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Plant Pathology Program

The Plant Pathology Program, within the Division of Plant Health, Bureau of Plant Industry, is responsible for the diagnosis of plant diseases in the Commonwealth, and the control of plant diseases of regulatory significance. There are three primary components to plant pathology program work:  Survey, Diagnostic Services, and Certification.

A primary function of the Plant Pathology Program is to provide diagnostic support to PDA Plant Inspection staff who inspect nursery stock being offered for sale in the Commonwealth. If nursery stock is suspected of harboring a plant disease, Plant Inspectors work with specialists in Plant Pathology to properly diagnose the disease and determine if it should be controlled before the nursery stock can be sold. (For more information, see Plant Merchant Certification.

Under Pennsylvania's Plant Pest Act, responsibility for control of plant pests extends to any environment in the Commonwealth, so the Plant Pathology group may address disease in any area of agriculture or the environment.  This is done through three primary activities:


Plant Pathology survey work is linked closely to the Cooperative Agriculture Pest Survey (CAPS), a USDA program that identifies national, regional, and state plant pests of concern and provides program support to survey for those pests.  In Plant Pathology, pests of current survey interest include Ralstonia blight of geranium, P. ramorum (sudden oak death), and plum pox virus.

Plant Disease Diagnostic Laboratory (PDDL)

The PDDL is a full-service plant disease diagnostic laboratory, able to test for all types of plant disease organisms (bacteria, fungi, nematodes, and viruses) by a range of techniques, including microscopy, culture/isolation, serological tests, and molecular tests.  The laboratory has a database of plant diseases found in Pennsylvania across the years, as well as an extensive culture collection of bacterial and fungal isolates.  The PDDL is a sister laboratory to Penn State University's Plant Disease Clinic: while the PSU lab is charged with assisting homeowners and farmers with disease problems, PDA's lab accommodates samples from regulatory survey programs.  Both labs work together, however, to answer the needs of the Commonwealth, and are both participants in the National Plant Diagnostic Network.

Specialized Certification Programs

In cases where plants are produced from a relatively small number of stock plants, it is especially important to be certain that the stock plants are as healthy as possible.  If a stock plant carries a virus, it may not be readily apparent in the stock plant, but may cause economic problems with the crop of plants produced from that stock plant.  For this reason, clean stock programs have been initiated. Specialized virus certification programs are available in Pennsylvania for fruit trees and for geraniums. Pennsylvania is an active participant in the National Clean Plant Network.