With the start of summer holidays, highway traffic is set to increase as people take road trips to the beach, visit family members and fun places.  Those of us who have been commuting all year have already been admiring the beautiful purple, white and lavender coloured flowers along the highway. Sad to report that these flowers, commonly known as Dame's Rocket, are also invasive! Even worse, the first website that came up when I googled this plant to see what came up was how to grow it?!

While it is not found on any Michigan invasive species watch list, nor listed on any seed laws by MDARD, they are invasive and are included on the US Forest Service's list of invasive species.  Dame's rocket is a biennial plant that is native to Eurasia and belongs to the same family as another common invasive plant, the garlic mustard.  During the first year, the plant produces a short rosette with pointy lance shaped leaves that stay green throughout the year.  In the following year it can grow up to four feet in height, producing white, purple and/or lavender coloured flowers with four petals. The lag time in flowering is why growth is noticed in bi-yearly waves.  They are typically found along highways, roads, woodlands and open areas as they prefer moist areas with proper drainage. With the ability to bloom for most of the summer and high rate of seed production, they can quickly escape gardens and spread to other areas. Due to their popularity, seeds are often harvested and sold in wildflower seed packets (look for the scientific name " Hesperis matronalis") or even as stand alone plants.

While very pretty, these flowers are quick to crowd out native plant species, and thus reduce plant biodiversity. They are thought to be allelopathic, meaning they can produce chemicals that prevent other plants from growing around them.  If the infestation gets to be large enough, it can impact water drainage, prevent the emergence of tree seedlings, and change what organisms utilize the area.

If you have this plant in your yard there are a couple things you can do to manage it.  First and foremost, do not plant more of it, and check seed packets for this species. They can be pulled by hand if the infestation is small, but it is important to remove the entire taproot and dispose of the plant in the landfill. When the plant is flowering, you can take a pair of shears or scissors and cut the plant from the flower up (prior to it going to seed).  Herbicide may also be used, but should be used according to product's label.   Foliar spray using glyphosate or triclopyr can be used, and is more effective when the native plants are dormant and the basal rosettes are green (WDNRb, 2019).  For more information, please see the US Forest Service fact sheet (click here). ​

For more information:

USDA. 2019. Weed of the Week: Dame's Rocket. Date Accessed: June 5th, 2019.  Website:  
www.invasive.org/weedcd/pdfs/wow/dames-rocket.pdf

WDNR. 2019a. Invasive Species: Dame's rocket (Hesperis matronalis).  Date Accessed: June 5th, 2019. Website:
https://dnr.wi.gov/topic/invasives/fact/damesrocket.html

WDNR. 2019b. Dame's rocket (fact sheet). Date Accessed: June 5th, 2019. Website:
http://learningstore.uwex.edu/Assets/pdfs/A3924-06.pdf

You may have heard about non-profit or environmental organizations recruiting members of the public for "garlic mustard pulls". But what exactly are those plants, and why are they bad? 

Garlic mustard is found in all of the Great Lakes states, with the highest density located in the eastern half of the country (as shown in the below EDDMap, 2019). This invasive species was introduced from Europe as it was used in food (e.g. salads, pestos, soups etc...), soil erosion control and for medicinal purposes. Garlic mustard  got its name from the smell it emits when the leaves are crushed (a strong garlic like scent) and its resemblance to the mustard plant. This plant was able to spread out of control due to reasons such as one garlic mustard plant being able to produce up to 8000 seeds in one season, it emerging earlier than many native flowers, lack of a natural predator and is not preferred by deer as a food source.  Impacts of this flower include reducing area biodiversity in the understory of forests, shades out native wild flowers such as trillium's and spring beauty. They have allelopathic compounds that may limit the germination of seeds of other species.

Garlic mustard takes two years to complete its life cycle. During the first year, plants form basal rosettes close to the ground, and can over winter in that form, all the while continuing to perform photosynthesis. During the second year, it will grow taller (up to 4 ft tall), and produce small, four petaled flowers. Leaves have a slight triangular shape and are sharply toothed around the edges. They typically flower in Michigan during the month of May.

If you have this plant on your property, there are a few management strategies you can employ, and management should focus first on satellite populations and for larger infestation, from the peripheral part of the infestation moving inwards towards the epicenter.  Hand pulling can be effective for small populations, and the entire plant (including the roots) needs to be pulled up and bagged immediately. For larger infestations, herbicide may be more effective. Detailed management options summarized by the State of Michigan can be found here.

