A Laboratory and Field
Diagnostic Service

780 Palmer Road
Walnut Creek, CA  94596-6017
phone/fax (925) 937-3841

Disease diagnosis and horticultural consultation.
Landscape and garden.


Solutions for Your Home Garden Problems

If the trees and shrubs in your landscape are looking unhealthy or dying, you may have a disease or cultural problem. The first step to improve plant health is to determine just what is the problem. You may have a disease causing fungus, such as Armillaria, Phytophthora, or Verticillium in your soil. The solution may be as simple as planting trees and shrubs that do not get the disease. Improving soil drainage may solve the problem. A fungicide may be helpful. Once the cause of the disease is determined, the proper management techniques can be recommended. If no disease is present the poor vitality of the tree of shrub may be due to improper cultural conditions. Selection of plants that will do well in your yard may solve the problem.

A site visit to your home is recommended for a thorough evaluation of your landscape situation. It is difficult for a homeowner to collect the proper plant sample for a diagnosis. Plant samples are cultured in a laboratory to confirm the diagnosis.

Common disease or cultural problems identified include:
  • Armillaria root rot
  • Phytophthora root rot
  • Verticillium wilt
  • Cypress canker
  • Sudden Oak Death
  • Fire blight
  • Slime flux
  • Salt damage
  • Conk/mushroom Id.
Commercial Turf and Landscape Solutions

To keep ahead of your turf disease problems, an accurate diagnosis is essential. Spraying with the wrong fungicide wastes money and adds unwanted chemicals to the environment. A site visit will determine your disease or cultural problems and lead to an attractive landscape and a happy client.

In addition to tests for landscape tree and shrub problems, the following turf diseases are commonly cultured:

  • Pythium blight
  • Brown patch
  • Snow mold
  • Anthracnose
  • Dollar spot
  • Patch diseases
Commercial Nurseries Research

An early and accurate diagnosis of your disease problems can save you from large crop losses. We specialize in bacterial disease diagnosis. Special research projects are available. Many disease control strategies can be pre-tested in the lab, saving you time and energy. For instance, fungal or bacterial strains from your facility can be cultured and tested against pesticides to determine if resistance is present. This saves money by preventing the use of ineffective pesticides.

Pathogens commonly investigated include:

Tests available for:

  • Pythium
  • Rhizoctonia
  • Sclerotinia
  • Seed testing
  • Bacterial diseases

Collecting & Shipping Specimens for Diagnosis

Principal Diagnostician: Luellen Pierce

MS in Mycology, 1972, University of Wisconsin

Fee Schedule
Lab Work/Research $110/hour
Site Visit $110/hour
Legal (depositions, etc.) $250/hour


Typical Charge (per sample)
Site Visit with Diagnosis $160 (typical)
Fungal Diagnosis $55
Bacterial Diagnosis $55-$75
Fungal and Bacterial Diagnosis $55-$85
Turf Diagnosis $60-150
Soil (per pathogen) $60-$75
Conk/Mushroom ID $55

The fee is charged for the diagnostic process.  Results may be negative.

Fungal Diagnosis
One plate of a non-selective media is used.  In addition if the symptoms indicate it, one plate each of one or two selective media are used.  Affected tissue is placed on the medium.  In two to seven days the plates are examined microscopically for fungal pathogens.  Pathogens are usually identified to the genus level.  An additional fee may be charged if identification to species is requested.

Bacterial Diagnosis
The specimen is macerated and streaked on plates for bacterial growth. One non-selective and two to three selective media plates are used.  Additional physiological tests are needed for identification, which takes two days to a week.

Turf Sample
The turf sample is examined microscopically for visible pathogenic fungal spores.  It is then plated out on one to three media for fungal growth.  In two to seven days the plates are examined microscopically for fungal pathogens.  A straining technique is used to detect patch diseases.

Soil Pathogen Tests
A selective medium is used depending on the suspected pathogen.  Call to make sure a soil test is available for the desired pathogen.  Plant samples are preferred to soil samples to detect a pathogen.

Research projects concerning disease control strategies or a desired topic are available.

Site Visit
Site visits allow a better overall picture of your disease problem.  It is very difficult for a non-pathologist to select the proper tissue for analysis.

Sudden Oak Death
The Phtophthora that causes Sudden Oak Death is difficult to isolate and culture.  It is highly recommended that a apthologist visit the site to evaluate the symptoms and collect the sample for culturing.

Due to limits of time and resources a presumptive diagnosis is made in diagnostic clinics.  Diagnostic work is not inherently very quantitative.  Generally only a small percentage of the total sample is used for isolation.  Representative pieces of the tissue showing pathogenic symptoms are planted on the agar media.  The procedure is analogous to a political opinion poll that comes to a conclusion based on a small sample of the total number of voters.  In diagnostic work we also come to a conclusion as to the cause of a plant disease based on the organisms that grow that grow from a small set of tissuesshowing symptoms from the plant.  A confirmatory diagnosis would require pathogenicity tests which are very time andresource consuming and are generally not done for a known disease.  The fee is charged for the diagnostic process.  Results may be negative.

Disease Handouts

Luellen has created one-page handouts, each describing information and management tips on a particular disease. They can be mailed to you at a cost of $1.50 each, or you can order the entire set of 32 for a total of $30. Presently, they are not available electronically. Here is an example in jpeg format.  Please remember that it, as well as all the others, is copyrighted, and cannot be reproduced without permission.

The Handouts are available for

To order, email Plant Disease Diagnosis, or call or fax (925) 937-3841.