What are Japanese Beetles and why are they a threat to my landscape?
Adult Japanese Beetle
Japanese beetles are a serious invasive insect pest of both turf and ornamental plants. Introduced to the U.S. from Japan in 1916, Japanese beetles have no natural enemies in Minnesota to naturally control the population. Beetle grubs are white and ‘C’ shaped, about 3/4 to 1 inch in length while adult beetles are approximately 3/8 -1/2 inch in length with a metallic green head with dark tan wings. Please note that there are other grubs and adult beetles that look similar but may not cause the type of damage that Japanese beetles cause. Therefore it is important to contact an ISA Certified Arborist for correct identification.
Both larvae and adult Japanese beetles cause damage. The larva, or grubs, damage turf by consuming grass roots creating dry patches that easily lift up. Look in nearby healthy turf for grubs just under the soil. Granular insecticide applications followed by watering in mid May to early June can provide good control for grubs.
Skeletonized leaf from Japanese beetle feeding
Adult Japanese beetles cause significant damage to foliage of many types of trees, shrubs and plants. Trees susceptible include: linden, paper birch, crabapples, and elm. Shrubs and perennials susceptible include: grapes, roses and hollyhock. Adult beetles feed beginning in early July until late August creating a ‘skeleton-like’ appearance on the leaves with only leaf veins remaining.
Here’s what we can do
Shadywood Tree Experts can help maintain your trees with the use of insecticide applications and annual fertilization. When you sign up for plant health care from Shadywood, we administer the recommended protocols for disease prevention control to keep your trees healthy. With each visit, our arborists assess trees for overall health.
Linden tree showing symptoms of Japanese beetle damage at the top of leaf canopy
Additional things you can do to maintain the health of your tree
Water trees regularly using a hose or lawn sprinkler for at least an hour every one to two weeks if there has not been adequate rainfall. Mulch root systems when possible, using natural wood chips to protect the trunk, condition and improve the soil, and to conserve soil moisture. If you see anything that doesn’t look right, have your trees inspected by one of Shadywood Tree Experts International Society of Arboriculture Certified Arborists.