​

For more information:

Center for Invasive Species and Ecosystem Health. 2019. Garlic Mustard. Date Accessed: May 22, 2019. Website:  https://www.invasive.org/browse/subinfo.cfm?sub=3005

EDDMapS. 2019. Early Detection & Distribution Mapping System. The University of Georgia - Center for Invasive Species and Ecosystem Health. Available online at http://www.eddmaps.org/; last accessed May 22, 2019.

MDNR. 2019. Garlic Mustard (Species Profiles and Reporting Information).  Website:  
https://www.michigan.gov/invasives/0,5664,7-324-68002_71240_73853-379483--,00.html

The Nature Conservancy. 2019. Journey with Nature: Garlic Mustard. Date Accessed: May 22, 2019. Website:
​https://www.nature.org/en-us/about-us/where-we-work/united-states/indiana/stories-in-indiana/garlic-mustard/

With most of the snow melted and the ground warming up, many people are getting a head start on preparing their yards for planting and landscaping by clearing brush and dead plant material from last year.  For others, many are preparing their yard for landscaping for the first time as new home owners/renters, possibly dealing with unknown plants and vines. Before you cut or clear away any brush, make sure you know what you are removing. Many invasive species may look like they are dead on the surface, but, they are very much alive.  Cutting, mowing and pulling untreated brush may result in an even larger infestation during the summer season. 

If you see tall stalks that are hollow, they might be Japanese knotweed. This species of plant grows aggressively and has the potential to damage sidewalks, driveways and the foundation of buildings.  To effectively manage Japanese knotweed, it is important to understand the growing cycle of the plant.  Japanese knotweed is a perennial shrub that has an extensive underground rhizome system (essentially an underground horizontal root system). During the spring, the rhizomes send up shoots that will grow through the leaf litter, often looking like asparagus. When the growing season ends at the end of summer, the plant begins to redistribute its energy towards its roots in order to prepare for its dormancy period. It is at this time herbicide treatment efforts should be implemented for maximum effectiveness.  During winter, the above ground vegetation turns brown and brittle, as is shown in the picture below.  If the Japanese knotweed has not been treated, do not cut or mow the stalks as it may stimulate the roots and rhizomes to send up more shoots. It is important to note that even a small fragment of root or rhizome can become an established plant, and all loose pieces should be landfilled in lieu of composting.
​

With winter, and hopefully all of Michigan's "false springs" soon to be ending, many gardening and landscaping enthusiasts are planning their spring fruit, vegetable and flower gardens. One thing we hope gardeners will consider, is to choose native plant species when possible.

Some of the usual reasons overheard for not planting native species is that they aren't as pretty, does not fit it with traditional/cultural norms, lacks the landscape service desired, no time to research what plants are native, do not know where to buy native plants, expense etc...  Thankfully, there are many options available that achieve both the functional and aesthetic requirements, and many resources available in helping determine what species are native to your region. In this article, we will discuss some of the benefits to planting native plant species and identify sources for the readers to determine what species are native to their region of interest.

Native plants have many advantages and benefits to both the environment and gardeners. Native species are well suited to local soil and environmental conditions, thus requiring less fertilizers, pesticides and less watering.  Local plants and wildlife have a long and complex relationship that has evolved over time, with many birds, insects and animals relying on native plants for food and shelter.  Native plants will help in maintaining species biodiversity by providing food and habitat needs not obtained from ornamental and invasive species.  Residents and municipalities can also create rain gardens using native species.  Rain gardens will help reduce pollutants such as bacteria and gasoline from entering the water system, and reduce flooding by absorbing excess rainwater. Native plants can also also help keep invasive species at bay, preventing loss of habitat and monoculture type of lawns and gardens. Various plants and grass species have also been used to help prevent soil erosion near shorelines and farmlands.

Michigan has a variety of native plants that grow at different times of the season, allowing your garden to be lush and beautiful all summer long.  However, it is important use ethically sourced materials when finding plants to grow in your garden.  Over the years, people have illegally collected plants from federal, state and local parks, causing harm for years to come. If not harvested properly, plants can die, and the seed bank in the soil can be lost. Loss of plants also impact pollinator species and other animals that need them for food or shelter.  Unique plants such as carnivorous plants and orchids are commonly harvested due to their rareness and beauty, thus preventing others from being able to view them.  Before you pick plants, make sure you know the law, have proper collection permits (click here for federal information) and know what you are doing.  

