2015 Search for Excellence Awards – Community Service — 2nd Place Winner

Fairfax Master Gardener Diagnostic Lab: Serving the Public for 34 Years

Fairfax Master Gardener Diagnostic Lab: Serving the Public for 34 Years

The Fairfax County Master Gardeners Association (FCMGA) Diagnostic Laboratory placed second in the Community Service Category of the 2015 International Master Gardener Search for Excellence.

The Lab has been in operation since 1981. Its purpose is to solve difficult plant identification, insect, and disease problems for the general public in Fairfax County, Virginia.  To our knowledge it is the only diagnostic laboratory operated by a Master Gardener group in the state of Virginia.

There is one Virginia Cooperative Extension (VCE) horticultural agent for Fairfax County, Virginia.  She serves a population of over 1.1 million residents.  Master Gardeners, numbering over 350 in Fairfax County, are a great force multiplier for the extension agent.  The Lab supports this effort by diagnosing problems that require deep knowledge and experience. The Lab is an important adjunct to the weekly plant clinics operated by FCMGA from May to September at 13 farmers markets and 5 public libraries throughout the county.  That’s well over 300 plant clinics per year!  In addition the Lab handles diagnostic requests that come directly from the (VCE) office in Fairfax from residents and landscape companies.  Services of the Lab and FCMGA are available free of charge.


Lab veterans Ted Stroup and Priscilla Baetke examine a new sample



The essential ingredient for a successful diagnostic laboratory is expert Master Gardeners with a passion for horticulture and public service.  Our Lab volunteers have an average of 17 years’ experience with FCMGA; the longest tenure is 37 years.  They are among the most knowledgeable Master Gardeners in the FCMGA.  In 2013 14 of FCMGA’s most experienced Master Gardeners volunteered 818 hours of service to this activity.


Samples that our Master Gardeners are unable to diagnose or identify at a plant clinic are referred to the Lab.  The Lab usually provides identifications, diagnoses, and advice within a week, most often in a report that is emailed directly to the client.  Responses typically contain an explanation of the problem, diagnostic keys to recognizing it, and a tutorial to help the client address the current problem and avoid similar problems in the future.  This advice includes recommended cultural practices and controls.



Our lab is equipped with two microscopes.  The microscope is a necessity for identifying mites, small insects, various insect eggs, and many fungal pathogens whose fruiting bodies cannot be seen by the unaided eye.  Diagnosticians have access to four computers for report preparation and research. There is a bookshelf containing useful references and a refrigerator for storage of samples. The Lab is housed in approximately 225 sq. ft. of space provided by the Merrifield Garden Center. Finally, the Lab has a variety of forms and instructions developed over the years to facilitate the delivery of its services.


In a typical year the Lab diagnoses over 300 samples (i.e., what is the problem with my plant?).  The diagnoses consist of over 100 different pathogens or causes, primarily fungal diseases (very common here in the humid Middle Atlantic region), insects, mites, and cultural problems.  Prominent among the fungal problems are several types of leaf spot, conifer tip blights, powdery mildew, sooty mold, and downy mildews.

Spider mites of several kinds tend to be the leading invertebrate problem in a dry year. Rose slugs, lacebugs, and various types of scale, led by cottony camellia scale, are the most common insect problems. In a year with unusually high rainfall most cultural problems are related to wet soil.

In a typical year the Lab handles 150 to 200 identification requests (i.e., what plant, insect, mushroom or other object is this?), the vast majority of which are plant samples.


Each diagnostic report provides a mini-lesson in IPM to the client who submitted the sample.  Fairfax County is located in the watershed of the environmentally threatened Chesapeake Bay. Reduction in the use of pesticides and fertilizers is an important public objective in our area.  Implementation of the Lab’s IPM-based advice means clients are not using pesticides and fertilizers unless absolutely necessary and only using them at a time when they would be effective.  When a pesticide is used, it is one whose effectiveness against the diagnosed problem has been proven through university extension service research.


Priscilla Baetke performs microscopic analysis.

Some clients reply directly to the Lab’s email report vowing to follow the advice.  Others return to FCMGA’s weekly plant clinics to discuss what they have done, ask further questions, and express their gratitude for the service.  Some return on multiple occasions during the year with more problems for the Lab to diagnose.


The Lab publishes a variety of reports based on lab findings.  For the 2013 Plant Clinic season, the Lab prepared a series of “Monthly Preview” documents, each highlighting problems we would expect to see at clinics in the coming month.  The previews are now published on our public website.

In addition, the Lab produces a “Lab Notebook”, usually with the assistance of a summer intern whose salary is partially funded by the FCMGA.  The reports, published every 1 -3 weeks from May to August, describe the lab’s latest findings.  The Lab Notebooks are replete with descriptions, photos and statistics to arm FCMGA master gardeners and professional landscape maintenance personnel who subscribe to this free service with the information they need to deal with the myriad of plant problems we encounter in the Middle Atlantic region.


The Merrifield Garden Center, one of the leading independent garden centers in Virginia, provides physical space for the Lab and connectivity to the Internet.  Merrifield’s support in the interest of sound horticultural practices contributes significantly to the success of the Lab and to FCMGA in general.



Tags: ,

Comments are closed.