RLHT Takes on Three Invasive and Nuisance Species

Wall LettuceRusty Crayfish Spruce Budworm Larvae

Rangeley, ME - In line with our mission to maintain the integrity of our natural resources, the Rangeley Lakes Heritage Trust is focusing its efforts this summer on halting the spread of two invasive and one nuisance species: wall lettuce (Mycelis muralis), the rusty crayfish (Ornectes rusticus), and the spruce budworm moth (Choristoneura).

Wall lettuce is an invasive flowering plant related to the dandelion that can be identified by a triangular leaf tip larger than its other leaf lobes, its straight, two to three foot tall stem, and its small, yellow, five-petal flowers with ragged edges. Native to Europe, it thrives across North America; while it is best adapted to shady, damp, and disturbed land. Wall lettuce can also thrive in full sunlight and under drier conditions. This plant produces many seeds that are distributed by wind much as dandelions do, with a small cluster can produce hundreds of offspring. These plants can choke out our native flora by outcompeting them for sunlight, water, and soil. RLHT staff is surveying land under our management for wall lettuce, mapping its present, and pulling up any plants found.

The rusty crayfish is an aquatic invasive species introduced to our waters via out-of-state bait buckets. It can be identified by its large size, a rust-colored spot on each side of its carapace and, most distinctively, an oval-shaped gap in the claw when it is closed. It is aggressive, and not only competes with native aquatic species for resources, but preys on them as well. RLHT is working in conjunction with the Volunteer Lake Monitoring Program and University of Southern Maine’s Dr. Wilson to trap and identify  crayfish from lakes, ponds, and stream in the Rangeley Lakes region. This project is part of an ongoing effort to gain a clear picture of crayfish populations across our state and to determine how far the invasive rusty crayfish has spread in Maine.

Native to Maine but harmful to our forests is the spruce budworm. The adult moths of this species lay their eggs on the underside of fir or spruce needles, with an individual laying up to 200 eggs a year. The larvae feed on spruce, fir, and even larch and hemlock needles, and a tree can be completely defoliated by this species in two years. While their population varies from year to year, it has been found that a population boom occurs about once every 35 years. The destruction caused by the sheer number of larvae hatched during a spike in their numbers reduces forest value and increases the risk of forest fires. In partnership with Maine’s Department of Agriculture, Conservation, and Forestry (DACF), RLHT will be setting traps baited with pheromones to catch and kill spruce budworm moths. These traps will then be sent to DACF to help this agency track population growth trends and predict the next large-scale infestation.

As always, the RLHT’s greatest resource in helping fight the spread of invasive species is you. We ask that you make sure any plants you introduce to your garden are not invasive, that you pull up any wall lettuce you may come across, and that you check your boat and bait buckets for invasive hitchhikers before you put in.