Although federal and state quarantines have likely helped slow the spread of emerald ash borer (EAB; Agrilus planipennis) nationally and locally, EAB continues to spread in Minnesota where more than a billion green, black, and white ash trees are threatened including about 2.65 million trees that have been planted in municipalities across the state. As a consequence of the continuing spread of EAB in the state, On March 20 and April 2, 2020, the Minnesota Department of Agriculture (MDA) announced the discovery of new EAB infestations in Rice County and Mower County, respectfully, and has subsequently declared county-wide emergency quarantines for these two southeastern Minnesota counties. These are the first new EAB infestations to be confirmed in Minnesota this year, and the most recent finds since Brown County and Steele County were quarantined in September of last year (2019), and increases the number of quarantined counties in the state to twenty-three.
The new EAB infestation in Rice County was detected by a public works employee who noticed an ash tree with EAB symptoms on private property in the city of Faribault while the new infestation in Mower County was discovered by an MDA employee who noticed several ash trees that were exhibiting EAB symptoms along Highway 63 north of Racine, Minnesota. In both cases, samples of live larvae were collected for formal identification. As a result of these new finds, the number of counties that are quarantined for EAB in Minnesota as increased from 19 to 21. Both of these new infestations are located in counties that are adjacent to previously infested and quarantined counties and whether they are the result of human-mediated transport or movement of the insect moving to new areas on its own is unknown.
The MDA encourages residents to check their ash trees for emerald ash borer by watching for woodpecker activity and damage that might indicate the presence of EAB larvae under the bark and by checking for cracks in the bark that may be caused by the tunneling of EAB larvae and may reveal the distinctive, S-shaped, larval tunnels under the bark. A video recently developed by University of Minnesota Extension entitled How to Look for Emerald Ash Borer Now may also help property owners assess whether their ash trees are infested with emerald ash borer and learn how to protect and manage ash trees in their landscapes that are threatened by this devastating pest. The video is a good University of Minnesota resource that arborists and garden center personnel can recommend to customers who are concerned about EAB and the health of their ash trees. When an EAB infestation is suspected, homeowners are encouraged to contact a tree care professional or their city forester. Of course, nursery and landscape professionals should also be on the lookout for signs and symptoms of EAB and both homeowners and green industry professionals should report suspected infestations to the MDA using the Arrest the Pest reporting system at 1-888-545-6684 or email@example.com.
In an attempt to prevent the spread of EAB to new areas and protect Minnesota’s ash trees, state and federal quarantines currently regulate the movement of all life stages of the emerald ash borer insect and the intra- and interstate movement of ash wood and wood products from quarantined areas including all hardwood firewood, ash nursery stock, and green lumber, wood waste, compost, and woodchips derived from ash species (Fraxinus spp.). It is critical that these quarantine restrictions be followed if the continued, human-mediated, spread of EAB to new locations is to be prevented.
It is expected that the Minnesota Department of Agriculture (MDA) will be hosting open houses for residents and tree care professionals to discuss the discoveries of EAB in Rice County and Mower County to provide information about the management of EAB and gather input on the department’s plan to add these counties to the state’s formal quarantine for EAB. In addition, the MDA is currently accepting oral and written comments on the existing emergency quarantines and the proposed implementation of state formal quarantines in these counties. In both cases, comments may be submitted by contacting Kimberly Thielen Cremers at the Minnesota Department of Agriculture; 625 Robert Street North, St. Paul, MN 55155; Kimberly.TCremers@state.mn.us, 651-201-6329 (phone), 651-201-6108 (Fax). Comments will be excepted for Rice County until April 30, 2020, and for Mower County until May 22, 2020.
With the goals of reducing the spread of emerald ash borer in Minnesota, managing the impacts of EAB on the state, and working toward healthier and more resilient forest communities across the state, the Minnesota Environmental Quality Board (EQB; composed of nine state agency heads and eight citizen representatives) and the Emerald Ash Borer Interagency Team have prepared a state agency report that defines the EAB threat and provides recommendations for achieving these important goals. The 2019 Emerald Ash Borer Report is described as a “call to action” and includes a variety of recommended actions for managing community forests and forested lands organized under four primary recommendations as follows:
- Slow the spread – Slowing the spread of EAB to prolong the beneﬁts that ash trees provide and spread the management costs over time
- Support communities – Providing counties, cities, townships, and tribal communities with technical and ﬁnancial assistance for tree inventories, management plans, and implementation strategies to reduce costs, slow the spread, and help maintain the ability to manage other community needs.
- Manage ash wood material – Development of a plan to promote the highest and best use of ash wood material and keep it from entering the waste stream.
- Lead, engage and collaborate – Promotion of a statewide, collaborative effort to address all aspects of EAB management as EAB spreads.
