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Don't wait to diagnose spruce problems

Now is the time to treat for spruce needle cast diseases. Do you know what’s wrong with your spruce and how to treat it?  

M. Grabowski, UMN Extension Educator

spruce tree branch lying on the ground with brown, dead needles
Spruce tree suffering from Rhizosphaera Needle Cast.
M. Grabowski, UMN Extension
Many spruce trees across Minnesota have brown or missing needles along with dead branches. This damage can be caused by a variety of problems including needle cast or needle blight diseases, branch cankers, insect pests, mites, or environmental conditions.

Although management options are available for many of these problems, each problem has its own unique solution. The first step in correcting a spruce problem is getting a correct diagnosis.

Send a sample for diagnosis now

Treatment for Rhizosphaera Needle Cast or Stigmina Needle Cast, two common diseases of spruce trees in Minnesota, need to begin at this time of year. Before you treat you MUST know which disease problem your tree has! Unfortunately it is not possible to diagnose either of these disease problems without a laboratory analysis. Both fungal pathogens cause needles to discolor or fall off. Both fungal pathogens make tiny black spore producing structures along the needle. Although these spore producing structures can be seen with a hand held magnifying glass, it is not possible to distinguish between the two pathogens with a magnifying glass alone.

Where to send a sample

You can send a plant sample to University of Minnesota Plant Disease Clinic on the St. Paul campus. Samples can be dropped off in person or sent in the mail. There is a fee for diagnosis. Check the web page for current prices.

What to send

Send a branch that has live but discolored needles. The branch needs to be long enough to include needles from the past 3 to 4 years of growth. A branch that is 1 to 2 feet long is usually sufficient. This year’s needles will be pale green, soft, and at the very tip of the branch. Previous years needles will be further down the branch with a ring of rough brown bud scales on the twig separating each year of growth. Keep the sample in a cool dry location until it can be sent.

Fill out the online sample submission form and include it with the plant sample.
closeup of spruce branch with needles that have yellow, shiny areas and a bumpy growth on the main twig that has a yellow arrow pointing at it
Bud scales on a spruce twig.
UMN Plant Disease Clinic

three yellow arrows point at three different locations on a spruce branch lying on a black background
A spruce branch with three years of growth.
UMN Plant Disease Clinic

How to send a sample

Wrap the branch in dry newspaper and then plastic before placing it in a box for mailing. It is best to mail the sample early in the week to avoid having the plant sample sit in a storage facility over the weekend. Samples brought directly to the clinic do not need to be packaged.

What happens to plant samples at the clinic?

The plant pathologists at the UMN Plant Disease Clinic carefully inspect every plant sample submitted. Diagnosticians use a variety of techniques to identify the pest or pathogen causing the problem including microscopy, culturing and DNA analysis.

conifer branch with very sparse needles lying on a white background
Needle discoloration and loss caused by Stigmina Needle Cast.
M. Grabowski, UMN Extension 

How do I get the results?

The results will be sent to you via email, mail, or fax. You choose by marking a box on the submission form.

Treatment options 

The results will include the name of any pests and pathogens found on the plant sample and information about research based management options available to you. More information about how to treat common spruce diseases can be found at the UMN Extension website.

If you do not want to treat your trees yourself you can hire an arborist. Arborists are tree care professionals that can work with you to provide the best care for trees on your property. 

To find a certified arborist who works in your area, you can use the Find an Arborist tool from the International Society of Arboriculture.

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