Collection: Minnesota Tree Diseases, Pests, and Insects Gallery

What is going on with YOUR tree? The following photos and descriptions show Minnesota tree ailments, do your trees look like this? Maybe it's time to call Deblen. 


Tree diseases we see in Minnesota

Very contagious disease that affects most varieties of oak trees, can be confused with two-lined chestnut borer infestation. 


  • White Pine Blister Rust

An allergic reaction to currant or gooseberry juice brought to tree from squirrels or birds.



A fungus that can be confused with pine tip moth.

Affect pine trees from the roots up.


  • Chemical Damage

Chemical sprays and granular products can damage leaves through drifting and leeching into roots.


  • Cedar-hawthorn rust

  • Anthracnose


  • cherry tree black knot

  • Verticillium Wilt  A soil pathogen that infects the roots of the tree causing dieback in the corresponding branches above ground. Maple and lilac trees are very commonly affected.

Tree pests/Here are a few examples

  • Emerald ash borer This bug kills fast once it settles into a tree. It takes over the tissue that sends nutritious sap to the tree. Stop the sap, the tree is a goner.


  • Spongy moth (formerly gypsy moth) any time a leaf tree is defoliated the tree cannot photosynthesize. It needs leaves to survive. A strong tree can sometimes regrow a new set of leaves after being stripped of leaves the same season, but it is a huge stress.


  • Pine bark beetles can affect many types of coniferous trees, they take over the sap tissue and kill the tree in a short time.


  • Twolined chestnut borer  Don't let the name fool you, this borer loves oak trees, and sometimes the damage is misdiagnosed as oak wilt. Once inside, they can shut down the energy flow to the tops or ends of branches as the sap flow is compromised by infestation. 

  • White pine weevil As with any drilling insect, the damage to that part of the tree is permanent. If this happens in enough sap tissue, the sap flow stops and the tree dies. White pines, spruce, balsam, and other conifers are affected by this terror.


  • Bronze Birch Borer If you have a dead or thinning top in your birch tree, it is more than likely because of Birch Borer infestation. Once the top is dead it must be removed or it will rot back into the rest of tree until it is completely dead.


  • Spider Mites  Spider Mites can affect virtually all types of shade trees. They are very stressful to a tree since they get in close to the soft branch and leaf/needle bed area and steal nutrients. To protect itself, the tree shuts off sap flow to that spot and thus the needles and leaves shut down, causing death throughout the tree.


  • Zimmerman Moth A very disruptive bug that causes unsightly damage to spruce, white pines, jack pine, and norway red pine(and others) These cause large sores on the tree, producing "FRASS" to leak out of the tree. This pustule contains, sap, excrement, and pieces of wood. The more of these that happen, the worse the sap flow is to the top of the tree.  

  • Pine Tip Moth When eggs are laid in the emerging spring bud, the new needles grow just fine for a short time, as the insect grows, it steals all of the sap for it's own nutrition, and kills the bud. This hurts that part of the tree and the tree scabs over and the dead candle fall off, weak trees can have this happen all over the tree, killing an entire season of new needles and can cause further dieback.


  • Leaf Miner  I like to compare this bug to a person pushing a lawn mower all over the leaf. The only problem is the leaf tissue wont grow back the rest of the season. Its not aesthetically pleasing, but even worse, If enough of the leaf is damaged the photosynthesis process is lessened. 


  • Woodpeckers  If you see holes like this, the wood peckers are drilling to eat bugs, so as much as we want the bugs gone, this kind of damage is not good for your tree.


  • Sapsuckers Just as the name implies, these little birds love to get to that nutritious sap. Problem for your tree is they are killing the bark, so much so that sometimes the tree can't heal the damage and it can lose a branch or a top.

  • Squirrels Trees are loaded with nutrition, and in the late winter as squirrels run out of normal stored food, they look to the sugary layer of bark on maple trees for sustenance. If they strip the branches all the way around the trees may not heal. They may push leaves out early but after the tree "realizes" it can't maintain the sap layers above the damage and compartmentalizes the end of that branch. Porcupines will also climb and strip trees of bark, not just maples!

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