Remember that the emerald ash borer flight season in Minnesota begins on May 1 and continues until September 30. During this time, EAB larvae will complete their development by going through the pupal stage and metamorphosizing into adult beetles which then emerge from infested trees and fly around in search of food, mates, and new host trees. In general, the development of emerald ash borers, and other insects and biological processes, from eggs to adults is governed by temperature and only occurs when temperatures are warm enough for development to continue and can be estimated using degree days (a measurement of heat units above a base temperature accumulated over time) and can be valuable information for the management of insect pests. For EAB, the base temperature is 50° F (10° C) and it has been determined that the degree day threshold for the emergence of adults is 450 degree days with peak adult activity expected between 900 and 1100 degree days. Current base 50° F degree day accumulations for Minnesota are available using the US Degree-Day Mapping Calculator. As of April 3, 2020, degree day accumulations for Minnesota were between zero and about 20 degree days depending on location within the state with the highest number of degree days having been accumulated in the Wilmar area in west central Minnesota.
Finally, it has been well-documented that the movement of infested ash firewood is a primary pathway for the spread of EAB to new areas and firewood may not be moved from quarantined areas to non-quarantined areas unless it is certified by the Minnesota Department of Agriculture (MDA). Better yet, firewood should not be moved around the state or even within an infested county. In Minnesota, firewood may only be moved outside areas quarantined for EAB if it has been heat-treated to state standards and certified by the MDA under a compliance agreement.
With the entire state of Wisconsin under quarantine, firewood can legally be moved freely between counties within the state, but the movement of firewood is still discouraged unless it has been properly treated. It is important to remember that, in addition to EAB, firewood can harbor a variety of damaging insect pests and diseases and movement of firewood can introduce these pests to areas that are not yet infested. Given the importance of firewood as a potential pathway for spreading EAB to new areas, moving uncertified hardwood firewood out of EAB-quarantined areas is illegal and punishable by a fine up to a $7,500 per violation per day.
Only firewood that has been certified by the Minnesota Department of Agriculture (MDA) or United States Department of Agriculture (USDA) may be moved outside quarantined areas and must bear the MDA certificate or USDA certificate on the label. Although elimination of the federal EAB quarantine is being considered, the interstate movement of EAB-regulated articles continues to be regulated at the federal level by the USDA Animal and Plant Health Inspection Service (APHIS) in partnership with the individual states included in the federal quarantine.
Additional information on moving firewood in Minnesota & Wisconsin:
Additional information about the discoveries of EAB in Rice County and Mower County, as well as general information about the status of EAB in Minnesota and North America and EAB quarantines, are available through the following links:
History of EAB in North America and in Minnesota and Neighboring States
Native to east-central Asia, emerald ash borer (EAB; Agrilus planipennis), classified in the taxonomic order Coleoptera (beetles) and the family Buprestidae (metallic woodboring beetles; also called jewel beetles and flat-headed borers), was first documented in North America in 2002 in southeastern Michigan (Detroit area) and across the border (the Detroit River) in Windsor, Ontario, in Canada and has since spread to 35 states in the Eastern, Midwestern (including Minnesota), and Mountain regions of the United States and the far southern portions of five Canadian provinces (Ontario, Manitoba, New Brunswick, Nova Scotia, and Quebec). In the United States it is estimated that seven billion trees are threatened and as much as 35% of the tree canopy in some municipalities. Capable of attacking healthy trees, hundreds of millions of ash trees (Fraxinus spp.) have already been killed in infested areas and all three species of ash that are native to the Upper Midwest, including Minnesota, are susceptible to attack including white ash (Fraxinus americana), black ash (Fraxinus nigra; most common in northern Minnesota and the most numerous species in the state), and green ash (Fraxinus pennsylvanica; also called red ash; the most widely distributed species in the state and the most commonly planted species in designed landscapes). Based on the historical progression of the EAB epidemic, 99% of ash trees in infested areas will ultimately be killed by this devastating insect. As a result, it is estimated that as many as one billion ash trees could be at risk in the state of Minnesota alone.
In Minnesota, EAB was first documented in Ramsey County almost 11 years ago in May 2009; EAB was also confirmed in Hennepin and Houston Counties the same year and all three counties were subsequently quarantined by the Minnesota Department of Agriculture (MDA). Winona County was added to the list of quarantined counties in 2011. Since then, the destructive, non-native emerald ash borer beetle has continued to spread to new areas and, as of this writing, 23 of Minnesota’s 87 counties (24%) are currently subject to complete or partial quarantines in an attempt to prevent the spread of emerald ash borer in the state. Twenty-two (22) counties are covered by complete quarantines including Anoka (2015), Brown (2019), Chisago (2015), Dakota (2014), Dodge (2016), Fillmore (2015), Goodhue (2017), Hennepin (2009), Houston (2009), Martin (2017), Mower (2020), Nobles (2919), Olmsted (2014), Ramsey (2009), Rice (2020), Scott (2015), Wabasha (2016), Washington (2015), Winona (2011), Wright (2018), Stearns (2019) and Steele (2019) Counties. A partial quarantine (established in September 2016 and formalized in March 2017) is also in effect for the southeastern corner of St. Louis County including the city of Duluth.
