Blue Spruce Dying From the Bottom Up in Michigan: Causes and Fixes

MSU plant pathologists describe it plainly in their published research. Starting in the early 2000s, spruce trees in Michigan began showing needle drop at the base of the tree and branch death that slowly moved upward. A 2013 survey found the problem common throughout the Lower Peninsula. A follow-up study describes the typical Colorado blue spruce: needles thin out on the lower part of the tree starting at the branch tips, then whole branches die, and the dieback works its way up over several years.

Spruce decline is not one disease. When MSU Extension experts answer homeowner questions about dying spruce, they list a group of problems that tend to pile on together: needle cast fungi, tip blights, and canker diseases that girdle branches. A tree can have one of them or all of them, which is why two spruces in the same yard can look sick in slightly different ways.

Colorado blue spruce comes from the Rocky Mountains, where the air is dry and the trees are spread out. Southeast Michigan is the opposite. An MSU Extension expert answering a Michigan homeowner put it simply: our humid climate and the habit of planting spruce close together in rows create conditions where fungal diseases do far better than they would in a drier region. Illinois Extension goes further on Cytospora canker, noting that it shows up on spruces planted outside their native range.

Stress makes all of it worse. Penn State Extension calls drought the critical trigger for Cytospora canker, and says the fungus can sit in a tree without symptoms until a dry stretch sets it off. Add heavy clay soil that stays wet in spring and bakes hard in August, and a blue spruce in a Livonia or Canton backyard is living under steady pressure. That is why the trees often look fine for their first 10 or 15 years and then start to slide.

Rhizosphaera needle cast is a fungus that infects the needles themselves. University of Minnesota Extension describes the classic look: new needles at the branch tips stay green while the older needles behind them turn purple to brown and drop in late summer or fall. The Morton Arboretum notes that Colorado blue spruce is particularly susceptible and can be severely damaged. Norway and white spruce are more resistant.

The telltale sign is on the needle. Pull a few discolored needles and look at them with a hand lens. Rhizosphaera produces tiny black dots lined up in neat rows along the needle, like a string of pinheads. The spores spread in warm, wet weather, and new needles are the most vulnerable. Infected needles typically die the following year, which is why the damage seems to lag a season behind the wet spring that caused it.

The good news with needle cast is that the branch itself is usually still alive. A tuft of green at the tip means that branch can recover if new growth is protected.

Canker diseases kill the branch, not just the needles. Cytospora canker starts on the lowest branches and moves up. The Morton Arboretum describes needles taking on a purplish cast before turning brown and dropping, along with white resin running down the bark. Illinois Extension notes amber to white patches of pitch where cankers form and says it mostly hits Colorado and Norway spruces older than about 15 years. Penn State notes that small branches usually die within a year or two and larger ones over several years.

In Michigan there is a second canker player. MSU research found that fungi in the genus Diaporthe, older references call it Phomopsis, were the most likely cause of the cankers behind spruce decline in their statewide survey. These cankers are shallow and show up in the inner bark when you peel the outer layer back. In MSU's testing, Colorado blue spruce was the most susceptible, followed by Norway spruce, then white spruce. Black Hills, Serbian and Meyer spruce were much less susceptible.

Start with the branch pattern. If the inside of a branch is bare but the tips still carry green needles, needle cast is the likely lead. If the whole branch is brown from tip to trunk, needles and all, and there is sticky or crusty white resin on the bark nearby, think canker. Scratch the bark on a dead branch with a thumbnail. Brown, dry tissue under the bark with a clear edge where it meets green tissue is a canker margin.

Many trees have both. The MSU Extension answers we reviewed repeatedly recommend sending a sample to MSU Plant and Pest Diagnostics before spending money on treatment, and Minnesota Extension says the same: lab confirmation first, because several problems look alike. For a tree that is worth saving, a diagnostic fee is cheap compared with two years of spraying for the wrong disease.

For needle cast, fungicides work if the timing is right. Minnesota Extension lists chlorothalonil, copper hydroxide or mancozeb applied when new needles are about half their full length, with a second application three to four weeks later. An extension answer on a dying blue spruce noted that recovery takes at least two years of consistent treatment. Spraying protects the new growth. It does not bring dead needles back. Spraying a 40-foot spruce thoroughly is a job for a licensed pesticide applicator.

For cankers, there is no spray. Illinois Extension, Penn State and the Morton Arboretum all say fungicides do not control Cytospora. The management is cultural. Prune out dead and cankered branches back to the trunk or a healthy side branch, only in dry weather, and disinfect tools between cuts with rubbing alcohol or a 10 percent bleach solution so you are not spreading spores up the tree. That is the kind of careful spruce pruning we do.

Beyond that, reduce stress. Water deeply during dry spells, mulch the root zone without piling it against the trunk, rake up fallen needles, and keep sprinklers off the foliage. Give the tree room. Extension advice calls for at least 8 to 10 feet between spruces, and more is better for airflow.

Here is the part people do not want to hear. Illinois Extension notes that feeding and good care can help a spruce fill small gaps with new growth, but large dead areas rarely recover. A spruce that has lost its bottom third is going to stay bare there. The branches above can stay healthy for years, but the tree you are left with looks like a lollipop, and a screen planted for privacy stops screening.

That does not mean the tree is dangerous. A spruce with dead lower limbs is mostly a looks problem. It becomes a safety question when the top starts dying, when dead wood is high over a roof or driveway, or when the whole tree has died and dried out.

Our honest rule of thumb: if the lower half is dead, cankers are showing up high in the crown, or the tree has stopped doing the job you planted it for, it is time to stop spending on treatment and plan a replacement. The same goes for a tight row of spruces where the whole row is declining. Taking out the worst trees opens up airflow, but if every tree has cankers, you are managing a slow loss.

If you are not sure whether a tree is still alive, scratch a twig and look for green under the bark. When it is time, we handle the removal, chip the brush, and can grind the stump so the spot is ready for replanting. A free estimate is also a good way to get a second opinion on a tree you are on the fence about. If the answer is that it has years left, that is what we will tell you.

An MSU Extension expert answering a Lapeer County homeowner with cankered blue spruces on clay suggested four replacements. White spruce is native to Michigan, handles clay and poor drainage, grows one to two feet a year, and holds up better against disease. Norway spruce grows one to three feet a year with dark green needles on orange stems. Eastern white pine, the state tree, is the fastest at two to three feet or more a year but gets huge, so it needs room away from buildings. Concolor fir keeps a blue-gray color, grows one to two feet a year, tolerates somewhat alkaline soil, and should stay out of frost pockets.

Two footnotes from what we read. MSU's own research found Norway spruce can still get Diaporthe canker, just less than blue spruce, and that Black Hills, Serbian and Meyer spruce were much less susceptible. And white pine does poorly near salted roads, which we cover in why pine trees turn brown. Whatever you choose, plant it in full sun with space around it. For more options, see our list of the best trees to plant in Michigan.

If your blue spruce is browning from the bottom up, we will look at it with you, tell you whether pruning buys it real time or whether it is time to plan a replacement, and give you a clear price for the work. Free estimates across Livonia and all of Southeast Michigan. Call (734) 788-8822.