Tree Pests

Pest Prevention and Treatment

Emerald Ash Borer

These invasive insects have killed millions of Ash trees. They spread by the adult female laying her eggs in the bark of a healthy Ash tree. Once the eggs hatch the larvae then feed on the tree until adulthood, killing the tree in the process, and the cycle then continues with the new generation.

Preventative measures for EAB would include pruning your Ash trees ONLY during the insect's dormant period (October 1st-April 30th). Removing dead or infested trees promptly and quarantining the wood after removal, by keeping the infected wood in the infected area, to protect healthy trees is vital. If applicable, insecticide is an option for treating exposed and infested trees, but it can be spendy and might not save your tree. 


Spongy Moth

This species of moth is invasive and is very opportunistic as it has been known to feed on over 300 different tree species. The caterpillar phase is the more aggressive phase and can feed to the point of death for plants. These moths are called hitchhikers because the spread is mostly enabled by humans transferring their egg masses accidentally. Their eggs can be laid on anything from plants to lawn chairs. 

To prevent the spread of the moths, they are considered a quarantined species. this means that any items or wood that have been in contact (even just by location) or infected by the moth need to stay in their original spot. This would include even firewood. So be sure to check if the area you are in or visiting is considered an exposed area and check items you transfer diligently for their egg mass pictured in the infographic. 

Japanese Beetles

These beetles are invasive and have been in Minnesota since '68. They are also opportunistic feeding on over 300 Minesota plant species. Beetle damaged leaves create an odor that attracts more beetles to the site, who can fly several miles from site to site. Japanese Beetles don't necessarily kill plants unless it is an unhealthy or young plant, then the infestation could be deadly. 

Prevention matters for these beetles don't have to include pesticides. You can spray them off your infected plant with a hose, which is effective with consistency. You can also physically remove them by grabbing them from leaves and then dropping them into soapy water. Pesticide should be the last option because of the harm it can cause birds and pollinators.