Two invasive insects new to Minnesota were reported to the Minnesota Department of Agriculture’s (MDA) Report a Pest service in August. Both insects were reported by two separate vigilant homeowners and were later confirmed as invasive insects: The elm seed bug (Arocatus melanocephalus) and Asiatic garden beetle (Maladera formosae).
Elm Seed Bug
The elm seed bug is an invasive insect that has piercing sucking mouth parts and primarily feeds on elm seeds but can also feed on linden and oak. The elm seed bug is mostly considered a nuisance pest like the box elder bug, as they can enter homes in large numbers. Box elder bugs are active in late summer and fall, but the elm seed bug is active in mid-June.
Native to Europe, elm seed bug was first confirmed in the United Stated in 2012. It is established in several western states, such as Oregon, Washington, and Utah.
Adult elm seed bugs are about 1/3 inch long; they’re a dark rusty-red and black color. The underside of the insect is red. On the back behind the head, there is an upside-down black triangle set inside two rusty-red triangles. Next to the edges of the wings where the abdomen is exposed are alternating white and rusty red-black patches.
Best management practices include sealing cracks and crevices on the exterior of buildings so the insects cannot enter and vacuuming up insects that make it inside. To limit entry into structures, there are certain insecticides that can be applied as a barrier treatment.
Asiatic Garden Beetle
The Asiatic garden beetle is an invasive insect that feeds on over 100 hosts, including fruit, vegetables, perennials, and annuals. Grubs prefer roots of ornamentals and garden plants. Preferred hosts include butterfly bush, rose, dahlia, aster, and chrysanthemum. Adults feed on the leaves and flowers of their host plants. Heavy infestations can lead to complete defoliation except for the leaf midribs.
Native to Japan and China, this beetle was first found in the United States in New Jersey in 1922. It is established in New England and a few Midwestern states, including Illinois and Indiana.
Asiatic garden beetles are about 3/8 inch long, are chestnut brown, and may have a slight iridescent sheen. The abdomen protrudes slightly from the wing covers. Adults emerge at night and fly actively when temperatures are above 70 degrees Fahrenheit. They are related to Japanese beetles but differ in that Japanese beetles fly and feed during the day and Asiatic garden beetles feed at night.
Since both elm seed bug and Asiatic garden beetle are newly discovered in Minnesota, the MDA would like to better understand where these insects may be in the state. Residents can report suspected sightings of both insects to the MDA’s Report a Pest line or call 1-888-545-6684. Please include clear photos when submitting a report online.
Brittany Raveill, MDA Communications