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Debbie Miller, senior diagnostician and plant pathologist for the Davey Institute

How Tree Doctors Solve Common Tree Problems

October 1, 2013

A day in the life of a plant pathologist reveals how Davey's detectives determine tree care solutions.

My recent visit to the Davey Institute's diagnostics lab revealed more details about diagnosing sick trees and plants than I ever imagined existing.

The lab was much quieter than I anticipated. For a few minutes I was the only person in the room. While I waited for my personal tour guide to arrive, I observed a wide variety of plants in containers ranging in size and shape. As I continued leisurely weaving in and out between shelving units and storage bins, I noticed rows of shelves crammed with colorful, bound books with a variety of topics, from fungi to insect species.

Lab tops were speckled with microscopes prepped to inspect the petri dish samples Debbie Miller, senior diagnostician and plant pathologist, had collected that morning. When she entered the room to greet me, Miller opened the samples according to U.S. Department of Agriculture standards, in the bio-safety cabinet.

"Before we even get to this point of inspecting the actual samples we receive photos via email in order to see the kind of environment the sick trees and plants are in," Miller says. "Depending on what comes to us, usually I can immediately determine the disease or pathogen, or I have to do additional research. I always want to be 100 percent correct in my diagnosis. There are rare times I've encountered something I've never seen before."

crab apple leaf disease inspection
Plant Pathologist Debbie Miller inspects the leaf of a crab apple tree for common tree problems.


With a gleam in her eye, Miller motions me to come over to the microscope to observe a dying plant's leaf. I notice black speckles in various shapes and sizes. "Those are two different forms of apple scab fungus," she says. "One is the asexual form and the other is the sexual form."

Davey Institute lab microscope
Miller inspects four to 20 tree samples at the Davey Institute every day.

The lab receives plant material and tree samples from Davey offices across North America. Samples arrive in packaging according to USDA standards, which ensures pathogens do not escape and samples stay alive by the time they reach the Institute. Miller will inspect four to 20 samples every day, all while completing lengthy and informational reports to send back to the district managers who requested the inspections and tests. "Some of the samples take days, which can be very time-consuming," Miller explains. "After I diagnose them, I send my 'prescription' to managers to explain what the plant needs."

Her "prescription" includes observations and instructions to improve the plant's health--if it can, in fact, be saved. "When a prescription is written by the plant doctor, most of them are cultural--watering, fertilizing and, in the worst-case scenario, removal," Miller laments. "I hate when I have to prescribe removal

Davey Institute lab plant inspection
Miller inspects plant material for pests, diseases and other health problems.

because I love trees so much!"


Miller wraps up her day by storing the samples that weren't diagnosed in the refrigerator, putting plants on petri dishes that need cultured and making sure the microscopes are sterilized, turned off and have protective coverings placed on them.

"There can be long days, but I love every minute of it," Miller expresses. "It's a very detailed job, and it takes a certain amount of patience since the No. 1 most important thing to a diagnostician is observation. But it is an exciting job because every day there is a different mystery to solve."

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