The NCSU Plant Disease and Insect Clinic will accept samples of symptomatic boxwoods to check for the presence of the box blight pathogen, Cylindrocladium pseudonaviculatum (=Cylindrocladium buxicola). For this purpose, send only stem cuttings and leaves. Look for dark brown spots on leaf tips or elsewhere on leaves, dark brown to black streaks on otherwise green twigs or branches, and leaf drop. Three or four cuttings, each 6-8 inches long, can be sent to represent any given situation such as a particular landscape or nursery block. Samples should be double-bagged in closed plastic bags and shipped in a sturdy box. Do not add water, wet paper towels, or other moistened materials to the package. It is very important to indicate on the sample submission form which fungicides have been used during the last month, and approximately when they were applied. We need to give more time (up to two weeks) of moist-chamber incubation for samples which received fungicide treatments, since some fungicides will slow the growth of the fungus. If no fungicides were applied, this must be stated in the comments section of the form.

Due to sampling issues and current gaps in our knowledge about this new pathogen, we cannot provide any statement to third parties indicating that a nursery or other planting was found to be disease-free based on our sample results. Also, we will not check plants that do not appear to have any symptoms.

It is our policy at this time that box blight confirmation samples for nurseries* will be processed at no charge if submitted through the North Carolina Cooperative Extension Service (an extension agent) or the North Carolina Department of Agriculture and Consumer Services (an NCDA inspector), provided that the sample information is entered into the online PDIC database. In addition to the required fungicide information mentioned above, write "for box blight testing" in the comments section. Please note that these samples will be checked for box blight only. If roots and soil are sent with a sample, we will assume that a full diagnostic workup is requested — including a check for box blight, if symptoms warrant — and the usual fees will apply.

*We will of course continue to do box blight and other disease testing for commercial and residential landscapes, but the usual fee structure applies.

For more information about box blight, see the fact sheet here.


Last update: 10-Jan-2012 by M.J. Munster