Here’s Why You Need To Be Aware of the LDD Moth This Spring
The name may have changed but the damage it does to trees remains the same. The LDD (or European spongy moth) is not one to be ignored. Here's why.
The LDD (Lymantria dispar dispar), or spongy moth, is an insect to be taken seriously. You may know it by its former name of “gypsy” moth, which was abandoned in 2021 because of its offensive connotation. The Entomological Society of America’s Better Common Names Project, which works to address problematic insect names, recommended the change.
Although the name may be different, this insect’s ability to injure trees remains intact and worrisome, says Kirby C. Stafford III, Ph.D., chief scientist and state entomologist at the Connecticut Agricultural Experiment Station (CAES).
If you’re a homeowner with trees, here’s what you should know.
What Is an LDD Moth?
The LDD or spongy moth is a non-native, invasive forest pest first reported in Massachusetts in the late 1800s. In the caterpillar stage, its larvae feed voraciously on the leaves of more than 300 species of deciduous and evergreen trees and shrubs.
Each year, from late April to early May, a new generation of LDD moths hatch from clusters of eggs laid the summer before. The emerging hungry and destructive caterpillars infamously chow down on the developing leaves of plants and trees, stripping them of their foliage at an alarming rate.
What Do LDD Moths Look Like?
The flightless female moth is white, sometimes with small black markings, with an average wingspan of about 1-1/2- to two inches. She deposits fuzzy, teardrop-shaped egg masses in tree bark, as well as along fence posts, brick walls, outdoor furniture and wood piles.
The flying, but much smaller male spongy moth, is brown and measures about 1-1/2-inches long.
Larvae, when fully developed, are brownish with five pair of blue dots, followed by six pair of red dots lining the back. Yellow and brown hairs stick out from their sides. The caterpillars grow to be about a quarter of an inch long.
What Do LDD Moths Eat?
The spongy moth caterpillars (larvae) eat young and tender foliage on various shrubs and trees. Although they prefer munching on oak and aspen trees, it’s not uncommon to find them in apple, birch, poplar and willow trees. They’ve also been known to dine on evergreen species including pine, spruce and hemlock.
Stafford says the LDD moth’s larval stage run about 40 days. While LDD caterpillars often seek shady spots during the day, if there’s an outbreak and populations are dense, they can feed continuously day and night.
“The caterpillars complete their feeding sometime during late June to early July and often seek a protected place to pupate and transform into a moth in about 10 to 14 days,” Stafford says.
Then the generational moth cycle begins again.
Where Do LDD Moths Live?
From its original North American position in Massachusetts, the spongy moth migrated south to Virginia and north to the Canadian Maritime Provinces. Its current invasion front now stretches from North Carolina to the eastern part of Minnesota.
What Damage Do LDD Moths Cause?
These moths and their larvae are small, but the damage they cause is considerable.
Direct tree damage
The LDD moth does the most harm to trees by defoliation (the removal of leaves). Most healthy trees, particularly those that lose their leaves, can withstand this sort of attack for one season. However, if outbreaks occur in successive years, it could leave all trees weakened and susceptible to stresses like diseases, drought and injury from other pests.
The Invasive Species Centre estimates hundreds of millions of dollars in damage occur from the LDD moth in the U.S. annually.
The indirect economic impact, in the form of expense to homeowners, is hard to measure. It could include increased timber value, pest control treatments, removal and replacement of weak or dead trees, and yard cleanup costs.
“The spongy moth caterpillars can also be a problem because they drop leaf fragments and frass (droppings) while feeding, onto decks, patios, outdoor furniture, cars and driveways, leaving a mess,” Stafford says.
How To Get Rid of LDD Moths
According to the CAES, here’s what homeowners can do to get rid of spongy moths in infected trees:
- Scrape off egg masses and destroy them in soapy water.
- Wrap burlap or sticky barrier bands around tree trunks to block caterpillars from climbing up into trees to feed at night.
- Hire a licensed arborist to spray larger trees in early to mid-May with Bacillus thuringiensis var. kurstaki (Btk), a biopesticide (AKA native microbe) that specifically targets caterpillars/larvae when ingested. It does not work against the pupa and adult spongy moth, nor is it toxic to other non-targeted insects.
How To Prevent LDD Moths From Invading Trees
There’s not much homeowners can do to prevent the moth from attacking trees. However, during an outbreak in 1989, CAES scientists discovered an entomopathogenic fungus called Entomophaga maimaiga was killing caterpillars. Since then, the fungus has been the most important agent suppressing spongy moth activity.
“The fungus occurs naturally and requires rains at the appropriate time in late spring and early summer for germination and infection of the caterpillars,” says Stafford. However, this method is not 100 percent effective. “The fungus cannot prevent all outbreaks, mainly during drought, and hot spots in some areas continue to be reported,” he says.
The best you can hope for is well-timed rain.