Forest Insect and Disease Newsletter

2012 Gypsy Moth Trapping Results

map of 2012 Minnesota Gypsy Moth trapping ResultsThe gypsy moth detection program is a cooperative effort between state and federal agencies including the Minnesota Department of Agriculture (MDA), the Minnesota Department of Natural Resources (DNR), the USDA Animal and Plant Health Inspection Service, Plant Protection and Quarantine (APHIS PPQ), USDA Forest Service (FS), and the University of Minnesota. With state regulatory authority over invasive species, MDA is the lead agency overseeing the state's gypsy moth effort.

In 2012, MDA and partners placed 17,422 traps around the state using a combination of delta and milk carton-style traps. The larger milk carton traps were used in the areas with a history of high moth captures (primarily Cook and Lake Counties), while the delta traps were used at varying grid densities elsewhere in the state. Grid densities vary based on the risk of introduction and relative distance to the national Slow-The-Spread (STS) action boundaries.

The traps caught 10,445 moths, almost all of which were in the northeastern-most counties (Map 1). That total is down from the record 27,870 moths caught in 2009, but up from the count in 2011(Graph 1). The overall trend suggests that low density populations are beginning to build in the Arrowhead region. As a result of the pattern of trap captures and alternate life stages found in Cook County, the STS "Action Zone"(Map 2) will move slightly westward for the next trapping season. The Action Zone is one where more traps are deployed to detect lower numbers of gypsy moths in an effort to eliminate low-density populations.

Additional trapping was done to monitor the efficacy of the treatments carried out in 2011. The treatment block of most concern was in Grant Township (Washington County), where a large number of alternative life stages (egg masses, pupal and larval skins) were found. Treatment success was assessed through additional trapping in the area.

There were three blocks of land treated in 2012 based on 2011 trap captures (Map 4). All three blocks were treated with pheromone flakes designed to disrupt gypsy moth mating (roughly .5 cup of flakes per acre). These areas will be heavily trapped next year to monitor treatment success.

Based on this year's trapping results, four blocks of mating disruption treatment are being recommended for 2013, all in St Louis County (Map 5). Because of the westward shift of the STS action zone, none of the areas of concern in Cook and Lake Counties will be treated; those areas will be trapped to monitor population levels.

Note: Gypsy moth graph and maps courtesy of MDA, except in Map 3.