2004 Gypsy Moth Statewide Program Summary

Prepared by Kimberly Thielen Cremers, Gypsy Moth Program Coordinator, with edits and comments by Susan Burks, DNR Forest Health Specialist

General survey program

The Minnesota Department of Agriculture (MDA) was the lead agency during the 2004 gypsy moth detection survey program. Other cooperators included USDA, APHIS, PPQ; USDA, FS, MNDNR; and the Three Rivers Park District in the Twin Cities metro area. Staff in the cooperative program set 18,646 delta traps across the state, and 396 male moths were recovered. This was a 26 percent decrease from 2003, when 535 male moths were recovered.

In the fall of 2003, the STS action boundary moved into southeast Minnesota. This change did not have much impact on the management of gypsy moth in the state of Minnesota. What it does mean is that the gypsy moth front is nearing the Minnesota border and that the introduction pressure is likely to increase accordingly.

Overall, moth numbers were down substantially in the central and southeastern part of the state, making up only 107 of the total moths captured. The big surprise for the 2004 season was the record number of finds in Cook, Lake, and St. Louis County in northeast Minnesota (see map). These three counties had a total of 286 moths combined, with Cook County alone at 198 moths. With the record low temperatures throughout the months of June, July, and August (frost in parts of northeastern MN in August), it was expected that traps in northern Minnesota would also show a substantial decrease in moth numbers. That did not end up being the case. It is expected that in 2005, the STS action boundary will be expanded to include Cook and Lake Counties in northeastern Minnesota. However, for the first time since the area was trapped on an annual 1 mile base grid beginning back in 2000, there was some correlation between positive finds and delimit sites (sites with past finds), which suggests isolated introductions (which are easier to control) rather than the possibility of low density resident populations suggested by widely scattered single moth catches.

Several grid densities were utilized across the state to be consistent with past trapping protocols yet allow for a smooth transition into STS protocols and data collection. The STS action area was trapped on a 2-kilometer grid with several areas of concern receiving a higher density of traps. Areas outside the STS action area that were considered high-risk for the introduction and establishment of gypsy moth received traps on a 1500 meter grid similar density to the one trap per square mile (1/1) density that had been used in the past. Areas are 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 extending north through the city of St. Cloud, counties bordering Wisconsin in southeastern Minnesota including Fillmore and Olmsted county, and two quads inland from the shoreline of Lake Superior including the entire city of Duluth.

The remainder of the state received traps at one trap per four square miles (1/4) or 3-kilometer grid on a four-year rotation, with approximately one-third of the state receiving traps annually. The entire central half of Minnesota was trapped in 2004 including the counties of Benton, southern portion of Cass, Chisago, Crow Wing, Dodge, Douglas, Isanti, Kandiyohi, Meeker, southern portion of Mille Lacs, Morrison, Mower, Otter Tail, Pine, Rice, Stearns, Steele, Todd, and Wadena. All Municipalities within these areas received a higher trapping density of 1500 meters. In addition to the standard trapping densities, areas which had positive moths in the past received intensive trapping or delimit trapping at densities of 250 meter, 16 traps per square mile, 500 meter, or 1 kilometer to determine if a potential population exits.

Additional traps were set at state parks, mills, and nurseries within the standard trapping grid. Thirty-nine of Minnesota's 69 state parks were within the standard trapping grid and received 1-2 additional traps. Twenty-eight moths were caught in the state parks.

Mill and nursery trapping

Mills and nurseries were trapped according to risk of gypsy moth introduction. Nurseries either reporting stock sources from gypsy moth-quarantined areas, who are wholesale dealers, or who have a history of pest problems are considered high/moderate-risk, and received between two and twelve traps this year. One hundred seventy nurseries are considered high/moderate-risk. Outside the standard grid, MDA nursery inspection staff trapped five high-risk nurseries and no moths were caught.

High-risk mills throughout the standard trapping grid received two random traps. 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. There are 63 high-risk mills throughout Minnesota.

Mills that are high-volume pulp or veneer or have greater than 500 MBF annually are considered to be at moderate risk. Moderate-risk mills received two traps if they were in the 1/4 trapping grid. There are 80 moderate-risk mills throughout Minnesota.

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 on a 250-meter grid. One hundred seventy five traps were set at compliance mills. No gypsy moths were captured at these sites.

Trapping for Asian gypsy moth was conducted at the northern Minnesota seaports of Duluth (MDA). Any moths collected at the seaport or in St. Louis, Lake, and Cook Counties are sent to OTIS Laboratories for Asian gypsy moth DNA analysis. No Asian gypsy moths have been identified at this time.

USDA, FS trapping

The USDA, FS provided funding to MDA to trap all other National Forest land and Bureau of Indian Affairs land within MDA√?¬?s standard trapping grid. Since 2002, a seasonal trapper conducted √?¬?hike-in√?¬? trapping along a predetermined 1/1 grid, 1500 meter in 2004 (as opposed to using available roads) for all of the Grand Portage Reservation in Cook County. One hundred seventeen traps were set on the Grand Portage Reservation, and 22 moths were caught in 19 traps. Ten traps were set on the Fond du Lac Reservation, and no moths were trapped. Nine hundred seventy nine traps were set in Superior National Forest, and 219 moths were caught in 153 traps.

Egg mass surveys

Only one site, north of Tower and one mile south of the Boundary Waters Canoe Area (BWCA) Wilderness boundary in northern St. Louis County, warranted an egg mass survey. The survey was conducted on October 26, 2004 and two egg masses were found at the site. There is a combination of forested landownership between Superior National Forest, St. Louis County, and the City of Tower. This site is being proposed for treatment with Btk in 2005.

