2023 CEQ Annual Report

Invasive Disruptors

Climate Change Indicator


Invasive species are species that are not native to Connecticut that exhibit an aggressive growth habit and can out-compete and displace native species. It is expected that more invasive species, both plant and animal, will arrive, become established, and flourish as a consequence of the warming climate that is making Connecticut more hospitable to species that do not tolerate cold weather. Further, climate induced stress, rising temperatures, and extreme weather in an ecosystem can facilitate invasive pathways. The adverse impacts of invasives affect all the state’s ecosystems, including its waterways, natural lands, working lands and developed landscapes. In addition, the economic and human health costs of unchecked invasive species can be high. In 2022, the Council completed an update ("INVASIVES": PREVIOUSLY DESCRIBED and NEWLY ARRIVED) to the Council’s 2002 report, Great Infestations, that included recommendations for the control of invasive species in Connecticut. Preventing invasive species from taking over and disrupting Connecticut’s landscapes and waterways, requires advanced planning, vigilance, maintenance, coordination and prioritization of the expenditure of human energy and of public funds.

Asian Tiger Mosquitoes68

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In 2023, there was an increase of Asian tiger mosquitoes collected* in the state, which might have been the result of warm temperatures during the winter and above average precipitation during the summer. The range of the Asian tiger mosquito is expanding in the United States, including Connecticut and other northeastern states. Infection rates of West Nile Virus and other mosquito-borne diseases are likely to rise, over the long term, as a warming climate creates more favorable habitats for mosquitoes. Connecticut is expected to get warmer and wetter over the coming century, enhancing mosquito populations by creating more suitable habitat. Additional information about mosquito management in Connecticut can be found on Department of Energy and Environmental Protection’s (DEEP) website or the Connecticut Agricultural Experiment Station (CAES) - portal.ct.gov/CAES.
Emerald Ash Borer

It is assumed that the emerald ash borer (EAB), which attacks ash trees almost exclusively, is now present in every town in the state. Emerald Ash BorerIn Connecticut, ash trees made up just slightly less than three percent of the trees in the forest, most of which are white ash. However, the loss of ash trees in a forest stand also reduces vital habitat and allows undesirable invasive plants to fill the gaps that are created. Movement of ash, in particular as firewood, nursery stock, logs and wood packaging materials, has been cited as the most likely means by which EAB has spread so rapidly.69 Because EAB is already considered as established in North America, eradication is no longer a goal. Instead, focus is on slowing or preventing the spread of the insect into new areas while managing and reducing its numbers in places where it is already found. Biological controls, such as parasitoid wasps, were released in the Northeast United States, including Connecticut (2013), as a biological control for EAB. Intensive research has shown that these parasitoids have established in the locations they were released and have successfully spread from those locations. It seems probable that the parasitoids will be able to suppress EAB populations to levels that will allow ash to regenerate in our forests; however, the longer term success of such control measures is unknown.70 Additional information about the EAB in Connecticut can be found on DEEP’s website or CAES - portal.ct.gov/CAES.



The highly invasive aquatic plant, Hydrilla verticillata, known commonly as 'hydrilla' or 'water thyme' was first detected image of CT River hydrilla from USACOEin the Connecticut River in 2016 around Glastonbury, Connecticut and has since spread into the river’s many coves, tributaries, and boat basins. Hydrilla is an aquatic plant that has earned the title “world’s worst invasive aquatic plant”. The United States Army Corps of Engineers (USACE), New England District and the Engineer Research and Development Center (ERDC) will lead a demonstration project to determine the effectiveness of registered herbicides to safely reduce and control the spread of the Connecticut River hydrilla. Research on hydrilla’s growth patterns, water exchange dynamics in the Connecticut River, and herbicide efficacy in laboratory conditions began in 2023 to guide operational scale field demonstrations of herbicide efficacy in 2024. The USACE is working in partnership with the Lower Connecticut River Valley Council of Governments and the CAES. To control and eradicate hydrilla, the USACE and ERDC plan to treat several sites on the Connecticut River during the summer of 2024.71 Additional information about the hydrilla in Connecticut can be found on the CAES website - portal.ct.gov/caes/oais/connecticut-river-project.


Jumping Worms

Jumping worms, also called crazy worms and crazy snake worms, are noticeably fast-moving, highly active worms with a strong, rigid, Image of jumping worm on ground provided by the USDA Forest Servicemuscular body that can thrash violently when disturbed. Jumping worms are an invasive species that alter the composition of the topsoil which leads to an increase in nutrient leaching, erosion,  drought vulnerability, turf detachment, root desiccation, and low germination. Jumping worms are established in Midwestern states and are currently spreading throughout New England. Jumping worms are primarily spread in soil, mulch (a principal means of distribution), compost, and yard waste.72 Additional information about the jumping worms in Connecticut can be found on the CAES website - portal.ct.gov/CAES.


Technical Note: *Collection data for mosquitoes for 2016-2018 has been modified from previous reports because of the introduction of new data from a trapping site in Bridgeport. Information on other invasive species can be found in the Council’s 2022 special report "INVASIVES": PREVIOUSLY DESCRIBED and NEWLY ARRIVED.


68  Connecticut Agricultural Experiment Station (CAES); personal communication from J. Shepard, December 14, 2023.

69  DEEP, Connecticut’s 2020 Forest Action Plan, December 2020; portal.ct.gov/-/media/DEEP/forestry/2020-Approved-CT-Forest-Action-Plan.pdf.

70  Emerald Ash Borer Network, Biological Control; www.emeraldashborer.info/biological-control. Rutledge, Claire, Connecticut Agricultural Experiment Station, “History and Current Status of Emerald Ash Borer in Connecticut, personal communication April 3, 2024.

71 United States Army Corps of Engineers, New England District Website, Connecticut River Hydrilla, accessed 3-8-2024; www.nae.usace.army.mil/Missions/Projects-Topics/Connecticut-River-Hydrilla/.

72  Ridge, Gale E., Connecticut Agricultural Experiment Station (CAES), Jumping Worms (Megascolecidae: Pheretima) in Connecticut, September 28, 2023; portal.ct.gov/-/media/CAES/DOCUMENTS/Publications/Fact_Sheets/Entomology/Jumping-worms-in-Connecticut.pdf.