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 diagnose the problem. You may have a disease causing fungus, such as Armillaria, Phytophthora, or Verticillium. The solution may be as simple as planting trees and shrubs that do not get the disease. Improving soil drainage may solve the problem. 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 or 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. 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. Special research projects are available. Many disease control strategies can be pre-tested in the lab, saving you time and energy.

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 $140/hour
Site Visit $140/hour
Legal (depositions, etc.) $300/hour


Typical Charge (per sample)
Site Visit with Diagnosis $200 (typical)
Fungal Diagnosis $70
Bacterial Diagnosis $70-$100
Fungal and Bacterial Diagnosis $70-$100
Turf Diagnosis $75
Conk/Mushroom ID $70

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.

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 pathologist 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 from a small set of tissues showing symptoms from the plant.  A confirmatory diagnosis would require pathogenicity tests which are very time and resource consuming and are generally not done for a known disease.  The fee is charged for the diagnostic process.  Results may be negative.

Disease Handouts

Handouts are available on the following diseases:
Armillaria root rot
Armillaria resistant plants
Verticillium Wilt
Verticillium resistant plants
Phytophthora root rot