Originally the quarantine in St. Louis County was limited to Park Point in the city of Duluth, but was subsequently expanded to include the southeastern portion of St. Louis County including the entire city of Duluth in response to additional EAB finds. The remainder and majority of St. Louis County is not currently under quarantine. EAB is also present across the border in Superior, WI (Douglas County), where a quarantine went into effect in 2013. Although the infestations in Duluth, MN, and Superior, WI, are in areas where winter temperatures tend to be moderated by Lake Superior, these infestations are close to the larger populations of ash trees in the colder, more forested areas of both states. As a result, depending on the actual winter temperatures experienced, we may soon learn whether these infestations will be able to expand and have a significant effect on ash trees in the adjacent, colder areas where laboratory studies have suggested EAB populations may not be able to reach tree-killing levels as a result of the winter temperatures that are typically experienced in these regions. With the exception of the finds in the city of Duluth (St. Louis County), Martin County, Stearns County, and one of the most recent finds in Brown County, the current EAB infestations in Minnesota are limited to the core of the Twin Cities metropolitan area and the southeastern corner of the state.
Fortunately, the spread of EAB in Minnesota has generally been slower than what has been experienced in other states, but this trend may be changing. And although the spread of EAB and the number of trees that have been lost in Minnesota have been atypical compared to the infestations in other states, it is possible that EAB is beginning to spread more quickly in Minnesota. Beginning with the first EAB finds in Minnesota in 2009, six (6) counties were quarantined during the first six years (2009-2014) of the Minnesota invasion, while quarantines have been implemented in another seventeen (17) counties since then (2015-present). Whether additional new infestations will be found this year and whether the increase in finds in recent years will become a longer-term trend remains to be seen. In the shorter term, the widespread subzero temperatures experienced across the state during the winter of 2018/19 may have helped as it has been variously estimated that 70-80% of the overwintering EAB larvae may have been killed as a result of temperatures in the -20 to -30ºF range, or colder, in many areas of the state.
Emerald ash borer is also present in Wisconsin (although EAB has not been documented in every county, the entire state is now under quarantine), Iowa (mainly in eastern and southern counties), a few counties in east-central Nebraska, and in southeastern South Dakota (Sioux Falls; May, 2018), but has not yet been found in North Dakota. The South Dakota infestation and the Nebraska infestations, plus infestations in a small number of counties just across the state borders in eastern Kansas, Oklahoma, and Texas, and an isolated infestation in Boulder County, CO, are currently the western-most infestations in North America. In Canada, the EAB infestation is currently limited to extreme south-central Quebec, southeastern Ontario and isolated infestations in Thunder Bay, Ontario (located about 45 miles north of the Minnesota border), the cities of Edmunston and Oromocto in New Brunswick, the city of Halifax in south central Nova Scotia, and in Winnipeg, Manitoba. The introduction of EAB in North America, which likely occurred in the early 1990s, was a human-mediated event and, more recently, the long-distance and initially-isolated infestations of EAB in the Minneapolis/St. Paul metropolitan area, the Duluth/Superior area, Rhinelander (WI), Thunder Bay (Ontario, Canada), Winnipeg (Manitoba, Canada), the Kansas City (MO/KS) metropolitan area, the southwestern Arkansas/northern Louisiana/northeast Texas region, Boulder County (CO), and Sioux Falls (SD) were also almost certainly human-mediated introductions. Along with other control efforts, all concerned must be constantly diligent and take great care to avoid moving EAB-infested materials, including firewood, to non-infested areas to slow the spread of this devastating insect pest.
Although the presence of EAB in 51 of Wisconsin’s 72 counties (71%) is a depressing statistic, it is important to note that, with the exception of areas in the far southeastern corner of the state and a few counties bordering Minnesota in the southwestern part of the state, most of Wisconsin (approximately 80%) remains EAB-free. The situation in Minnesota is even better where only 23 of the state’s 87 counties (about 26%), almost exclusively located in the Twin Cities metropolitan area and several counties in southeastern Minnesota and along the Iowa border (Martin and Nobles), are currently under full or partial quarantine in an attempt to slow the spread of EAB in the state. The reality is that most of Minnesota, Wisconsin, Iowa, and South Dakota remain EAB-free and preventing the spread of EAB to new areas should remain a top priority. This is a very important reality and message that should not be overlooked.
