I witnessed the first adult male winter moths (Operophtera brumata) on my white panel screen back door over the Thanksgiving holiday. They were there two nights in a row obviously attracted to the outdoor security light that I leave on in the early evening. The male moths are light brown to tan in color and all four wings are fringed with small elongate scales that give the hind margins a hairy or fringed appearance (see photo 1). The male moths emerge (the adult stage of winter moth) from the soil usually in late November and may be active into January whenever the air temperatures are mild (usually above freezing).

The female moth is gray, almost wingless and, therefore, cannot fly (see photo 2). She emits a sex pheromone that attracts the male moths. Females can usually be seen on the trunks of trees. After mating, the females lay their eggs in bark crevices, under lichen, or on other areas of the trunk.

The larvae (small green caterpillars) hatch from eggs just before bud break from late March into mid-­‐ April. The small green caterpillars (photo 3) feed on both flower and foliar buds of many deciduous species including maples, oaks, ash, apples, crabapples, blueberry cherries and lindens. As the history of this invasive pest has shown, it doesn't take long for a medium to large size population of the winter moth caterpillars to defoliate a mature tree. The winter moth population is definitely on the rise in Rhode Island, so home-­‐owners should be on the lookout for this foliage-­‐eating pest in 2012.

The following are just some of the measures that can be taken by property owners to protect their plants.

• Apply a dormant oil spray to the trunk and branches of trees to kill the overwintering eggs before they hatch.
• Apply the bacterium Bacillus thuringiensis (known as Bt) to the leaves as the young caterpillars are feeding on the emerging leaves.
• Apply Spinosad (bio-­‐rational compound) to the leaves at the first signs of winter moth damage. Unfortunately, Spinosad is highly toxic to honey-­‐bees so do not apply when crabapples or other flowering trees are in bloom. The good news is that once the application of Spinosad has dried, the threat to bees drops significantly. The homeowner can purchase Spinosad under the trade names "Bulls Eye Bio-­‐ Insecticide and "Monterey Garden Insect Spray".
• Apply Tebufenozide (trade name "Confirm") to the leaves as they emerge in spring. This product is an insect growth regulator and kills caterpillars by arresting their developing into adult moths. It is only available to licensed pesticide applicators. It is also toxic to bees and should be used with caution.


Finally, there are several chemical insecticides such as Carbaryl (e.g. Sevin) and Malathion that can be used against winter moth. Many of the Pyrethrums are also labeled for caterpillars on deciduous plants. These products while very effective come with several environmental risks. All are toxic to bees and all are known to reduce the populations of beneficial organisms as well as the target pests. Last, but not least, RITree urges everyone to always read, understand and follow all label directions on pesticide products. Also, when in doubt, please consult with a certified arborist for help in developing the best strategy for protecting your plants against harmful pests.