Photo of Swallowwort by Chris Evans, Illinois Wildlife Action Plan, Bugwood.org
Last spring the Maine Forest Service launched a program aimed at tackling invasive plants in woodlots across the state, and particularly here in central and coastal Maine. I joined 40 foresters and natural resource professionals for a three-day training to hone invasive plant identification, discuss treatment strategies, and prepare plans to help landowners understand and treat their invasive pests.
Within ecology and forestry, a plant is considered invasive if it is both non-native and causes economic or ecological damage. In forestry, we worry most about aggressive growth limiting tree regeneration, though by the time an infestation reaches that point it has likely choked out native herbs and shrubs, lowering habitat and forage quality, and altering many of the relationships and processes in our forests. Though we all benefit from healthy forests, combating invasives mostly falls to private landowners, with only limited programs to help with the expense.
Fortunately the MFS program may help fill this gap. However in this initial year, I would not describe the process as simple. ‘We are building this plane as we fly’ was the most common response to our questions. Regardless, in preparing seven plans, I waded through thickets of bittersweet and honeysuckle and cursed the sharp multiflora rose thorns. The MFS provided cost-share funding for the preparation of these plans, which now make the landowners eligible to apply for free treatment by the MFS this coming summer. Their treatment priorities will focus on those species most troubling, like livestock-toxic black swallow-wort, but will likely also attack species at the edge of their current infestations to help stop their spread.
So despite the program’s confusing deadlines and limited advertising, landowners expressed strong interest, which highlights the need for more and creative ways of supporting them as they battle invasive plants. There has been no word as to whether this program will be extended, as managers were only able to secure this one year of initial funding.
MOTHS – BROWN-TAIL AND LYMANTRIA
I thought ticks were the bane of my professional existence, but this summer I met my true nemesis – the brown-tail moth. It was one of the many excessively hot days and I was heading into the woods in a t-shirt when the landowner mentioned they had brown-tail. We glanced at the denuded oaks and grabbed long sleeves. Half an hour later I was scratching my arms and struggling to collect good data and keep the caterpillars off me and our equipment. Their hairs, as many of you know, cause painful skin rashes and even respiratory problems. Though they defoliated along the midcoast for a number of years, their irritating and destructive ways moved inland and eastward this spring. When the moths began defoliating oaks and dispersing harmful hairs in Waterville the local Morning-Sentinel ran nearly daily stories about the invader; the city has already appropriated funds to help monitor and destroy the webs of many of the overwintering moths. These are indeed, unwanted pests. But there is another way. When we returned to finish the project a few weeks later, the landowner handed me a head-to-toe tyvek suit – I sweltered, but didn’t itch.
The brown-tail moth is only one of two non-native, invasive moths threatening our forests this year. Lymantria dispar, which many of you know as the Gypsy moth, is also rapidly spreading. This summer, the Entomological Society of America announced it would change the common name to remove the use of an ethnic slur, though they haven’t announced a new name; I’ll refer to it as Lymantria.
Lymantria and brown-tail prefer oak and are capable of severe defoliation. Lymantria, however, are slightly less particular and will attack just about any hardwood, and even softwoods, where oaks are not abundant. Both moths can turn a whole hillside brown in the middle of summer, as easily witnessed along Route 5 through Stoneham and Lovell. Later, I came upon them as far east as Canton and north into Bethel. As with most hardwoods, oaks can withstand a year or two of pretty severe defoliation, for after the caterpillars’ mid-summer pupation the trees re-leaf to a degree. That limited late-summer photosynthesis can help restore some of the energy necessary for tree functions, and can be repeated in successive years, if necessary, though severe infestations can cause widespread mortality. Fortunately, most trees generally recover.
Both moths arrived in Massachusetts in the late 1800s and quickly began spreading. Brown-tail settled down after an initial wave, and until recently, remained localized to populations in Cape Cod, Massachusetts and Midcoast Maine. Lymantria populations generally remain low but periodically explode, remaining high for several years before starvation, disease, and predators knock the population back again. Wet spring weather favors fungi that attack the caterpillars.
Unfortunately, without natural allies there is little we can do to control these two pests. Brown-tail moth webs within reach can be cut and burned or killed in a bucket of soapy water and the brown egg masses of Lymantria can be scraped off and destroyed in the same way. Individual trees may be protected with pesticides.
Another option that appeared in an early 1900s publication on the brown-tail moth suggests using three to four pounds of arsenate of lead in 50 gallons of water, applied when trees just leaf out and caterpillars are small. If caterpillars get too big, they should be knocked from the tree by vigorous shaking and wetted with a kerosene emulsion once on the ground1. This book is full of fascinating history and first hand accounts of the early infestation and is well worth your time if you can’t sleep for the itch. But if you find yourself wondering if lead and arsenic are actually that harmful, it may be time to contact your doctor.