Spongy moth is the new common name for Lymantria dispar, formally known as the gypsy moth. Read more at: Spongy Moth is the New Name for an Old Pest

This year, we saw severe tree defoliation across the country, most notable in oak and beech trees throughout New England. We also saw messy patios, furniture, and outdoor living areas, and in some cases, even unexplained red, itchy rashes. The culprit? Spongy Moth.

In the last few years, the Spongy Moth population in New England has expanded rapidly, and one of the clearest correlations has been the weather. Because we had an unusually dry May, the parasitic fungi and viruses that usually keep this pest in check were suppressed. This allowed most of the larvae to escape, attack, survive, and defoliate trees.

Research has shown that four consecutive years of defoliation can ultimately lead to tree mortality. This means Spongy Moth must be stopped now, or we could be subject to irreparable damage to our landscapes. If we experience continued spring and summer drought in 2018, we can expect populations to build, and to spread, encompassing more acres and cites.

First, let’s go over how Spongy Moth came to be. This will help us best understand how to fight it.

Introducing: The Invasive Spongy Moth

Spongy Moth (Lymantria dispar) was introduced to the U.S. in New England in the 1800s in an attempt to manufacture silk. It subsequently escaped, and has caused damage to our forests and urban trees ever since. The damage this year rivals that which occurred in the early 1980s – many trees were completely defoliated. Boston.com reports the Bay State alone suffered more than 350,000 acres of defoliation from the caterpillars in 2016, compared to about 38,175 the previous year. The exact damage from 2017 is still unknown, but it is expected to be the worst year since 1981.

The current expansion of Spongy Moth destruction is largely due to the prolonged, dry springs over the last two years, preventing natural diseases from controlling the pests. While predators help, fungi and viruses are generally needed to keep Spongy Moth in check and reduce explosive growth.

Flightless female moths mate and lay eggs on the underside of tree branches in July. This tan egg mass can contain hundreds of eggs. Eggs hatch in late April and May, and Spongy Moth larvae begin to feed on newly emerging tree leaves. These young larvae may blow between trees on silken threads, greatly expanding their distribution and damage. As larvae reach maturity after two months of feeding, they pupate, and adult moths emerge, completing the life cycle. Trees that are completely defoliated may re-foliate 3 to 4 weeks after feeding ends, expending an enormous amount of energy. Repeated defoliations may kill trees or severely weaken them, exposing them to native secondary disease or insect organisms.

Spongy Moth larvae feed on several types of trees, and under high population pressure they will feed on almost any tree or shrub. Their preferred species include oaks, maple, beech, birch, hawthorn, apple, poplar, and willow. Mature larvae may even feed on hemlock, spruce, and pine as well. In addition to severe defoliation damage, their droppings cover everything.

Don’t Let It Happen Again … Here’s What You Can Do

We recommend planning your treatment now to eliminate pest damage next spring. You can begin treating after the winter is over as soon as uptake conditions are favorable, but we suggest no later than May. Typical Spongy Moth hatch begins anywhere from late April to Mid-May depending on temperature, precipitation, and soil temperatures. Treatment should be completed as the caterpillars increase in size to minimize feeding damage.

Trunk injection with TREE-äge® or TREE-äge® G4 provides both preventative and curative control depending on the time of year treatment is applied. TREE-äge provides control for a minimum of a year, and potentially up to two years. Treatment with TREE-äge or TREE-äge G4 protects your trees from Spongy Moth and up to 51 other types of pests, including Emerald Ash Borer and Winter Moth.

Taking proper preventative measures now to combat Spongy Moth could be the difference between your trees living or dying. Connect with your Arborjet Regional Technical Manager or service provider today to start the conversation and explore your options.