In order to identify what plants are native to your region, there are several websites and organizations that can help!  If you are looking for native plants that attract particular birds, the National Audubon Society has a search engine where you can type in your zip code (click here). If you want to search for native plants based on region, soil moisture, amount of sunlight, pollinators/natural enemies, the Department of Entomology at Michigan State has a website that divides Michigan into sourthern Lower Michigan, northern Lower Michigan and the Upper Peninsula (click here). For aquatic options for those living near water bodies, the Michigan Natural Shoreline Partnership has lists based on if you want plants below the water level, between the water level, above the water level and/or upland areas (click here).  

Once you have identified what plants you are interested in obtaining, one useful site to visit is the Wildflower Association of Michigan. They  have a list of members who produce and grow Michigan genotype seeds and plants ( click here).  Hopefully this post has provided some good reasons for you to consider planting native species in your garden, some helpful resources in figuring what is native vs. not, and where you can buy them.  Happy gardening folks!


For More Information:

Dept. of Entomology.  2019.  Regional Plant Lists
https://www.canr.msu.edu/nativeplants/plant_facts/local_info/south_lower_peninsula
​
Michigan Department of Transportation. 2019. Stormwater Management: Rain Gardens
https://www.michigan.gov/stormwatermgt/0,1607,7-205-30387-212265--,00.html#michiganave ​

National Audubon Society. 2019. Native Plants Database.  https://www.audubon.org/native-plants

Wildflower Association of Michigan. 2019. Sources of Native Plants.  https://www.wildflowersmich.org/index.php?menu=9

USDA. 2019. Ethics and Native Plants.  https://www.fs.fed.us/wildflowers/ethics/index.shtml

USDA. 2019.  Collection Permits.  ​https://www.fs.fed.us/wildflowers/ethics/permit.shtml

By Shikha Singh, PhD

Grass carp is a fish species with a voracious appetite for aquatic plants, and can eat up to 40 % of their body weight per day! Highlighting one of the reasons why this species was introduced to the United States from Taiwan and Malaysia, to control aquatic weeds.

Asian carp are a group of four species of fish that include Bighead, Silver, Black and Grass carp.  Common features of all of these fish include they are fast growing, have a big appetite, can get large, and eat plankton.  A lot of attention and media coverage has been on the Bighead and Silver carp as they have been slowly moving towards the Great Lakes via the Mississippi River, and there is concern that they will breach the various barriers and decimate the Great Lakes fisheries by out competing the native species for food and habitat. Popular videos show them jumping behind motor boats and hitting boaters.  To add insult to injury, it seems that the invasive Eurasian watermilfoil plant is not a species preferred by carp, so they are not likely to help control aquatic invasive plants. Of the above species, Grass carp is already here.   

Anglers have reported catching Grass carp for the past 40 years, however, they were thought to be sterile carp which thought to have escaped various ponds or stocked lakes (where they were brought in to control weeds). Legally introduced Grass carp were tested for sterility prior to being introduced, as posted by the National Park Service (NPS) website. Because Grass carp eggs require high flow, oxygen rich water for reproductive success (eggs will not be successful in hatching if they sink to the bottom), it was hoped that if spawning Grass carp were in the region, this limiting factor would keep them from being a problem.  However, in 2015, researchers collected eggs and confirmed that Grass carp were naturally spawning within the Great Lakes tributary (Embke et. al. 2016), and sampling efforts by USGS/Dr. Christine Mayer's group found larval Grass Carp in the Maumee River (confirmed via genetic sequencing).  

These recent findings are concerning, and hopefully will propel Grass carp into the limelight as a species to keep an eye out for, alongside the Bighead and Silver. This also highlights the need for anglers and commercial fishermen to inspect their catch for Grass carp and report sightings to State officials and/or the local CISMA.  To prevent the spread of Grass carp, make sure you know what species are in your bait bucket as juvenile carp do look similar to other fish such as Alewife and Shiners. This caution also extends to bait bought at large retail stores.  Do not dump unused bait back into the lake/river, dispose of in the trash.  To see a detailed guide to what juvenile carp and Alewife/Shiners look like, please click here to access the MDNR brochure.


