As reported in this column in March, “To Spray or Not To Spray,” winter moths were expected to expand along the Seekonk River and in Blackstone Park this year, but no one knew how serious the infestation would be. Now we know—it’s serious.
In early May tiny bright green caterpillars softly plopping onto the heads and shoulders of volunteers working in the Blackstone Park Conservation District signaled a major attack on Providence trees by the winter moth. Barely a centimeter long though they can reach an inch, and no thicker than thin string, the caterpillars appeared harmless, but they were not. Perforated spring leaves in the trees above testified to their appetites.
First eating buds from the inside out, then swinging from tree to tree on long silken threads to take more bites, the caterpillars made short work of many leaves before they vanished into the next phase of their cycle as pupae in the ground. In Providence the woodlands of Blackstone Park and Neutaconkanut Hill and nearby street trees were hit hardest, probably tempting the moths with “all that food” in one place, said City Forester Doug Still. A neighbor on Paterson Street found his oak trees stripped bare. The pest was an equal opportunity destroyer, going after the normally untouchable Norway maples, the invasive trees that cause so much harm to other flora.
With few exceptions, the Boulevard was spared this year but for a weeping cherry that was defoliated. Trees in this predicament will normally send out a second set of leaves.
Nothing can be done about the moths this season, says Still, but next winter it will be possible for homeowners to spray individual trees though even the most harmless known sprays can kill bees. Spraying the woodlands however, will not be possible.
The eventual hope for woodland trees, aside from birds or the arrival of another natural predator, may be the parasitic fly cyzenis albicans, which wasfirst introduced to Rhode Island at Goddard Park in 2011 by the University of Rhode Island (URI). More flies were released in Bristol and Jamestown in 2013, and in Cumberland, Kingstown and Jamestown in 2014.
Botanist Heather Faubert, research assistant in the Department of Plant Sciences at URI, who is managing winter moth bio-control in Rhode Island, speculates that the fly, which is present in Seekonk, may eventually spread to Providence. The success of this method of control in Nova Scotia and Massachusetts without unwanted collateral damage is encouraging, but takes time.
Jane Peterson
