Gypsy moth treatment proposed for area in Richfield, Armatage

Photo courtesy Minnesota Department of Agriculture

The Minnesota Department of Agriculture is looking to spray an insecticide in the northwest corner of Richfield and a portion of Armatage this spring to prevent a gypsy-moth infestation.

The department is proposing to spray the 329-acre area between West 61st Street, West 67th Street, Washburn Avenue South and Logan Avenue South with Bacillus thuringiensis, a naturally occurring bacteria commonly found in food and soil, according to the Minnesota Department of Health.

The bacteria has been used for over 30 years to control insects and is considered safe for humans, according to MDH. Even so, the department recommends that people may want to stay indoors during application unless it is essential and for at least 30 minutes after to allow the droplets to settle.

It also recommends that people wait until the treatment has dried before touching grass or shrubs and wash off residue on playground equipment, sandboxes, benches or lawn chairs.

The MDA typically treats for gypsy moth in May, according to Pest Mitigation and Regulatory Response Unit Supervisor Kimberly Thielen Cremers, but that could be pushed into late April if the weather continues to stay warm.

The department applies the treatment at sunrise or shortly after, delivering the spray either by plane or helicopter. The aircraft flies about 50 feet above the treetops and is loud, according to the department. It takes about 30 minutes to treat a 640-acre block with a plane or two hours by helicopter. Treatments occur twice, about a week apart.

Gypsy moths are one of North America’s most destructive tree pests, according to MDA, and have defoliated entire forests and caused millions of dollars in damage. They don’t necessarily kill trees, Thielen Cremers said, but they stress them enough so they become more susceptible to other insects and diseases.

As thousands of caterpillars feed, there is an audible sound of caterpillar droppings falling to the ground, according to MDA. The caterpillars shed their bristly skin four or five times as they grow, and the bristles may become airborne and irritate human eyes, skin and respiratory systems. MDA says many people develop a rash if they come into contact with the bristles.

MDA notes that treatment at high infestation levels is more costly than the current low level of infestation and is typically funded in part or completely at the local level, including by individual property owners. It says that when gypsy moths become generally established, counties go into quarantine status, which means that no outdoor household articles can be moved to non-quarantines areas without proof they have been inspected and found free of gypsy moths.

Thielen Cremers said the gypsy moths were brought to the Minneapolis/Richfield area through human activity. MDA detected 12 male moths in a trap this past summer and then found multiple egg masses on sight, she said.

“We were just very fortunate to find it very early,” she said.

MDA implemented a quarantine in November, restricting the movement of trees and woody material, including firewood, out of the area until June 15. The quarantine has also required residents to self-inspect any equipment, household items or vehicles that were sitting outside in the quarantined area during the summer months when gypsy moths are active and that were being moved out of the quarantined area.

The department has an annual-trapping program to determine where treatments may take place. It’s also proposed treatments for this spring in Pine and Winona counties.

Thielen Cremers recommended that people stay up to date on treatment information by calling MDA’s “Arrest the Pest” hotline at 1-888-545-6684 or by signing up for email updates. The email update signup can be found at under the “Gypsy Moth Treatments” tab midway down the page.

She said she believes the department would be able to eradicate gypsy moths from the site and keep them out for many years to come.

MDA is going to hold a community open house to answer questions about the treatment. That will be from 4-6:30 p.m. March 1 at Sheridan Hills Elementary (6400 Sheridan Ave. S.).