Kari A. Peter, Ph.D.

Assistant Professor, Tree Fruit Pathology


    Apple and pear diseases
    Peach, cherry, other stone fruit diseases
    Tree fruit disease management



    About Me

    Areas of interest

    Diseases of stone and pome fruit, especially bacterial diseases and postharvest apple rots; educational programming for integrated management for pre- and postharvest tree fruit diseases and fungicide resistance

    The Tree Fruit Pathology Program at Penn State

    Growing tree fruit is a huge industry in the Mid-Atlantic region, with Pennsylvania the fourth largest producer of apples in the United States. The Tree Fruit Pathology Program at Penn State serves tree fruit growers in Pennsylvania and Maryland through the Mid-Atlantic Fruit Consortium, a collaboration enabling Penn State University, the University of Maryland, and West Virginia University to share resources and expertise.

    My Extension Program focuses on educating growers about effective, sustainable disease management strategies for important diseases problematic in the region. This includes regular participation in winter and spring/summer meetings and timely articles and disease updates in the online periodical Fruit Times. In addition, since we're located in the heart of the apple country, we regularly answer questions from "walk-ins", phone calls, and emails from growers, crop consultants, Extension educators, journalists, and anyone with a burning question about tree fruit diseases.

    My philosophy for addressing Pennsylvania's and Maryland's tree fruit industry research needs is to follow a holistic approach: all pest management systems (organic to conventional) and full circle (pre- and postharvest diseases). My research program includes developing better management strategies for controlling bacterial diseases, specifically fire blight and bacterial spot, and apple fruit rot diseases occurring during storage; identifying possible emerging pre- and postharvest apple fruit rots; and developing tools to quickly identify fungicide resistance for problematic fungal diseases so to assist growers with disease management decisions within season. In addition, I work closely with several companies evaluating chemistries and products for suitability in controlling tree fruit diseases in Pennsylvania and Maryland.


    Ramos, L. S., Sinn, J., Lehman, B. L., Pfeufer, E., Peter, K. A., and McNellis, T. W. 2015. An Erwinia amylovora pyrC mutant is auxotrophic for pyrimidine yet causes fire blight in apple tree shoots and grows in immature pear and apple fruit tissue. Letters in Applied Microbiology. 60 (6): 572 - 579.

    Peter, K. A., Gaskins V. L., Lehman, B., and Jurick II, W. M. 2015. First Report of Brown Rot on Apple Fruit Caused by Monilinia fructicola in Pennsylvania Plant Disease. 99 (8): 1179.

    Ramos, L. S., Lehman, B. L., Peter, K. A., and McNellis, T. W. 2014. Mutation of the Erwinia amylovora argD gene causes arginine auxotrophy, nonpathogenicity in apples, and reduced virulence in pears. Applied and Environmental Microbiology. 80 (21): 6739 - 6749.

    Vico, I., Gaskins, V., Duduk, N., Vasić, M., Yu, J., Peter, K.A., and Jurick II, W. M. 2014. First report of Penicillium crustosum causing blue mold on stored apple fruit in Serbia. Plant Disease. 98 (10): 1430.

    Janisiewicz, W. J., Jurick II, W .M., Peter, K. A., Kurtzman, C. P., and Buyer, J. S. 2014. Yeasts associated with plums and their potential for controlling brown rot after harvest. Yeast. 31 (6): 207 – 218.

    Jurick II, W. M., Vico, I., Gaskins, V. L., Janisiewicz, W. J., and Peter, K. A. 2013. Initial description of Neofusicoccum ribis causing postharvest decay of apple fruit from cold storage in Pennsylvania. Plant Disease. 97 (7): 999.

    Jurick II, W. M., Vico, I., Gaskins, V. L., Janisiewicz, W. J., and Peter, K. A. 2013. First report of Botryosphaeria dothidea causing white rot on apple fruit in Maryland. Plant Disease. 97 (7): 999.

    Janisiewicz, W. J., Jurick II, W .M., Vico, I., Peter, K. A., Buyer, J. S. 2013. Culturable bacteria of plums and their potential for control of brown rot after harvest. Postharvest Biology and Technology. 76: 145 - 151.

    Peter, K. A., Vico, I., Gaskins V. L., Janisiewicz, W. J., Saftner, R. A., and Jurick II, W. M. 2012. First report of Penicillium carneum causing blue mold on stored apples in Pennsylvania. Plant Disease. 96 (12): 1823.

    Cilia, M.*, Peter, K. A.*, Bereman, M. S.*, Howe, K., Fish, T., Smith, D., Gildow, F., MacCoss, M. J., Thannhauser, T. and Gray, S. M. 2012. Host proteins implicated in the aphid transmission of cereal yellow dwarf virus. PLoS One. 7(10): e48177.doi:10.1371/journal.pone.0048177. (*Authors contributed equally.)

    Jurick II, W. M., Vico, I. Gaskins V. L., Peter, K. A., Janisiewicz, W. J. and Conway, W. S. 2012. Nutritional cues and ambient pH modulate the in vitro activity a of polygalacturonase isozyme produced by Penicillium expansum. 2012. Archives of Phytopathology and Plant Protection. 45(9): 1101 - 1114.

    Peter, K. A., Gildow, F., Palukaitis, P. and Gray, S. M. 2009. The C-terminus of the polervirus P5 domain limits virus infection to the phloem. Journal of Virology 83 (11): 5419 - 5429. (*Cover illustration for issue.)

    Peter, K. A., Liang, D., Palukaitis, P. and Gray, S. M. 2008. Small deletions in the potato leafroll virus readthrough protein affect particle morphology, aphid transmission, virus movement and accumulation. Journal of General Virology 89 (8): 2046 - 2054.


    Ph.D. Plant Pathology, Cornell University M.S. Plant Pathology, Cornell University B.S. Agriculture, University of Delaware, cum laude, Degree with Distinction