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Thomas Zitter

Thomas Zitter


319 Plant Science
(607) 255-7857

My research program focuses on the epidemiology and management of bacterial, fungal, and viral diseases of fresh market vegetable crops (esp. potatoes, cucurbits, and tomato) grown in upstate New York. I integrate my program by working cooperatively with scientists in other disciplines to evaluate chemical and biological agents, varietal resistance, and cultural disease management strategies for a number of vegetable crops. My work has relevancy for conventional and organic production of vegetable crops. For tomato we work cooperatively with a plant breeder to develop tomato varieties with multiple disease resistance by conventional breeding methods. For potatoes we study the use of sustainable and conventional products as seed piece, in-furrow or foliar application to minimize the lost of foliage and produce more blemish-free tubers. For cucurbits we evaluate products to minimize the effects of bacterial and fungal pathogens.

Research Focus

Following the characterization of the Alternaria species affecting potato (A. solani) and tomato (A. tomatophila) in terms of morphology and greenhouse pathogenicity, and demonstrating that two species of Alternaria are responsible for early blight of tomato and potato, we applied this information in the pursuit of improving the selection of disease resistant tomato lines and hybrids. Using the more pathogenic isolate of A. t. has been particularly important for selecting lines with the greatest level of disease resistance under conditions in the Northeast. Genetic resistance to early blight and late blight has been fixed in tomato lines in cooperation with plant breeders, and these lines have been field tested to select for superior performance of earliness and yield potential in two locations in NY. NC06115, a jointly developed hybrid from Cornell and NCSU, performed exceptionally well in inoculated field plots in 2008. When teamed up with reduced-risk fungicides with lower environmental impact quotients (EIQ), it was possible to reduce seasonal EIQ values from 303 for the standard weekly spray with chlorothalonil to just 49 using a number of fungicides with low EIQs; this resulted in even better disease control than the standard chlorothalonil program. In 2009 we plan to repeat this study but with emphasis on reducing the number of sprays required with the same reduce-risk fungicides. A screen program was initiated to confirm resistance to Septoria leaf spot in some existing germplasm previously used for Septoria leaf spot (SLS) resistance. From this screening, two lines were selected for crossing with the LB/EB line mentioned above to generate F2 populations, and subsequent screening showed that SLS is probably controlled by a single gene, and that resistance is partially but not fully dominant under field conditions. In 2009 we plan to test lines that may be potentially fixed for triple genetic resistance with reduce-risk fungicides and a reduce spray program following the TOM-CAST program. In potato we are working with a horticulturist to reduce the damaging effects of silver scurf, black scurf, black dot by integrating seed and in-furrow treatments with foliar applications, and postharvest treatments. We are also investigating the use of in-furrow applications of a nematicide (oxamyl) and its affect on reducing early dying in potato. We had some excellent results in 2008 and growers are anxious to have use repeat this work in 2009. We will expand this work to see if we can continue to reduce the degree of potato early dying, determine if Verticillium is important in the state, and determine the role of black dot in this complex disease response. We continue to evaluate existing and new potato cultivars for their reaction to several diseases including pink rot. For cucurbits we studied the epidemiology of bacterial diseases of cucurbits and verified methods to reduce the spread of bacteria via seed by evaluating several seed treatments. We continue to follow the control of powdery mildew in cucurbits in the face of continued loss of fungicides due to fungal resistance. We participate in an interregional grant to monitor the occurrence and spread of downy mildew of cucurbits.

Outreach and Extension Focus

My extension program reaches out to other colleagues (Horticulture, Plant Breeding), growers, IPM specialists, professional scouts, Industry representatives and many other stakeholders through my internationally recognized vegetable disease web site. My program consists of developing disease management strategies for tomato, potato and cucurbits that are both economically and environmentally sound for fresh market vegetable production. We develop and encourage the use of disease resistant varieties when possible. We hope that some of integrated programs will result in practices adaptable for organic production. I serve as section editor for the Disease Section of the Pest Management Guidelines for Commercial Vegetable and Potato Production, provide Newsletter articles for CCE Field Staff including fungicide news updates, and provide Disease Diagnostic tools as part of the Vegetable MD web site. During 2008 the web site received over 2.3 million hits. I have made available countless number of disease images for use in agent/grower education via the web. I serve as editor of two important books, Compendium of Tomato Diseases and Compendium of Cucurbit Diseases that are wide used by crop specialists. I also extend the latest information on Plant Disease control at numerous meetings held around the state. I participate in IPM twilight meetings in 3-4 counties during the summer months to provide hands on experience to my clientele. I am a frequent speaker at vegetable conferences throughout the northeast.

Awards and Honors

  • Recognition of 40th anniversary of Conference creation (2012) Internation Pepper Conference

Presentations and Activities

  • Development and Use of Cultivars with Resistance or Tolerances to Late Blight, Early Blight and Septoria Leaf Spot. 2013 Vegetable EXPO. January 2013. Syracuse, NY.