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MDA to set 20,000 traps to survey for spongy moth

The Minnesota Department of Agriculture (MDA) will set approximately 20,000 traps this year looking for spongy moth (Lymantria dispar), formally known as gypsy moth.

The traps will be set throughout the eastern half of the state and in far northwestern Minnesota as part of a “western rotation.”

This work is part of the MDA’s annual trapping survey program and is designed to protect Minnesota’s forests and urban areas from new infestations of spongy moth by detecting potential problem areas for future treatments. While the goal of the program is not to trap every spongy moth, trapping is vital to early detection and slowing the spread. In 2022, a record number 101,763 spongy moths were trapped, making it even more important that efficient trapping efforts continue.

Survey staff have begun setting traps and will continue through July. Traps will remain in the field through August in the southern region of the state and through October in the northern region. The “delta” traps are small, triangle-shaped and made of cardboard. Bigger “milk carton” shaped traps will be set in select areas of Lake, Cook, and St. Louis counties to accommodate potentially higher numbers of moths. All the traps contain a pheromone to lure in male spongy moths if they are present.

The traps are placed mainly on trees in a grid pattern at a specific distance from each other. The grid allows for the traps to efficiently trap as many male moths as possible. To be successful, it is important to maintain the trapping grid. Citizens are asked not to disturb the traps and to call MDA’s Report a Pest line at 888-545-MOTH (6684) or email if they would like traps removed from their property.

Community member cooperation in the trapping survey program is vital to its success. In addition, this year the MDA is asking the public to be extra vigilant on spotting potential infestations and reporting potential spongy moth sightings via the Report a Pest online service or by emailing

Spongy moth caterpillars are a problem because they eat the leaves of over 300 types of trees and shrubs, favoring oak, poplar, birch, and willow. Severe, repeated infestations can kill trees, especially when the trees are already stressed by drought or disease.

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