General treatment program

In 2004, Minnesota conducted gypsy moth eradications at six separate locations across the state. Four of the six locations were regulatory sites (nursery operations) that had received quarantine breach material during the 2003 season. All four nursery operations were under state/federal compliance agreements, which required spring treatments in 2004. The other two sites were funded by state and federal cost share dollars.

Dimilin Treatments:

All four nursery operations conducted two applications of Dimilin, spaced 7-14 days apart. The first application was conducted on April 16, 2004 and the final application was conducted on May 8, 2004. The individual nurseries paid treatment expenses. After successful treatments were conducted the compliance agreements were removed. All four sites received intensive trapping during the 2004 trapping season and three of the four nurseries had positive gypsy moth finds. Site inspections were conducted and no alternate life stages were found. No further regulatory action has been taken at this time.

Btk Treatments:

One site in the Edina area within the Twin Cities metropolitan area received two applications of Btk, spaced 7-10 days apart. This was a rather small site of less than 5 acres in size. Both applications were conducted by ground utilizing a hydraulic mist blower. This site was part of the 2002 Lake Harriet treatment delimit site and had been delimit trapped for three years, with an increase in trap density from 16 traps per square mile in 2002 to 36 traps per square mile in 2003. Twenty-two moths were caught in seven traps at this site, the largest number of finds at a single site for the 2003 season. During the egg mass survey, more than a dozen egg masses were found on two large, isolated oak trees. A USDA-FS trained tree climber assisted in removing between 30-40 egg masses from these two oak trees.

After the treatments, the site received mass trapping at 3 traps per acre and two male moths were caught at the far northeastern corner. This site will again receive intensive trapping in 2005 to determine treatment success.

Pheromone Flake Treatment:

One site in southeast Minnesota totaling 225 acres was proposed for pheromone flakes. This site has had a history of low gypsy moth finds since 2002. Moth catches increased from eight moths in one standard detection trap (1 per sq mile) in 2002 to 14 moths in five delimit traps (36 traps/sq mile) in 2003, indicating the likelihood of a reproducing population. No egg masses were located during follow-up egg mass surveys (Fall of 2002 & 2003), although this is not unusual in forested areas with low gypsy moth populations. Pheromone flakes were the preferred treatment option at this site due to location, the history of finds at the site, and the forested component.

The pheromone flake treatment was conducted on June 28 and was completed without incident. The aircraft flew into Minnesota from an airport in Boscobel, Wisconsin. The site received 15.2 grams active ingredient (disparlure) per acre. A total of 85 grams of flakes were applied.

The site received follow-up traps in 2004 to ascertain that no male moths were caught in the pheromone traps (i.e., males are sufficiently confused by the amount of pheromone used that they are unable to locate the traps). No male moths were caught in these traps. Intensive trapping will be conducted in the summer of 2005 and 2006 at a density of 250 meters. This monitoring will determine whether the project was successful and whether there is a need for further action.

Future Outlook

Although, moth catches along the North Shore were correlated to some extent with existing delimit sites, the large number of catches across a wide-area is a concern. Typically, isolated introductions that later become established produce a pattern of moth catches that increase in number over time around a focal point. The intensity of the focal point among a background of relatively few, if any moth catches, makes locating isolated populations much easier. A more or less uniform distribution of moth catches over a wide-area provides few clue as to the origin of the population. That kind of pattern suggests either a low-density resident population across the landscape or a 'moth blow'. A moth blow occurs when weather patterns pick up a large number of moths and either move them or drop them into another area. While the occurrence of moth blows has been debated, there is considerable evidence to defend the theory. For instance, early in the history of the Wisconsin infestation, trap data demonstrated two peaks in the timing of moth catches. These two peaks neatly corresponded to the timing of moth emergence in the few isolated populations within WI and to emergence in the larger MI infestation. Apparently, at least some of the WI moth catches were being blown in as adults from MI.

Along the North Shore, moth catches in 3 of the last 5 years were widely scattered across the landscape. The interim years saw few moth catches, so no clear pattern was evident (except around 1-2 delimit sites that were being closely monitored). The same pattern was seen in the early years of moth catches in Door County, WI. The question is whether the North Shore catch is s due to moth blow or a resident population. In Door County, even though moth blow was evident, there was also a resident population that dramatically increased in number in the mid 1990s. In that case, moth blow obscured the data, so the resident population wasn't evident until it had grown substantially. Could that be happening in the North Shore?

We don√?¬?t know. The current data suggests moth blow is producing the pattern of moth catches seen along the North Shore. One piece of evidence to support that theory is the moth catch pattern in the Apostle Islands. This year, moth catches along Apostle Island shorelines were extremely high, while moth catches in the interior of the islands were quite low. If the moth catches were due to a resident population, you would expect to see uniform moth catches across the entire island and not just along the shore. Moths associated with the shoreline tend to suggest the moths were moving across the water and were trapped by the first trap they came to. Given the high numbers of moths building on the mainland, moth blow makes sense to explain the patterns seen. But the STS scientists are carefully studying the data. That attention is the best part of being included in the STS action zone, because few in Minnesota have the experimental expertise to decipher these complex patterns (a plug to encourage the UMN to fill their vacant staff position in forest entomology). The end result is that as the Wisconsin infestation moves closer, we don√?¬?t know which will become infested first (if they aren't already), SE Minnesota or the North shore. Both are predicted to become infested sometime around 2007 or 2008. However, even after permanent infestations move into the state, we are likely to see many years before gypsy moth defoliation becomes an issue. So instead of panicking just yet, we ought to take the time to review the management status of those lands under our care and prioritize those at need of attention prior to gypsy moth arrival.