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Horticulture and Home Pest News
Horticulture & Home Pest News is filled with articles on current horticulture, plant care, pest management, and common household pests written by Iowa State University Extension specialists in the Departments of Entomology, Horticulture and Plant Pathology.

Submitting Turfgrass Samples for Disease Diagnosis

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With the recent warm weather, lawns have turned vibrant green overnight. When brown patches appear in lawns during the season, lawn enthusiasts become discouraged. Many factors can cause poor health and browning of lawns - insects, diseases, animals, improper applications of lawn-care products, or environmental stresses such as heat and drought.

The correct diagnosis of the problem(s) involves thoughtful consideration of the history of area and recent activities. If an insect or disease problem is suspected, an accurate diagnosis may require microscopic examination of the leaves or roots. The usefulness of the diagnosis and management recommendations provided depends on the quality of the sample and the background information provided.

Clumps of completely dead grass are not adequate for problem diagnosis. There are several important tips to following when submitting turfgrass samples to the Plant Disease Clinic or Insect Diagnostic Clinic for problem diagnosis.

  • Include a section of turf with the roots that includes both sick plants and healthy plants, especially those that are on the edge of the problem area. The section(s) sampled should be at least 4 to 6 inches square.
  • Include a sketch or image(s) of the overall pattern of the problem area.

    1. Does the problem occur in patches? If so, are the patches small and round or large and irregular?

    2. Does the pattern suggest the involvement of equipment?

    3. Are the symptoms associated with building, trees, or sidewalks?

  • Provide as much background information as possible.

    1. What time of year did the symptoms first appear?

    2. How quickly has the problem progressed?

    3. What fertilizers and pesticides have been used? When were they applied and what rates were used?

    4. Is the lawn irrigated?

    5. When was the area sodded or seeded?

    6. Can the turf be easily pulled away from the soil?

    7. What were the rainfall patterns and temperature when the symptoms were first observed?

    8. Are any other plant species affected, such as weeds or flowers?

Collected samples can be quickly overrun with other organisms. If it is not possible to deliver a sample in person, it should be mailed immediately. Avoid mailing samples late in the week to reduce the chance they'll be caught in transit over the weekend. To keep the soil away from the leaves, wrap the sample in several layers of newspaper and secure in a sturdy box. Do not add any moisture to the sample. Place any insects that are collected in a vial with preservative (alcohol or hand sanitizer) and place the vial in the box with the sample.

Send samples with a suspected disease problem or unknown problem to:

Plant Disease Clinic
Iowa State University
323 Bessey Hall
Ames, IA 50011

A Plant Disease Identification Form can be found at http://www.extension.iastate.edu/Publications/PD31.pdf.

Send sample with a suspected insect-related problem to:

Insect Diagnostic Lab
Iowa State University
109 Insectary Building 
Ames, IA 50011
Dead turf sample
Dead turf sample that is inadequate for diagnosis. Instead, submit sample that includes both sick and healthy plants.
Turf browning example image
Example of an image that shows the overall pattern of browning.
Page References: 
42-43
Year of Publication: 
2006
Issue: 
IC-495 (8) -- April 19, 2006