If your house is covered with small pale moths near your porchlights at this time of year, then you have a wintermoth population.
The wintermoth, which so many of you know by the little green inchworm caterpillars that eat your trees in the springtime, is now in its “adult form”. They ended their pupation about 2 weeks ago, and are now mating. Pupation occurs from early June, when the larval caterpillars drop from the trees and bury themselves in the soil, until this time of year. The moth itself is not harmful to your landscape, but their conspicuous presence at night is unmistakable.
This is a time of year where a “”do-it-yourself”” control can have some impact; the female moth is flightless, and must walk up the tree trunk to lay her eggs. You can trap her and prevent her brood from becoming the springtime nuisance by applying an effective bug barrier on your susceptible trees. This is accomplished by creating a solid, impenetrable barrier encircling the tree trunk- there are a few commercially available products at your local garden center or hardware store. To make the barrier most effective, apply a sticky substance to the barrier so the moth cannot move. One commonly available product is called tanglefoot. I have also seen some people use duct tape effectively as well. You will need to check your sticky barrier regularly too- if populations are high enough, you may need to reapply your sticker as the moths accumulate.
This will not be the answer to all your problems if you have had a significant wintermoth population in the past, but may be able to reduce populations a little bit. Foliar sprays still offer the best value and control for most landscape situations, but also emerging are microinjections. While this type of treatment may cost a bit more, it offers you the opportunity to address the problem in the fall, providing a better level of control in the spring. This is a great option for clients that are sensitive to chemicals, or have sensitive landscape areas such as vegetable gardens or koi ponds.
One last thing to remember, if you are looking for do-it-yourself options, be sure to select a product labelled for control of caterpillars, or lepidoptera. I have seen many people buy the wrong products at a garden center- always read the label! Products like horticultural oil will not control caterpillars once they have hatched. If you need to consult an arborist, we at Mayer Tree are always available to assist you.