For More Information:
Embke, H.S. et al. 2016.  First direct confirmation of grass carp spawning in a Great Lakes tributary. J. Great Lakes Research. 42(4): 299-903 

MDNR. 2019. Asian Carp: Know the Facts and Learn How You Can Help. 
https://www.michigan.gov/documents/dnr/asian_carp_brochure-smaller_388343_7.pdf

NPS. 2019. Grass Carp. Date Accessed: 3/12/2019. https://www.nps.gov/miss/learn/nature/ascarp_grass.htm

USGS. 2019. Newly Hatched Invasive Grass Carp Found in Maumee River, Ohio.
https://www.usgs.gov/news/newly-hatched-invasive-grass-carp-found-maumee-river-ohio

​This being the end of "National Invasive Species Awareness Week", I wanted to draw attention to one of the most classic and quintessential examples of how invasive species have been introduced by people, resulting in great devastation to the local ecosystem.  This post will take us to the warm and tropical state of Florida, where the exotic  Burmese python has been thriving since being introduced in the 1980s! Originating from Southeast Asia, Burmese pythons are heavier and stronger than any native snake found in Florida. Growing up to 20 ft in length, they are strong enough to eat adult deer, bobcats, rabbits, birds and alligators (sometimes ending poorly for both the python and alligator!)

Scientists have reported decreases in various animals in the Southern Florida region.  Dorcas et. al. (2012) looked at the presence of mammals in the Everglades National Park (ENP) where common roadkill organisms found between 1993 and 1999 were raccoons, Virginia opossums and rabbits. Pythons were considered established in the area in the year 2000.  From 2003 to 2011 they reported decreases in the following animals with percentage in parenthesis:  raccoons (99.3%), opossums (98.9%), white-tailed deer (94.1%), and bobcats (87.5%).   No foxes or rabbits were found during this time period.  In peripheral areas where pythons were recently documented, Dorcas et al. (2012) found lower encounter rates by (in parenthesis) for the following organisms:  raccoons (89%), opossums ( 44%), and foxes (83%). Authors further wrote " Observation frequency of raccoons and opossums at two extralimital locales were similar to historical sighting frequencies in ENP and were substantially higher than sighting rates in recent surveys of ENP and peripheral locales ".  This suggests that the Burmese python have a role to play in these findings. Some species such as turtles may benefit as raccoons, foxes and opossums have been known to decimate turtle nests. 

Invasive species are also problematic because they are easily able to adapt to their new areas.  Not only does the Florida environment contain proper food and habitat for them, but scientists have found evidence that they can breed with other species.  Hunter et al. (2018) collected Burmese python tissue samples from Everglades National Park and found some had genetic signatures of Indian rock python in their mitochondrial DNA.  While it was not known if the interbreeding occurred in the wild or in captivity, the potential exists for it occur in the wild, and may result in progeny that can adapt to a broader type of habitat, and be faster/sleeker than Burmese python that has no other species in its DNA.  

There are two main ways this (and other invasive snakes such as the Common boa and N. African python) have made their way into the Everglades, forests and cites. The first being released by careless pet owners who either didn't do their research on how big they get, understand how much care/money was needed, or lack a future plan for unexpected changes in health/finance...). The second involves snakes escaping due to unfortunate environmental circumstances such as floods, hurricanes, fires etc...  It is without saying that no pet, be it a snake, cat, dog, fish etc. should be released into the wild. Always have a back up plan, contact reputable owners/retailers or local organizations for help in re-homing any organism that needs it.  If you cannot commit to a pet for the entirety of its life, there are many groups, pet owners and zoos that do outreach and education events where you can responsibly interact with these beautiful organisms.
​

For more information:

Dell'Amore, C. 2012. Pythons Eating Through Everglades Mammals at "Astonishing" Rate?.  National Geographic Website:  
https://news.nationalgeographic.com/news/2012/01/120130-florida-burmese-pythons-mammals-everglades-science-nation/

Dorcas. M. E. et. al. 2012. Severe mammal declines coincide with proliferation of invasive Burmese pythons in Everglades National Park.  PNAS. 109(7):2418-2422. 
https://www.pnas.org/content/109/7/2418

Hunter, M.E et. al. 2018. Cytonuclear discordance in the Florida Everglades invasive Burmese python (Python bivittatus) population reveals possible hybridization with the Indian python (P. molurus). Ecology and Evolution. 8(17): 9034-9047.  
https://onlinelibrary.wiley.com/doi/full/10.1002/ece3.4423

Recently, several articles and news outlets have been perpetuating the claim that the extreme cold weather due to the polar vortex wiped out 95% of the Brown Marmorated Stinkbugs.  I just wanted to post a quick response regarding those claims.  It is true that extreme cold weather can kill ​stinkbugs, especially if those temperatures persist over time. However, timing is everything!

When the temperatures start dropping, adults begin to migrate from open fields and orchards to structures/homes and forests to seek respite from the cold. In Michigan, this starts to happen in September until about November. This means living rent free in your couches, walls, barns, garages, sheds etc...  They can also crawl into crevices of trees, pavement cracks as well. While the polar vortex was happening, they were likely, snug as a bug in a rug. 

