sound management of diseases in tree fruits.
  • Specialize in fungicide activity spectrum, fungicide resistance management, apple cultivar disease resistance and susceptibility.
    Cooperative extension and outreach responsibilities and activities include providing economical and environmentally sound tree fruit disease management recommendations to growers and fruit crop production advisors in Virginia and the mid-Atlantic region and advising growers of changes in fruit pesticide regulations that affect their operations. We post have a web site with updates information on Winchester area diseases.
  • Yoder K., G. Peck, L. Combs, R. Byers. 2013. Using a pollen tube growth model to improve bloom thinning for organic production. Acta Horticulturae—Sustainability Through Integrated and Organic Horticulture. (ISHS) 1001:207-214.
  • Marine, S. C. D. G. Schmale III, and K. S. Yoder. 2012. First report of reduced sensitivity to a QoI fungicide in apple scab (Venturia inaequalis) in Virginia and Maryland. Plant Disease 96:1376. Link to publication.
  • Gleason M., J. Batzer, G. Sun, R. Zhang, M. Díaz Arias, T. Sutton, P. Crous, M. Ivanovic, P. McManus, D. Cooley, U. Mayr, R. Weber, K. Yoder, E. Del Ponte, A. Biggs, B. Oertel. 2011. A new view of sooty blotch and flyspeck. Plant Disease 95: 368-383. Link to publication.
  • Miller S., K. Yoder. 2011. Chemical and Cultural Approaches to Enhancing Host Resistance to Fire Blight: Plant Growth Regulators. Pp. 249-255 in Fire Blight; History, Biology and Management. T. van der Zwet, N. Orolaza-Halbrendt and W. Zeller eds. APS Press. St. Paul MN. 421 pp.
  • Biggs, A. R., G. W. Sundin, D. A. Rosenberger, K. S. Yoder, and T. B. Sutton, 2010. Relative susceptibility of selected apple cultivars to apple scab caused by Venturia inaequalis. Plant Health Progress. Link to publication.
  • Biggs, A. R., D. R. Cooley, D. A. Rosenberger, and K. S. Yoder. 2010. Relative susceptibility of selected apple cultivars to sooty blotch and flyspeck. Plant Health Progress. Link to publication.
  • Marine, S. C., K. S. Yoder, and A. Baudoin. 2010. Powdery mildew of apple. The Plant Health Instructor. Link to publication.
  • Diaz Arias, M. M., J. C. Batzer, T. C. Harrington, A. W. Wong, S. C. Bost, D. R. Cooley, M. A. Ellis, J. R. Hartman, D. A. Rosenberger, G. W. Sundin, T. B. Sutton, J. W. Travis, M. J. Wheeler, K. S., Yoder, and M. L. Gleason. 2010. Diversity and biogeography of sooty blotch and flyspeck fungi on apple in the eastern and midwestern United States. Phytopathology 100:345-355. Link to publication.
  • Yoder, K., L. Combs, and R. Yuan. 2010. Effect of temperature on apple pollen tube growth: implications for bloom thinning. Proceedings of the 105th Annual Meeting of the Washington State Horticultural Association, pp. 68-78.
  • Biggs, A. R., Rosenberger, D. A., Yoder, K. S., Kiyomoto, R. K., Cooley, D. R., and Sutton, T. B. 2009. Relative susceptibility of selected apple cultivars to cedar apple rust and quince rust. Plant Health Progress. Link to publication.
  • Biggs, A. R., Yoder, K. S., and Rosenberger, D. A. 2009. Relative susceptibility of selected apple cultivars to powdery mildew caused by Podosphaera leucotricha. Plant Health Progress. Link to publication.
  • Sundin, G. W. N. A. Werner, K. S. Yoder, and H. S. Aldwinckle, 2009. Field Evaluation of Biological Control of Fire Blight in the Eastern United States. Plant Dis. 93:386-394. Link to publication.
  • Yoder, K., R. Yuan, L. Combs, R. Byers, J. McFerson and T. Schmidt. 2009. Effects of temperature and the combination of liquid lime sulfur and fish oil on pollen germination, pollen tube growth, and fruit set in apples. HortScience 44(5):1277-1283. Link to publication.
  • Janisiewicz, W.J, R.A Saftner, W.S. Conway K.S. Yoder. 2008. Control of blue mold decay of apple during commercial controlled atmosphere storage with yeast antagonists and sodium bicarbonate. Postharvest Biology and Technology 49:374–378.
  • Marine, S.C., D.G Schmale III, and K.S. Yoder. 2007. Resistance to myclobutanil in populations of Venturia inaequalis in Winchester, Virginia. Plant Health Progress DOI:10.1094/PHP-2007-1113-01-RS. Link to publication.