Gypsy moth update

Taken from MDA Final Report By Kimberly Thielen-Cremers

map of 2003 gypsy moth totals by county

General survey program

The Minnesota Department of Agriculture (MDA) was the lead agency during the 2003 gypsy moth detection survey program. Other cooperators included USDA, APHIS, PPQ; USDA, FS; DNR and the Three Rivers Park District in the Twin Cities metro area. Staff in the cooperative program set approximately 17,790 delta traps across the state, and 535 male moths were recovered. See map. This was a 453 percent increase from 2002, when 118 male moths were recovered.

Traps were set at one trap per square mile (1/1) in areas considered high-risk for the introduction and establishment of gypsy moth due to human activity levels, preferred habitat for gypsy moth, and the advancing gypsy moth front from Wisconsin. Areas designated high-risk included the seven-county Twin Cities metro area, counties bordering Wisconsin in central and southeastern Minnesota, and along the shore of Lake Superior including the entire city of Duluth. The remainder of the state receives traps at one trap per four square miles (1/4) on a four-year rotation, with approximately one-third of the state receiving traps in any one year. The entire eastern half of Minnesota was trapped in 2003.

As in 2002, a seasonal trapper conducted hike-in trapping along a predetermined 1/1 grid (as opposed to using available roads) for all of the Grand Portage Reservation. Two hundred forty traps were set on the Grand Portage Reservation, and six moths were caught in five traps. Forty-nine traps were set on the Fond du Lac Reservation, and no moths were trapped. Nine hundred fifty traps were set in Superior National Forest, and three moths were caught in three traps.

Moth counts

Type of trap


Standard detection (1 trap/sq mi)


Standard detection (1 trap/4 sq mi)


Delimit (16-36 traps/sq mi)




Nursery delimit




State Park



Nursery and mill trapping

Nurseries either reporting stock sources from gypsy moth-quarantined areas or who are wholesale dealers are considered high-risk. Outside the standard detection grid, 34 high-risk nurseries were trapped and one moth was found.

Logging mills are considered high-risk if it is known or likely that they have out-of-state sources or if they are within 60 miles of Wisconsin counties trapping fifty or more moths. Outside the standard detection grid, 16 high risk mills were trapped and no gypsy moths were recovered at these mills. Three mills are under federal Compliance Agreements for gypsy moth. A Compliance Agreement is designed to decrease the risk of gypsy moth establishment and allows mills to transport logs from gypsy moth-quarantined areas for milling or pulpwood. Mills under compliance are trapped at 36 traps per square mile for one square mile. Sappi, Blandin and International Paper were trapped and no gypsy moths were found.

Egg mass surveys

Three egg mass surveys were conducted in the fall in response to relatively high trap catches at the sites. Two sites were within the Twin Cities metropolitan area (Edina and Hugo) and one was in rural southeastern Minnesota (Rollingstone). The Minneapolis site was part of the 2002 Lake Harriet treatment delimit area. Twenty-two moths were caught in seven traps at this site, the largest number of finds at a single site for the 2003. During the egg mass survey, more than a dozen egg masses were found on two large, isolated oak trees. This site will receive a treatment in the spring of 2004. No egg masses were found during the two other surveys.

Regulatory incidents and quarantine breaches

In early July, MDA was notified that Colorado blue spruce shipped from another Midwestern state to an Iowa nursery was infested with gypsy moth larvae and egg masses. One Minnesota nursery had received stock and when a site inspection was conducted, three spent egg masses were discovered. A Stop Sale Order was immediately issued until further inspection could be conducted, but was suspended the next day when no other life stages were located.

In late July, multiple males were caught in survey traps at four nurseries: two in the Minneapolis-Saint Paul metropolitan area (Blaine and South St. Paul) and two within 70 miles of the Twin Cities (Hanover and St.Cloud). All four businesses were immediately issued Stop Sale Orders. Inspections at the four sites revealed multiple gypsy moth life stages, and as a result, each of the nurseries entered into formal compliance agreements with MDA and USDA, APHIS. One provision of the compliance agreements was that the nurseries must treat for gypsy moth in the spring of 2004, and all conifer material must be held off-sale until treatments have been completed. Two of the businesses were unable to over-winter their conifers so those nurseries elected to burn potentially infested material. Further investigation into the source of the infested material at the four Minnesota nurseries revealed three separate nursery quarantine breaches from three different states within the federal gypsy moth quarantine. All material arrived in Minnesota with the proper gypsy moth certification paperwork.

Two of the Minnesota nurseries received infested stock several months before the quarantine breach was discovered, allowing for possible cross-contamination of other stock on site. The majority of the potentially infested stock had already been sold to other nursery dealers, landscape contractors, or homeowners across the state by the time MDA learned of the breach. Follow-up surveys are being conducted across Minnesota to determine if stock sold to secondary customers was indeed infested. See map.

map of 2003 gypsy moth quarantine