​These news sources have also cited a 2014 paper to back up these claims, but the problem with this is that lab conditions are not necessarily transferable to real life scenarios. Mental Floss directly contacted the researcher who echoed these sentiments regarding his work being portrayed as such.

If the cold snap happened in September or October, perhaps we could have a more robust discussion on impacts to the population, as this would be when they are still out and about. At this time, we have no reason to believe that 95% of the stinkbugs have been killed.  For  more information on how invasive species do cope with cold weather, please see the below post. To keep out stinkbugs, make sure you have properly fitted window screens, doors without gaps and screens on any vents that connect outside!

​
​For more information:

Wilson et al. 2017.  Managing Brown Marmorated Stink Bug in Michigan Orchards. Michigan State University Extension. Website:
https://www.canr.msu.edu/ipm/uploads/files/BMSB/MichiganBMSBMngtGuideJuly2017.pdf

Petsko, E. 2019.  Sorry, But Last Month's Polar Vortex Didn't Wipe Out 95 Percent of Stink Bugs. Mental Floss.  Website:
http://mentalfloss.com/article/574447/polar-vortex-didnt-kill-95-percent-of-stink-bugs

​When you see a new and unfamiliar weed growing in your garden or lawn, what is the first thing you do? First instincts are to pull it out, mow over it, and spray herbicides...only to see it grow back next month/year with a vengeance.  Not all species are created equally...and that means some species have characteristics about their life cycle or biology that makes them harder to manage, and ultimately eliminate!

This post will discuss two of the many reasons why homeowners are often frustrated and unsuccessful in managing small scale infestations on their property, rhizomes and seed banks!  Rhizomes are a horizontal plant stem that grow underground and are capable of forming new roots and stems. Unless you are able to pull out the entire plant, including all and any fragments, new plants will pop up when mechanical removal strategies are used.  Any plant produced from rhizomal propagation is genetically identical to the parent plant. Common examples of invasive species that have rhizomes include Japanese knotweed and Phragmites. The key to dealing with these plants includes targeting treatment options at the rhizomes as the plant will store a lot of its energy here, especially when the growing season is coming to an end. In the case of Japanese knotweed, treatment may include foliar spraying to thin out the infestation, and then injecting herbicide into the base of the plant to kill the roots and rhizomes.
​
Many invasive plants produce copious amounts of seeds each year. Each Japanese stiltgrass plant can produce 100 to 1000 seeds per plant, and those seeds may remain viable for up to five years. Those seeds are often deposited into the soil nearby, or transferred to other areas via wind, rain and other organisms.  Depending on how long the infestation has been a problem, there may be a large and viable seed bank in the area. When trying to manage high seed producing plants, timing is everything! Mechanical pulling can be used for plants that have shallow roots or small infestations, else herbicide.  One thing to consider is allowing the plant to grow and then harvest prior to the plant flowering to avoid seed dispersal, and potentially minimizing the amount of plants growing in the area . Trying to mow while the viable seeds are present on the plant could be a recipe for disaster and allow for spread via wind or equipment if it is not decontaminated properly!

Regardless of whether the plant propagates using rhizomes, seeds or both, management efforts will be a multi year effort in order to eliminate the entire plant network and reduce the seed bank.  For more information, please visit the below links!

References:

Nitzsche, P. and P. Rector.  Japanese Stiltgrass Control in the Home Lawn and Landscape. New Jersey Agricultural Experiment Station. 

Michigan Department of Environmental Quality. Phragmites information page.  

An interesting study looked at a large infrastructure development project and identified areas of high risk for invasion by non native species. The China’s Belt and Road Initiative project involves six proposed economic corridors and 121 countries. Researchers examined habitat suitability and risk of invasion, finding 14 hotspots containing both high habitat suitability AND high risk. While N.America was not a part of this project, we have trading partners that intersect with with countries that are. I encourage you all to look at some of the maps they produced and factors that went into the modelling process!  This highlights a need for biosecurity protocols and increasing local capacity to support monitoring efforts/rapid response in preventing invasive species from becoming established.

Please check out the research entitled "Risks of Biological Invasion on the Belt and Road" by Liu et. al. (2019) found here.

​

As I write this post, it is currently a brisk -11°C (13°F) with a windchill of -17°C (2°F) outside, and scheduled to be even colder over the next few days.  Most of us are likely going to stay inside, however, many other organisms do not have that option.  Insects have a few evolutionary tactics that allow them to survive these harsh frigid conditions, including some invasive species.
 
