Forest Insect and Disease Newsletter

Emerald Ash Borer and Gypsy moth update

Forward - The MN Department of Agriculture (MDA) is the lead agency responsible for the detection and management of regulated pests, which includes among others, the emerald ash borer (EAB) and the gypsy moth (GM). Except on our own lands, the DNR holds a support role in all planning and implementation efforts involving regulated pests impacting Minnesota's natural resources.

This year, the DNR agreed to take a lead role in incident command when needed to respond to newly discovered EAB infestations in rural Minnesota. The extent of our involvement (except on our own lands) is at the discretion of MDA, the entity with the ultimate responsibility to manage regulated pests.

 

Emerald Ash Borer

image: EAB highlight of quartine boundariesMetro Area History (map external link):

  • May '09 found in a residential area of St Paul. Likely source is solid wood packing material associated with the adjacent rail yard. Likely began around 2005.
  • February '10 found in Prospect Park in Minneapolis, likely due to natural spread.
  • Oct '10 found along East River Rd in Minneapolis, likely due to natural spread.
  • March '11 found along West River Rd in Minneapolis, likely due to natural spread.
  • July '11 found in a residential area of Shoreview on the Anoka/Ramsey County border. Source is unknown (too far away to be natural spread). Likely began around 2008.
  • Sept '11 found in St Paul, near the intersection of Summit & Dale. Possibly due to natural spread or the movement of firewood for home use. Likely began around 2007. Southeast Area History (see map 2):
  • August '08 found in Milwaukee in eastern WI.
  • April '09 found in Victory, WI near the WI/MN/IA border. Likely source is firewood used for home heating.
  • April '10 found on US Fish &Wildlife Service (F&WS) island in Houston County, likely due to natural spread across the river. Likely began around 2007.
  • Sept '11 found in Winona County near intersection of I-90 & CR12, and in Great River Bluffs SP. Likely began around 2005.

image: Map of EAB quarantine boundaries in southern MN Southeast Area History (map external link):

  • August '08 found in Milwaukee in eastern WI.
  • April '09 found in Victory, WI near the WI/MN/IA border. Likely source is firewood used for home heating.
  • April '10 found on US Fish &Wildlife Service (F&WS) island in Houston County, likely due to natural spread across the river. Likely began around 2007.
  • Sept 11 found in Winona County near intersection of I-90 & CR12, and in Great River Bluffs SP. Likely began around 2005.

EAB Pest Management

Metro Area:

  • Hennepin and Ramsey Counties were quarantined in 2009. Quarantines monitor and regulate movement of ash and ash products (including mulch), and hardwood firewood out of the quarantined boundaries.
  • MDA has contacted all businesses related to the movement or disposal of wood within those counties. Many have established compliance agreements so their products can be safely shipped out of the area.
  • The cities of Minneapolis and St Paul are actively looking for and removing publicly owned ash trees known to be infested, except along MS River bluff where steep terrain hinders sanitation.
  • St Paul and Shoreview are requiring the removal of privately owned ash trees known to be infested. To date, Minneapolis has been reluctant to enforce their nuisance ordinance on private lands due to a lack of confidence in their ability to correctly identify infested trees.
  • Federal funds have supported much of the sanitation work accomplished to date.
  • Minneapolis and St Paul have been pre-emptively removing and replacing some ash trees along their boulevards to increase the diversity of their urban forests.
  • A number of other communities have adjusted their maintenance schedules and are removing and replacing ash at a faster rate than before the discovery of EAB.
  • State funds have supported much of these urban forest diversification efforts.

Southeast Area:

  • Houston County quarantine was quarantined in 2010 and Winona County was quarantined in 2011.
  • Again, MDA has contacted all businesses related to the movement or disposal of wood within those counties. A few compliance agreements were developed as a result of those contacts.
  • MNDOT and DNR Parks are actively removing ash trees known to be infested. Some of the smaller infested trees are being taken to the quarantine facility at the UMN to support research into the cold tolerance of EAB and the biocontrol agents. The rest are being chipped and utilized on-site.
  • MNDOT is also removing uninfested ash in several plantings near the I90 infestation to make use of available labor (utilizing plow drivers currently idle).
  • The F&WS is not removing infested trees on the island near Victory because of difficult access.
  • WI is not enforcing sanitation of trees known to be infested in Victory, WI (mostly private lands).

