The Threats Killing Twin Cities Trees — and How to Spot Them Early
Three killers are responsible for most of the tree loss in the southwest Twin Cities metro right now: emerald ash borer, oak wilt, and Dutch elm disease. A few other conditions round out the list. Here’s what each one looks like and what to do about it, from the experts at Natures Touch Tree Care & Landscaping.
Emerald Ash Borer (EAB)
Technically a pest rather than a disease, EAB is the metro’s most destructive tree killer. The beetle’s larvae tunnel under ash bark and starve the tree from the inside.
- Affects: All ash species
- Look for: Thinning canopy, woodpecker flecking, D-shaped exit holes, bark splits
- Action: Early infestations may be treatable; declining trees need prompt removal before the wood turns brittle
Oak Wilt
A fungus that plugs an oak’s water system. Red oaks can die within weeks; white and bur oaks decline more slowly. It spreads through root grafts between neighboring oaks and by beetles visiting fresh wounds.
- Affects: All oaks, red oaks most severely
- Look for: Leaves bronzing from the tips inward, rapid summer leaf drop starting at the top
- Action: Never prune oaks in spring/early summer; infected trees need careful, containment-focused removal
Dutch Elm Disease
The fungus that erased Minnesota’s elm-lined streets is still active. Elm bark beetles carry it to healthy trees, and it also moves through root grafts.
- Affects: American and other native elms
- Look for: “Flagging” — a single branch wilting and yellowing in summer — followed by crown decline
- Action: Fast removal with proper wood disposal protects surviving neighborhood elms
Apple Scab
A fungal disease that hits crabapples and apple trees, causing spotted leaves and early defoliation. It rarely kills, but repeated years of it weaken the tree. Resistant varieties and good fall cleanup help.
Bur Oak Blight
A more recent fungal problem affecting bur oaks, causing leaf browning and dieback that worsens year over year. A stressed bur oak also becomes more vulnerable to other pests, so diagnosis matters.
Spruce Needle Diseases
Needle cast fungi thin out spruce trees from the bottom up, leaving bare lower branches. Improving airflow and avoiding overhead watering slows the spread on landscape spruce.
Why Early Diagnosis Pays
Stress, drought, and disease can all look alike from the driveway. Catching the difference early is often the gap between treating a tree and removing it — and between losing one tree and losing several.
If something looks off about a tree on your southwest metro property, get an export’s opinion before deciding anything. Natures Touch Tree Care & Landscaping has been diagnosing and managing these diseases since 2010. Call 612-240-6355 for an assessment.
