Kari A. Peter, Ph.D.

  • Associate Research Professor, Tree Fruit Pathology
Kari A. Peter, Ph.D.
Penn State Fruit Research and Extension Center
290 University Dr.
P.O. Box 330

Biglerville, PA 17307
Work Phone: 717-677-6116
Fax: 717-677-4112

Areas of Expertise

  • Apple and pear diseases
  • Peach, cherry, other stone fruit diseases
  • Integrated tree fruit disease management

Connect with Kari A. Peter, Ph.D.



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

Areas of interest

Commercial tree fruit disease management: 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

Current Graduate Students

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 and fifth for peaches in the United States. I am located at the Penn State Fruit Research and Extension Center in Biglerville, PA in Adams County, where 75% of the tree fruit in PA are grown. (To note: we are in south central PA and approximately 120 miles south of main campus in University Park, PA.) 

My Extension Program focuses on educating commercial growers about effective, sustainable disease management strategies for important diseases problematic in the region. This includes regular participation in winter educational meetings and spring/summer twilight 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 commercial 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 season-long management strategies for controlling bacterial diseases, specifically fire blight and bacterial spot of peach, and apple fruit rot diseases occurring during the season and while storage; identifying possible emerging pre- and postharvest apple fruit rots, as well as monitoring for exotic pathogens; and working closely with agrochemical companies for evaluating chemistries and alternative products for suitability and efficacy in controlling tree fruit diseases under Pennsylvania environmental conditions.


Jurick, W. M., Macarisin, O., Gaskins, V., Janisiewicz, W. J., Peter, K. A., & Cox, K. 2019. Baseline Sensitivity of Penicillium spp. to Difenoconazole. Plant Disease. Plant Disease. 103: 331-337.

Wu, G., Jurick, W. M., Lichtner, F. J., Peng, H., Yin, G., Gaskins, V., Yin, Y., Hua, S. S. T., Peter, K. A., & Bennett, J. 2019. Whole-genome comparisons of Penicillium spp. reveals secondary metabolic gene clusters and candidate genes associated with fungal aggressiveness during apple fruit decay. PeerJ. 7:e6170 http://doi.10.7717/peerj.6170

Klee, S., Mostafa, I., Chen, S., Dufresne, C., Lehman, B., Sinn, J., Peter, K. A., & McNellis, T. W. 2018. Erwinia amylovora yjeK mutant exhibits reduced virulence, increased chemical sensitivity, and numerous environmentally dependent proteomic alterations. Molecular Plant Pathology. 19(7): 1652-1666.

Lui, H.-W., Wu, L.-P., Nikolaeva, E., Peter, K. A., Liu, Z., Mollov, D., Cao, M.-J., & Li, R. 2018. Discovery and molecular characterization of a new luteovirus identified by high-throughput sequencing associated with rapid apple decline. Virology Journal. 15: 85-93.

Jurick II, W. M., Peng, H.,  Macarasin, O., Gaskins, V. L., Macarasin, O., Yu, J., Janisiewicz, J. E., Peter, K. A. 2017. Dominant Selectable Markers for Penicillium spp. Transformation and Gene Function Studies. Fungal Genomics and Biology. 7:153 doi:10.4172/2165-8056.1000153

Jurick II, W. M., Macarasin, O., Gaskins, V. L., Park, E., Yu, J., Janisiewicz, J. E., Peter, K. A. 2017. Characterization of postharvest fungicide-resistant Botryis cincerea isolates from commercially stored apple fruit. Phytopathology. 107 (3): 362 - 368.

Nikolaeva, N., Welliver, R., Rosa, C., Jones, T., Peter, K., Costanzo, S., and Davis, R.E. 2017. First report of apple (Malus domestica) as a host of ‘Candidatus Phytoplasma pruni’ in the United States. Plant Disease. 101 (2): 378.

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.