Did you know that over 30% of Minnesota is forested? So, while our great state is known as “The Land of 10,000 Lakes,” we love our trees, too!

Minnesota is home to 53 native tree species, including the White and Black spruce. Black spruce mainly populates Minnesota’s bogs and is ideal for wet soil while White spruce is popular for landscaping/ornamental use, providing beauty, privacy, wind protection, and cleaner air, not to mention Christmas trees. Another popular spruce in our area is the disease-resistant Norway spruce.

Unfortunately, spruce tree pathogens are wreaking havoc on our precious spruce trees, causing too many to become deformed or die prematurely each year. To keep your spruce trees safe and healthy, here’s a guide to common Minnesota spruce tree pathogens and how to prevent and treat them.

Needle Cast Diseases

Rhizosphaera Needle Cast

Symptoms & Identification

This common disease causes needle discoloration, death, and the shedding of needles in spruces. In the spring/summer, if your spruce is showing green tips (where the new growth is) and brown or purple color on the older needles, take a magnifying glass to your needles.

Your spruce may be affected by the fungal infection Rhizosphaera needle cast if tiny black bumps in neat rows are found on the green, brown, or purple needles. These black bumps are actually fruiting bodies that release spores during wet weather, spreading the disease to other trees.

Treatment Options

The best time to treat Rhizosphaera needle cast is in the spring. Optimal treatment includes two fungicide sprayings, one at the end of May and the second spraying four to six weeks later. A variety of fungicides are effective, including copper fungicides.

Stigmina Needle Cast

Symptoms & Identification

Stigmina needle cast looks just like Rhizosphaera, necessitating a microscopic analysis by our arborists to properly diagnose it. Affecting White, Black, Blue, and Norway spruce trees, Stigmina needle cast is a fungal disease caused by the pathogen Stigmina lautii.

Treatment Options

For homeowners, we recommend removing the infected spruce trees, though annual fungicide spraying by our tree experts can also be effective.

Canker Diseases

Cytospora Canker

Symptoms & Identification

Caused by the fungus Leucostoma kunzei, Cytospora canker is a fungal disease that often affects large, mature spruces that are under stress from drought, ice damage, insects, or other issues.

While it rarely kills spruces, this disease can severely deform them over time. Symptoms include dead or dying branches throughout the tree, along with sunken cankers close to the trunk. These cankers are covered by a thick layer of resin, which often forms drips and bumps.

Treatment Options

Removing the infected tree is the fastest way to contain the fungal infection. If the tree is salvageable, pruning out the sick branches during dry weather only can also help. Keep in mind that pruning is a long-term commitment, as it can take several seasons to significantly reduce the problem.

For prevention, stick to planting native spruce trees, such as White spruce, for your landscaping projects. Colorado Blue spruce, for example, is easily stressed in Minnesota and prone to Cytospora canker.

To minimize stress, always plant your spruces in full sun in moist, well-drained soil topped with mulch. Water your spruce during dry periods and check for cankers every year.

Phomopsis Canker

Symptoms & Identification

Phomopsis canker causes spruce leaves to wilt and brown. Obvious signs include blight (the browning and dieback of young shoots) and cankers (dark, sunken areas) on stems, which can ooze resin or sap.

Treatment Options

Consistent, frequent, and careful pruning away of infected trees or branches (during dry weather) can help contain the infection. Take special care to cut several inches below the infection at the branch collar, and avoid leaving any stubs.

Fungicides applied in the spring can also help protect new shoots from infection. Keep in mind that disease control greatly depends on managing the underlying stressors that enabled the disease to take hold, such as drought or insects.

Root Rot Diseases

Armillaria Root Rot

Symptoms & Identification

A telltale sign of Armillaria root rot is honey-colored mushrooms at the base/roots, along with encrusted resin, which can extend up into the trunk. You’ll also notice yellow and brown foliage, slow growth, and patches of wood that look white, soft, and stringy.

Treatment Options

Prompt professional treatment of root rot is crucial to prevent falling trees during storms. Treatment includes removing the infected wood and root systems, reducing tree stress, mulching soil at the tree base, and removing unstable trees.

Our expert arborists can determine the condition of your tree and the safest, most effective solution.

Phytophthora Root Rot

Symptoms & Identification

Common in waterlogged soil, Phytophthora root rot is a microscopic organism that causes green spruce trees to become dull and eventually turn gray and brown before they die.

Other signs of this root rot include dieback, sparse foliage, and black bark discoloration. Our arborists will examine the root system for signs of decay and conduct testing to confirm the cause of the rot.

Treatment Options

Our professional arborists can help your sick spruce using irrigation management, fumigation, fungicides, and prevention methods, including planting disease-resistant spruces.

Spruce Budworm

Symptoms & Identification

Each year, Spruce Budworm is responsible for killing acres of Minnesota spruce. This native parasitic insect loves to feed on the new growth tips of needles.

In its early stages, affected spruces will show damage on the outer branch shoots in the upper crown, with partially eaten needles that are webbed onto branch tips, which turn reddish-brown.

Treatment Options

For small-scale infections in yard trees, professional pesticide applications can be quite effective. Removing infected trees is also recommended if the infection has progressed too far, since dead or dying trees are a fire hazard.

Prevention Strategies

At Bratt Tree Company, our licensed arborists have decades of tree care expertise and understand that prevention is the best strategy concerning spruce pathogens. To keep your landscape in prime condition, we recommend:

• Tree selection: Planting native white spruce and other proven Minnesota thrivers will set you up for long-term landscaping success.
• Proper planting and care techniques: Plant in early spring or early summer to give your trees a chance to establish a hearty root system. Water regularly and deeply during the first year. Plant in moist, well-drained soil and cover the tree bases with mulch/compost. You can also give your spruce a boost by applying a slow-release fertilizer in the spring, but be sure to water well after applying.
• Routine inspections: Look for signs of damage and prune away dead or damaged branches.
• Winter protection: Give your spruces one last deep watering before winter to sustain it through the freezing months.

Seek Professional Help From Arborists at Bratt Tree Company

Don’t wait if your spruce tree is showing signs of distress. Early detection is the key to saving your spruce. Call us ASAP if your tree stops growing, starts to wilt, fades in color, or branches are dying.

Our ISA-certified arborists are backed by 30+ years of experience caring for all types of trees in the Twin Cities area and will always guarantee your satisfaction by providing:

• Upfront pricing
• Trained technicians
• Free estimates
• Proactive tree health solutions
• And more

Affordable and reliable help for your spruce is just a call away. Simplify your landscaping needs by contacting Bratt Tree Company today.