They’re back — reports are in from all over Ulster County that hordes of tiny, black caterpillars, the first stage of a spongy moth outbreak are dropping off houses, trees, garages and setting off intense itching, hives, welts and red blotches on people who are sensitive to the teensy insects.

The only effective response is to avoid getting showered with them. Not so easy when there are thousands lowering themselves off your house or trees. No one is immune from this.

If you are seeing hordes of tiny black caterpillars, then, unfortunately, you know it’s too late. The best opportunity to destroy that horde was when the “spongy” egg masses were laid last August. A strict appraisal of a house and property can reveal where the egg masses were laid. They look like brown smudges of mush; when you tackle them use a rag and a bucket of hot water. They wipe off and go into the bucket and the heat kills them. Dispose of water and eggs onto the compost pile.

But once they’ve hatched, they’re back. You can kill a lot of them, but there are so many that some are sure to survive.

The spongy moth, Lymantria dispar dispar, is an invasive insect that came from France in 1869. It was introduced as an accidental byproduct of an effort to crossbreed them with silkworm moths, of which there was a shortage at the time. They didn’t crossbreed and instead some escaped into the wild and were soon established around Medford, Massachusetts. From there, they spread widely and have become a notable nuisance. They currently infest forests in all East Coast states from Maine to North Carolina. They have also invaded the Midwest and caused problems in Michigan and Wisconsin.

“Although thousands of acres of trees can be damaged, spongy moths do not pose a major threat to New York's forests overall,” the state Department of Environmental Conservation reports. “Deciduous trees (trees that lose their leaves each fall) can regrow a new set of leaves by July and can usually withstand 2-3 successive years of defoliation (removal of leaves) without being killed. However, spongy moth can impact the health of individual trees.”

With the eruption of millions of the caterpillars, it’s pretty likely that this will be tough year for our oaks and apple trees. Those are the preferred hosts for these caterpillars. The DEC notes that they will avoid ash, yellow poplar, sycamore, black walnut, catalpa, locust and American holly, and shrubs such as mountain laurel, rhododendron and arborvitae. Of course there are very few ash trees left, since they were annihilated by the invasive emerald green ash borer a few years back.

When the caterpillars are bigger and if they run low on oak leaves, they will switch to eating conifer needles. Conifers are more easily damaged by defoliation. But all trees that are stripped of their leaves by the spongy moths will become vulnerable to other pests and diseases.

For now, avoid contact with them. Sweep them off your house and bury them in a pile, if at all possible.

The DEC recommends use of Btk, a natural bacterial spray to eliminate spongy moths on garden trees. The agency states “biopesticides are made from naturally occurring bacteria, viruses, fungi, or protozoans that can be targeted to a specific pest. The most common of these is Bacillus thuringiensis (Bt), which occurs naturally in soil and on plants. The Bt subspecies kurstaki (Btk) is the most appropriate to use for spongy moth control.”

The DEC goes on to say, “Btk works best on young caterpillars, which become more resistant to treatment as they mature. When Btk is eaten, the caterpillar becomes paralyzed, stops feeding, and dies of starvation. Btk is harmless to people, animals and plants, but does affect other young moth and butterfly larvae. Proper application will help limit exposure to non-spongy larvae.”

The agency also issued a warning: “Please note that all of these options may protect individual trees or small areas, but they will not erase a local spongy moth population now or in future years. In large forested areas, manual removal is often not practical during an outbreak.”

The DEC does not manage the spongy moth, and treatments are usually limited to ecologically or culturally significant forests. The DEC does not provide funding for controlling spongy moths on private property.

Still, never forget that nature is full of predators that will take a toll, including birds, rodents and parasites. But besides that incidental culling, what really controls the moths is a combination of a virus and a fungus. First is a nuclear polyhedrosis virus which is endemic among the moths and sets off mass infections when the numbers of the caterpillars reach a certain saturation level. Adding to that death toll will be more, caused by the fungus, Entomophaga maimaiga.

Caterpillars killed by the virus will hang from branches and bark and then liquefy, producing a foul odor.

With the appearance of so many spongy moth larvae at this point in the season, it’s a fair bet that here in our area we are in for another year of defoliation. The best hope is that the virus will spread and kill off enough of the caterpillars to end the outbreak.

If you want to limit the effects in your own garden and area, you can purchase lures usually sold as “gypsy moth lures” using the old non-scientific name for these pests. Usually housed in a plastic tube which you fill with soapy water, they attract the male moths with a small pheromone patch. The tubes have to be emptied frequently during peak moth flight times, a moderately disgusting task.

Combine that with careful examination of your trees and buildings. The female moths do not fly. They crawl to a good spot and emit the pheromone to attract the males. Later, they will lay the “spongy” egg masses. If you find those and destroy them, along with the white females, you may prevent further infestation the following year.