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NC State Extension

Submitting Samples From a Tree or Shrub in the Nursery

en Español

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potted shrubs in a nursery

A good sample is essential for an accurate diagnosis. Please follow these instructions carefully. The instructions on this page apply to sampling shrubs and trees from container-grown or field-grown nurseries.

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To sample for disease diagnosis

Note: In addition to the physical sample taken as described below, a few photographs showing the symptoms of concern and their distribution in the nursery can be helpful to the diagnosticians. Images can be uploaded to the database along with the sample information.

Sampling Small to Medium-Sized Trees or Shrubs

  • For container-grown material, submit one plant with moderate symptoms or 2-3 plants showing a range of symptoms.
  • Plants should be left in containers when bringing them to the PDIC, but when mailing you may choose to remove them from the container so that the root ball can be wrapped in a plastic bag and fastened loosely around the main stem. This prevents soil or potting media from getting on the foliage in transit. The whole plant can then be placed in a separate plastic bag before placing in a sturdy box.
  • Field-grown material can be dug and sent as described above. To mail a medium-sized tree (4-8ft tall), the main stem can be cut into numbered sections so that we can reconstruct it in the clinic.

Sampling Large Trees or Shrubs

  • If coming in person to the PDIC, you can bring trees and shrubs as large as your vehicle will allow. With open-bed trucks or trailers, cover the plants to avoid wind damage en route. Please call (919-515-3619) when you arrive so we can meet you in the parking lot and subsample the parts needed for our analyses.
  • When it’s not possible to submit entire plants, representative symptomatic parts can be submitted in the same way as described for landscape trees and shrubs. If possible, the lower portion of the main stem – including the graft union, if any – and upper part of the root system should be included, along with the adhering soil.

Pathogen detection in planting material

While we understand growers’ concern that seeds, plugs, or liners may harbor pathogens, we do not as a general rule accept samples of plants or planting material that appear to be healthy. This is for three reasons. First, there are dozens of potential pathogens, so we need the symptoms as a guide for the diagnostic process. Secondly, when pathogens are present without symptoms, they tend to be at low levels, requiring particularly sensitive screening techniques. Third, the selection of the sample is critical in those cases, to reduce the chance of a negative result that doesn’t truly reflect what’s going on in the greenhouse or nursery. If you have any specific questions about this policy, feel free to contact us at 919-515-3619 or via email at