As nursery and landscape professionals are well aware, EAB poses a serious threat to untreated ash trees growing in designed landscapes and ash trees growing in native ecosystems across the state. Keeping this in mind, Minnesota Nursery and Landscape Association (MNLA) members, and especially those firms that do business in quarantined areas and across state lines, should stay informed about additions to the federal and state EAB quarantined areas and changes in quarantine requirements. Nursery and landscape firms should also continue to educate their customers about the threat of EAB and how to manage and prevent the spread of this devastating insect pest including the treatment of valuable ash trees in residential and commercial landscapes. Treating healthy ash trees has been shown to be a highly effective means of protecting valuable ash trees from attack by EAB in landscape settings and maintaining the many, important, socioeconomic and environmental benefits provided by these trees; benefits that would not be regained for generations if such trees are allowed to become infested or are simply removed and replaced. Minnesota nurseries and garden centers are also important sources of information for the landscaping public on site-specific plant selection and providers of the landscape trees and other landscape plants that can provide the increased diversity needed to reduce the impacts of the growing list of invasive insects and diseases that threaten designed landscapes in Minnesota and beyond.
Nationally, emerald ash borer has now been documented in 35 states. As a consequence, the USDA Animal and Plant Health Inspection Service (APHIS) has proposed the elimination of the federal EAB quarantine which would eliminate the federal regulations on the movement of materials that could harbor EAB between states; a formal decision was expected in 2019, but there has been no announcement yet (as of April, 3, 2020). Federal resources would still be used for Managing EAB including biocontrol using three species of parasitic, stingless wasps (Oobius agrili, Spathius galinae, and Tetrastichus planipennisi; Hymenoptera: Encyrtidae, Braconidae, and Eulophidae, respectfully) that are natural enemies of EAB that have been approved for release in the United States. All three species are host-specific parasitoids that attack EAB eggs (O. agilli) or larvae (S. galinae and T. planipennis). If EAB is deregulated at the federal level, it is likely that states where EAB has not yet been documented, primarily states west of the Mississippi River, would enact exterior quarantines that would restrict the movement of ash trees and ash wood products into these states from infested areas. In anticipation of a possible decision to abandon the federal quarantine, the MDA has developed a modified version of the Minnesota quarantine with the goal of filling the gaps that would result should the federal quarantine be eliminated. The MNLA has commented on the proposed changes to the state quarantine and has expressed support for continuing the state quarantine and the MDA’s other EAB management efforts. We will keep the MNLA membership informed about any changes to the federal or state EAB quarantines.
Selected Links to Additional Information About EAB:
- General information about the Minnesota Department of Agriculture (MDA) emerald ash borer (EAB) program and links to more specific information about EAB in Minnesota
- The text of the Minnesota EAB formal quarantine (Version 14; May 30, 2019). The quarantine addresses the use and movement of regulated materials which include the insect itself (all life stages); all plants and plant parts of the genus Fraxinus, including nursery stock, scion and bud wood, logs, branches, stumps, roots, woodchips and mulch (composted or not), hardwood firewood (firewood from any non-coniferous species), and other materials deemed to be a risk for the spread of EAB by the Minnesota Commissioner of Agriculture.
- A publication developed by the Minnesota Department of Agriculture entitled Guidelines to Slow the Growth and Spread of Emerald Ash Borer is a good source of information and guidance on preparing for, detecting, and managing healthy and infested ash trees, EAB populations, and tree waste in Minnesota.
- An interactive, searchable, map of specific EAB finds and generally infested, quarantined, and biocontrol areas in Minnesota.
- A summary of the status of EAB in Minnesota, along with information about some of the activities being pursued by the MDA to better understand and track EAB in the state.
- The recently-updated publication entitled Managing Ash Woodlands: Recommendations for Minnesota Woodland Owners (2019; University of Minnesota Digital Conservancy).
- Information about research on emerald ash borer being conducted at the University of Minnesota through the Minnesota Invasive Terrestrial Plants and Pests Center (MITPPC).
- The current USDA APHIS quarantine map is available at .
- As mentioned previously, a new video entitled How to Look for Emerald Ash Borer Now (April 1, 2019) is available from University of Minnesota Extension.
- Additional information about insect pests in Minnesota, including EAB
- Information from Extension specific to EAB
- Additional information about EAB in Wisconsin
- Additional information about EAB in Iowa
- Additional information about EAB in South Dakota
- Additional information about EAB and its management is also available on the My Minnesota Woods website (University of Minnesota Extension - Forestry).
- And finally, additional information regarding the status of EAB in North America is available on the Emerald Ash Borer Information Network website and from the United States Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS).
If you have questions or comments regarding this MNLA Regulatory Update or the status of EAB in Minnesota and neighboring states, or other places in North America, contact Jim Calkins, MNLA Regulatory Affairs Manager, at firstname.lastname@example.org.