Here is a full list of these popular types of trees in MN, including information about how to tell them apart, how to care for them, and what diseases they might get. This guide will help you learn more about the southeast MN/southwest WI trees, whether you’re a budding ISA Certified Arborist or just a curious local.

Tree Diseases

In southeast MN and southwest WI, numerous diseases afflict trees, such as Apple Scab, Needlecast, Dutch Elm Disease, Tar Spot, Anthracnose, and Oak Wilt.:

 

  • Apple scab: A fungal infection of apple and crab trees, this disease gives trees brown spots on leaves and fruits. Treatment includes an anti-fungal to apply to leaves as well as removing dead or dying leaves from the root of the tree.
  • Anthracnose: The fungal disease causes browning, curling, and leaf drop in oaks, ashes, and maple trees. Treatment includes preventative fungicide applications and removal of infected leaves. 
  • Dutch elm disease: When Minnesota’s native elms get this fungal disease, their leaves will yellow and wilt. If caught early, treatment can include pruning of affecting limbs and use of fungicides. 

  • Oak wilt: A non-native fungus can infect oak species by invading the water-conducting vessels, causing leaves to wilt. Treatment includes root cutting, fungicides, and removing infected trees.
     
  • Diplodia tip blight: This fungal disease attacks weakened pines and kill the needles at the tip of the branches. Treatment includes pruning diseased limbs, removal of diseased cones and needles, and application of chemical fungicides. 

  • Dothistroma needle blight: This fungal disease causes browning and loss of needles in pines. Treatment includes removal of infected leaves, mulching, and preventative fungicide.

  • Rhizosphaera needle cast: This fungal infection affects spruce trees, causing their needles to have back spots of fungus spores that can cause branches to die. Treatment includes extra watering, mulching, and a fungicide spray.

  • Cankers: These localized dead areas of spruce, maple, and honeylocust trees require pruning to minimize the spread of the disease. 

  • Armillaria root rot: When fungus infects deciduous and coniferous trees, the roots can rot. Treatment includes the removal of infected trees and trenching. 

 

Tree Pest

The southeast MN/southwest WI region is affected by a variety of pests that can damage trees. Some of the most common tree pests and diseases in Minnesota include:

 

  • Eastern larch beetle: This beetle infests tamarack that are stressed, eventually attacking healthy trees.

  • Emerald ash borer: This destructive insect attacks ash trees and can be prevented by insecticides

  • Forest tent caterpillar: These insects damage trees by feeding on trees and slowing their growth rate. 

  • Spongy moth: These moths defoliate trees, leaving them vulnerable to diseases and other pests.
  • Pine bark beetles: These are the most damaging bark beetles that attack pines and typically those that have been freshly cut.

  • Twolined chestnut borer: These insects attack weakened oaks, killing them in two to three years. 

  • White pine weevil: The most destructive insect of white pines, these insects cause trees to wilt, droop, and die.