EAB Survey and Monitoring

  • image: Aerial surveys over great river bluff state park (DOTs represent photo centroids) Every year, MDA and USDA APHIS put up green or purple prism survey traps on a grid basis in the highest risk areas of the state and other locations as warranted. These are checked once during the season and again when they are taken down in the fall.
  • Winter surveys consist of visual inspections of ash trees in and around known infestations. Indication of wood pecker feeding is the most easily recognized sign of infestation. Winter surveys are carried out by a combination of state and city staff.
  • The DNR took and is now interpreting aerial photography over the Winona County infestations & positive trap sites. Purpose is to detect new infestations that may better explain the pattern of positive trap captures in the area.
  • Reports of suspect EAB are monitored through the MDA Arrest-A-Pest Hotline and the network of volunteer First Detectors.
  • First Detectors are trained through a series of workshops put on through a collaboration of the UMN, MDA and DNR. There are now over 382 in the state, covering 64 counties.

EAB Biocontrol

  • image: Aerial surveys over great river bluff state park (DOTs represent photo centroids) Two larval parasites & one egg parasite (all non-stinging wasps) have been released at all currently known infestations. All three species are specific to EAB, and not likely to attach native wood borers.
  • 300 trees not known to be infested within 2 miles of the core infestation in MPLS & St Paul have been characterized. Two branches from each tree will be removed each yr for 3 yrs to monitor the rate of spread for EAB & biocontrol agents.
  • This branch sampling method was recently developed in Canada to survey for EAB. The advantage is that its 75% effective in detecting EAB in trees that have no other sign of infestation. This is the first time the methods have been used in MN, but are already showing promise – the 1st branches cut and peeled this fall were found to be infested – a new find for that area. This may be an effective way for Park mgrs to monitor EAB in their campgrounds.

EAB Implications

  • On its own EAB moves very slowly. So sanitation is effective at removing portions of the population and slowing its rate of spread.
  • EAB is very difficult to detect. So infestations may be present long before being discovered.
  • Federal funding is drying up because eradication efforts have failed elsewhere in the country and survey methods are currently inadequate to effectively monitor EAB populations.
  • Research has indicated that EAB will kill 99% of all ash within the state. Natural ash regeneration is unlikely. Where ash is the primary regulator of site hydrology, stands may convert to shrub or peat lands.
  • Research has shown that removing healthy trees within an infestation may speed the rate of spread, because adult beetles are forced to fly further in search of food.
  • On the other hand, stand thinning (to reduce the proportion of ash) where feasible to increase stand diversity is advised before the stand becomes infested, as a means of sustaining forest cover.
  • Once dead, ash trees become very brittle. Michigan has seen significant costs associated with fallen trees knocking down power lines. Addressing public liability on DNR lands will be needed.

Gypsy moth update

image: Aerial surveys over great river bluff state park (DOTs represent photo centroids)

Metro Area History

  • Small, isolated gypsy moth infestations have been discovered and successfully eradicated since the 1970's.
  • There are no known permanently established infestations and the area is well outside the action zone for the national Slow-The-Spread (STS) program.
  • Life stages (egg masses or pupae) found in three areas (Minnetonka, Coon Rapids & Grant) in 2010 resulted in treatments carried out in 2011. The biological insecticide, Bacillus thuringiensis kurstaki (Btk) was used at all three sites. Survey results since indicate treatments were successful.

Southern Area History

  • Small, isolated gypsy moth infestations have been discovered and successfully treated since the 1990's.
  • There are no known infestations established in the area.
  • However, Houston and Winona Counties are within the STS action zone, so management strategies vary from those of the metro area. Instead of local eradication, the goal is population suppression to slow the rate of spread into Minnesota. Disparlure (the chemical equivalent of female gypsy moth pheromone) is used to mask her presence and disrupt mating (male moths can't find them).
  • Moth capture rates have been falling over the last several years, with no treatments needed.

