​Combating the Elevated 2020 Gypsy Moth Population

Gypsy Moths

​Combating the Elevated 2020 Gypsy Moth Population

Spongy Moths (Gypsy Moths)


Renaming Gypsy Moth to Spongy Moth
A pest that has been defoliating our forests now has a new common name. T he Entomological Society of America has renamed Lymantria dispar (formally known as ‘gypsy moth’) the spongy moth.The Entomological Society of America recognized the need for a change in the common name in July of 2021 as the previous name contained an ethnic slur.

The new common name announced in March of 2022, refers to the insect’s light brown, fuzzy egg masses that resemble sponges. Also, the countries of France, Germany and Turkey reference sponges in their common name for Lymantria dispar.

In the early 20th century common insect names, versus the scientific name, were adopted to help bridge communication between those who study insects (entomologists) and those who don’t. Entomologists are always striving for effective communication to help advance the science of entomology and provide information to the public and policy makers.

About 25 percent of the US population claim they have a fear of insects. Yet, insects play a significant role in the health of our planet. For example, some insects act as pollinators while others are decomposers breaking down wastes such as dead animals and plants. Without insects, plants would not be able to reproduce and dead things would accumulate in the environment.

Not all insects are beneficial to the environment they inhabit, especially if they have been introduced accidentally or intentionally. The spongy moth is an example if an introduced insect as it is not native to the United States. They were brought from France in the late 1860’s with the intent of developing a silk industry in the US. The experiment was not successful with some moths escaping. By 1981 these destructive moths were found throughout New York State.

It is not the adult moth that causes the damage but the larvae (caterpillars) that hatch from overwintering egg cases in April and May. Once hatched the larvae begin eating the emerging young leaves of many tree species. The early damage from the tiny caterpillars often goes unnoticed. Once the caterpillars are close to an inch in length their appetites increase and their feeding becomes visible with thinning tree canopies. The caterpillars will grow to 2 inches.

Areas of central and western New York have experienced heavy defoliation the past two years. Spongy moth populations will remain low for a number of years and then for some yet to be explained reason the population skyrockets. Most outbreaks last two to four years. When populations are high there are an estimated one million caterpillars per acre in some forests. While a year or two of defoliation will not kill hardwood trees there is a decrease in leaf surface area and overtime the trees become stressed.

Finding and removing the egg masses provides the easiest control. When identified the egg mass can be carefully scraped off using a putty knife and dropped into a container with dish soap and water. Allow the egg masses to remain in the soapy water for two days. Just scraping them onto the ground and stepping on them does not kill them.

Avoid damaging the tree bark. Several people have called and said they used a flame to burn the egg masses. While this kills the eggs it also damages the vascular system of the tree which is just below the bark. Damage from this inappropriate egg mass removal may kill the tree faster than the larvae feeding.

The larvae are hatching now. NYSDEC’s website has a link to sampling protocol to help determine the potential for a large outbreak or if an insecticide spray is warranted on smaller larvae. Spraying can be expensive and timing of the spray is critical. There is evidence that larvae are controlled naturally by birds, rodents, parasites and disease.

The larvae mature in approximately 7 weeks. At maturity, they can eat approximately one square foot of leaf surface in a single day. Once mature they go into a cocoon and emerge July into August as adult moths. As they mate, the female lays eggs which overwinter and the cycle starts over.

If you have trees that have experienced defoliation from spongy moth, be on the lookout for the hatching larvae. Also check firewood, dead trees and even leaf litter as the female moth lays eggs there as well. Cornell University Insect Diagnostic Laboratory website has more on the management and control of this pest. Please contact Cornell Cooperative Extension of Cayuga County at 315-255-1183 with questions about this devasting pest.

*This article was originally printed in the Citizen newspaper on April 15, 2022 by Judy Wright


Last updated June 29, 2022