Most insects do not survive winter, instead, they lay eggs and die when the cold hits, others use "freeze avoidance" or  "freeze tolerant" strategies.  Freeze avoiding insects can try and find a dry area to hibernate (or in the insect world, diapause, a dormant state). Others like the invasive Japanese Beetle grub will seek shelter and burrow in the soil (have been found up to 6 ft deep!), which has a higher heat capacity than air, thus warmer than then ambient air.  Freeze tolerant insects have the unique ability to replace the water in their body with an anti-freeze like solution called cryoprotectants , which supercools the fluids within the insects body by increasing the solute concentrations within cells.  Examples of cryoprotectants include sorbitol, mannitol and ethylene glycol, however, one of the more common ones used by insects is glycerol. Freeze tolerant insects can survive ice formation within their bodily tissues to some degree.   

In North America, the invasive insect, Emerald Ash Borer has changed the landscape in states such as Michigan and Minnesota by killing thousands of Ash trees.  They were thought to have arrived from Asia via wood packing materials and have been able to survive the cold temperatures found in Michigan.  Researchers found that the Emerald Ash Borer was found to have a supercooling point (the temperature when insects do freeze). A few different studies found that that the supercooling point to be -30.6°C (-23°F) in Ontario (Sobek et. al., 2009) and between -26.4 to -23.0°C (-15.5 to -9.4°F) in China (Wu et al., 2007). Venette and Abrahamson (2010) found the average supercooling  point for larvae in Minnesota was -25°C (-13°F).

The sap sucking Hemlock Woolley Adelgid (HWA) is another invasive species that originated from Japan and China, and has been detected in Michigan. They possibly came to Michigan from trees that were already infested and transported in from other states.  HWA reproduce asexually and have two overlapping generations in one year (progrediens and sistens) with the sistens being the generation that spans early summer to mid spring and produce approximately 300 eggs. They are able to be transferred to other trees via wind and other animals.  Sistens feed and develop during the winter, but are susceptible extreme cold weather as well, 90% mortality was found if temperatures dropped below -22°F (McCullough, D.G.  2015).

While cool weather can kill potential invasive insects, it is not something we can count on to completely eradicate invasive species from the area.  In the case of the Japanese beetles, unless there is a quick freeze that prematurely hardens the soil and prevents the grubs from burrowing, they can survive cold temperatures.  Some insects that utilize trees for protection may survive cold temperatures as not all sections of a tree cools equally.  Sunshine, wind, direction the tree is facing may protect insects from mortality.  There exists the potential for cold tolerance to be genetically linked. In this case, the few individuals that survive may pass on this genetic feature to future generations, and can quickly reproduce and rebuild their numbers, producing a population that is resistant to cold weather than previous populations.

The bottom line?  Insects have evolved pretty interesting strategies to survive winter. Cold weather may help decrease insect numbers, but is not a permanent solution for large scale infestations.  Prevention is important and this means checking your gear, equipment and shipments for invasive species.  In the case of the two species mentioned above, transporting firewood from other regions can also bring in these insects and should be avoided!


For more information:
McCullough, D.G. 2015. Hemlock Woolly Adelgid:  A little insect that means big trouble for hemlock trees in Michigan. MSU Extension Bulletin (E-3300). Found:  https://www.michigan.gov/documents/invasives/HWA_Bulletin_518429_7.pdf

Sobek, S., J.C. Crosthwaite, and B.J. Sinclair. 2009. Is overwintering biology of invasive insects affected by climate change? Plasticity of cold tolerance in the emerald ash borer (Agrilus planipennis). 94th Annual Meeting of the Ecological Society of America. August 2-7, 2009 (Abstract).

Venette, R. C. and M. Abrahamson. 2010. Cold hardiness of emerald ash borer Agrilus planipennis: a new perspective. In: Black ash symposium: proceedings of the meeting; 2010 May 25-27;. Bemidji, MN. Cass Lake, MN: U.S. Department of Agriculture, Forest Service, Chippewa National Forest. 5 p.

Wu, H., M.-L. Li, Z.-Q. Yang, and X.-Y. Wang. 2007. Research on cold hardiness of emerald ash borer and it’s [sic] two parasitoids, Spathius agrili Yang (Hym., Braconidae) and Tetrastichus planipennisi Yang (Hym., Eulophidae). Chinese J. Biol. Contr. 23: 119-122 (Chinese).