North Shore History

image: Aerial surveys over great river bluff state park (DOTs represent photo centroids)

  • Cook, Lake and St Louis counties are in the STS action zone and have been seeing fluctuating peaks of moth captures.
  • Mating disruption treatments over the last eight years have been successful in suppressing local populations.
  • However, the number of moths captured has remained relatively high over the last seven or eight years, accounting for over half of the annual survey results.
  • 2008 saw a large increase in the number of moths caught, apparently due to weather events that carried moths and perhaps larvae across the lake from WI and MI. Blown moths confuse survey results and make it difficult to map resident infestations. Blown moth (all males) also increase mating success and potential population growth.
  • In 2010, larvae were found at a site in Duluth, and eggmasses and pupae were found near Finland, which suggests reproducing populations exist in those areas.
  • The Duluth area was treated with a combination of Btk and mating disruption, while the northern areas were treated with mating disruption. No additional life stages were found in 2011.

Gypsy Moth Survey and Monitoring

  • image: Aerial surveys over great river bluff state park (DOTs represent photo centroids) Survey traps are placed on grids using protocols standardized across the entire national STS program. Grid densities decrease as an area approaches the generally infested area (currently mid-Wisconsin where gypsy moth quarantines denote the generally infested area).
  • Survey results are posted on-line and analyzed through the national STS program. A sophisticated algorithm identifies potential infestations and recommends management strategies: either treatment (chemical application) or delimiting (mass trapping).
  • The STS program itself is managed by a not-for-profit foundation made up states along the leading edge of gypsy moth infestation. They decide how available federal funds will be distributed along the action zone to address the recommended management tactics.

Gypsy Moth Biocontrol

  • There are a number of biocontrol agents that help regulate gypsy moth populations in the generally infested areas. These include several introduced insects and a native virus. Native rodents also play a part, although their impact is not enough to control gypsy moth outbreaks.
  • The insects and the virus spread naturally as the gypsy moth spreads into a new area. Introducing these agents ahead of infestation is not effective and introduction behind the infestation is not necessary.
  • None of these agents are effective at controlling low density gypsy moth infestations.
  • One biocontrol agent, the fungus Entomophaga maimaiga, helps regulate gypsy moth populations in generally infested areas AND along the leading edge of infestation where population numbers are low. Because of long-lived resting spores that survive in soil for long periods, introducing the fungus ahead of infestation is feasible.
  • MDA has released the fungal resting spores at several sites along the North Shore. Because gypsy moth life stages are rare, monitoring consists of collecting and lab testing soil to verify viable spores.

Gypsy Moth Implications

  • STS program success in monitoring gypsy moth populations and slowing the rate of spread, and the structure of collaborative decision making has resulted in strong support through the USFS, with federal funds going directly to regulatory agencies in participating states.
  • However the last two years, funding levels have decreased, resulting in fewer traps being placed than past years and more suggested treatment sites being delimited instead.
  • Since 2008, the STS action zone has crept westward a bit, being centered now in St Louis County. As the action zone has moved westward and funding levels have decreased, treatments have focused on the western edge of the action zone. Reducing populations to the east toward the lake and northward toward the BWCA, where treatments are limited, have been given a lower priority.
  • While not an immediate concern, the shift in treatments westward suggests that program administrators may need to consider the possibility of quarantines in Cook and Lake Counties over the next few years.
  • Even though gypsy moths have a very wide host range, their feeding does not kill trees outright. It takes multiple years of defoliation or a combination of defoliation and environmental conditions to kill trees. As a result, gypsy moths will never produce the kind of tree mortality expected with the emerald ash borer.
  • However, the first outbreak of gypsy moth (not expected for a number of years) will be long and nasty and likely to generate a loud public reaction. Outbreaks after that will be cyclic, much like the forest tent caterpillar.
  • Mitigating long term impacts is possible through stand improvement (increase vigor) and diversification (increase resilient).