ISSUE 7   June 15, 2006


We often get questions on what to include with a sample, and how and where to submit it. Below is a summary of what makes a good sample. These guidelines are probably applicable to samples submitted to county extension offices as well, but you might want to call your county extension agent first to see if they can handle the sample, and if so, how they want to receive it. We recommend checking with your county extension agent before submitting a sample to the lab, because their schedules will sometimes allow them to adequately respond to your questions. However, on occasion, the schedules of county agents don’t permit them to be able to adequately handle a sample. In those situations, they might refer samples to the lab. A $15 diagnostic fee usually applies, unless your county agent has remaining vouchers for free diagnoses. If ELISA testing is needed (a special test for detecting plant pathogens, such as certain viruses), an additional $10 fee per test applies. Submitters are invoiced when written reports are completed, so there is no need to send pre-payment. These fees are used to help offset the costs incurred by the lab (no funds are appropriated for equipment, lab supplies, and reagents).

Plants: For general plant problems, try to send several affected plants showing a range of symptoms. Dead plants rarely are informative – avoid sending completely dead plants. Try to send entire plants, when feasible, since some above-ground symptoms can be attributed to a problem with the lower stem or roots. When digging plants, try to keep the roots intact with the soil, as a root ball, to help prevent the sample from drying out. The root ball should be wrapped in a separate plastic bag (tied off at the stem) to prevent soil from coming in contact with leaves. The foliage should be wrapped in dry paper towels to absorb moisture (to prevent decay), and the entire sample should then be placed in another plastic bag. Resealable bags work well for this. Do not allow leaves, paper tags, or labels to come in contact with soil.

Mushrooms and fruits: Wrap mushrooms or fruits in dry paper towels or newspaper and place in sturdy box to avoid crushing.

Insects: Send small insects, such as beetles and ticks, in vial of alcohol. Surround large insects (dead), such as moths, with cotton and send in a sturdy box (like a shoe box). Please DO NOT SEND LIVE INSECTS. Insects should be dead. The exception to this is plant pests such as aphids, spider mites, psyllids, and others that are associated with their plant host – these can be submitted as described above for plants.

Turfgrass samples: Plugs that are about 3-5" in diameter and deep enough to include the roots (usually about 3") are ideal. The best sample consists of a completely diseased plug, a healthy plug, and a plug from the transition zone between diseased and healthy turf.

Soil samples for nematode extraction or root rot indexing: 1. Use a soil probe to collect samples, 6-8 inches in depth. 2. Using a zigzag pattern, collect 10-20 soil cores per every 10 to 20 acres. 3. Collect cores from areas of similar soil type and crop history. 4. Dump cores from each 10-20 acre set into a bucket or tub and mix thoroughly. 5. For nematode screening, send 1 pint (2 cups) of mixed soil in a soil sampling bag or plastic zippered bag. For root rot (e.g. Aphanomyces) indexing, send about 1 gallon (32 cups) of soil per 10-20 acre set. Label the bags with a permanent marker. Don't allow paper labels to come in contact with soil. 6. Store sample in a cool, dark place until shipped to the lab.

Dutch elm disease testing and other vascular wilt testing: Live, symptomatic branches that are at least 1" in diameter and 6-8" long should be submitted, with leaves attached. Causal agents typically cannot be isolated from completely dead material.

How and where to send samples: Ship or hand-deliver samples as soon as possible after collecting. For the eastern half of North Dakota, samples usually arrive within 24 hours with regular mail. For more distant areas, next-day mail is recommended, particularly for high risk pests. Mailing address: NDSU Plant Diagnostic Lab, 306 Walster Hall, Fargo ND 58105. Physical address: 206 Waldron Hall, NDSU, Fargo.

The lab form, a campus map, and the above information are available online at



Below is a summary of samples diagnosed in the past week:




Woolly Elm Aphid

Ash (ornamental)


Ash; Green

Ash anthracnose

Ash; Green

Herbicide Injury; Exposure

Maple, Silver

Cottony Maple Scale

Maple, Sugar

Cottony Maple Scale




Wheat Streak Mosaic Virus

multiple hosts

Growth Regulator Effect


Environmental Stress; Problem


Eriophyid Mites


Powdery Mildew

Buckthorn; Common

Oat Crown Rust

Spruce; Blue

Drought Stress Damage

Spruce; Blue

Rhizosphaera Needle Cast

Spruce; Blue

Conifer Spider Mite

Spruce; Blue

Environmental Stress; Problem

Spruce; Blue

Spruce Needleminer

Beet; Sugar

Rhizoctonia Root Rot

Beet; Sugar

Aphanomyces root rot

Kasia Kinzer
NDSU Plant Diagnostic Lab

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