Late last summer, I hiked the Beehunter trail with friends. It was weird and creepy. When we stopped, it sounded like it was raining. The trail was littered with bits of leaves – like the schnitzels of paper after children have been practicing with scissors. Normally, when you look up into a tree, you can see distinctive leaf shapes and recognize which trees are maples or oaks. Not on this day. The leaf shapes had been altered.
What sounded like rain was frass – caterpillar poop – falling on the leaves. And it was these very same caterpillars responsible for the misshapen leaves and leaf fragments on the ground.
During subsequent hikes, I also noticed a high density of egg masses on the trees – far more than normal. Normal. Ha. Before 1869 normal would be zero.
Brought here by Étienne Léopold Trouvelot from Europe to Massachusettes with the intent of breeding a more robust silk worm, the Gypsy moth caterpillar escaped the laboratory and became a part of the northeast landscape. Over the years, it has managed to spread as far west as Wisconsin, north into Canada, and south to Virginia or North Carolina.
Gypsy Moths overwinter as egg masses. In spring – late April and into May, the caterpillars emerge and begin eating. By late June or early July, they will reach their final instar and pupate. About two weeks after pupation, the adults emerge.
Left: Female laying eggs by Jeff Tome. Right: Male by Jenn Orth
Females are flightless. Males will find the females by “smelling” pheromones with their large, feathery antennae. After mating, the female lays approximately 500 eggs. Because the female is flightless, the egg masses are found on trunks along with empty cocoons.
Gypsy Moth caterpillars will dine on over 500 species of tree leaves, both deciduous and evergreen. A serious infestation can defoliate a forest affecting the trees’ mortality. The New York State Park system defines an infestation as serious enough to treat when there are 1,000 or more egg masses per acre. Last fall, teams surveyed the trees in high use areas of the park and found an AVERAGE of 5,700 per acre with some areas having in excess of 14,000 masses per acre. Concern in these high use areas is for visitor experience in the park. Camping and hiking is unpleasant when frass falls into your food, or you slip on caterpillars as you walk. Yes, they are that plentiful in some places!
Egg masses and empty cocoons – by John B.
Of bigger concern to me is impact on the ecosystems, in particular the old growth areas of the park. Survey teams in the these areas found densities of egg masses ranging from 1,990 to 16,430 per acre. It would be such a shame to see the huge old hemlocks affected by these voracious caterpillars, which will devour hemlock needles in their later instars.
To combat the infestation, the park is spraying Gypchek – a virus that targets the gypsy moth species, but is reportedly harmless to humans, pets, and other species of wildlife. One dose was applied last week. Another will be applied sometime this week.
I haven’t been to the park yet this spring. I’m a little nervous about it. Guess I’ll know soon enough when I attend the Allegany Nature Pilgrimage!
I found these files on the internet: