Q: I live in Berkshire County, MA and Lymantria dispar caterpillars were everywhere in my yard! What should I do to protect my trees and shrubs?
The Entomological Society of America has announced that it is undertaking an effort to remove offensive and derogatory language from insect common names.This includes the common name for the insect formerly known as gypsy moth (Lymantria dispar) and others. Replacing offensive names is consistent with the values of the University of Massachusetts with regard to diversity and inclusion. UMass Extension is working on removing this terminology from our online resources and reporting, but warn that some archival materials may continue to include such language. For more information, visit: https://www.entsoc.org/entomological-society-america-discontinues-use-gypsy-moth-ant-names.
A: The caterpillar stage of the non-native moth, Lymantria dispar, has reportedly been very active and noticeable in certain parts of Berkshire County, Massachusetts in 2021. Reports have come in to UMass Extension from Alford, Great Barrington, Richmond, South Egremont, and Williamstown. This has come as a bit of a shock for some people living in these areas, as they were fortunate enough to be almost entirely spared during the peak of the most recent outbreak in other parts of eastern, central, and western Massachusetts in 2017 when 923,000 acres were defoliated in those locations, most of which were outside of Berkshire County. There are additional reports of noticeable Lymantria dispar activity in other parts of New England at this time, including but not limited to certain sections of: Connecticut, New Hampshire, and Vermont, as well as parts of New York.
Unfortunately, once L. dispar caterpillars reach a certain size, they are quite robust and very difficult to manage. This often corresponds with when they are most noticeable to us, and when defoliation from their feeding is most visible (and nearly complete for the current season). The good news is: caterpillars typically begin to pupate by the third week in June in Massachusetts, and adult moths may be seen by the end of June or the beginning of July. Once pupation occurs, feeding from Lymantria dispar stops for the current year. (Only the caterpillar stage feeds on the leaves of its host plants, which include but are not limited to: oak, poplar, willow, birch, witch hazel, blueberry, and many other deciduous trees and shrubs. When populations are high enough, L. dispar also feeds on conifers including eastern white pine, hemlock, and spruce.)
At this time in July, most Lymantria dispar caterpillars have pupated, and adult male moths may be seen flying in search of females. Adults will mate, and the female moths will lay brown/tan egg masses on nearly any flat surface, as seen here in Berkshire County, MA on 7/7/2021.
More good (mostly) news: most deciduous trees (as long as they are otherwise healthy and not stressed by other factors) can usually survive a single year of defoliation and may even send out a second set of leaves before the fall. Conifers on the other hand, unfortunately, are not usually so tolerant (even of a single year of defoliation). Multiple, consecutive years of defoliation can cause branch dieback and mortality of entire trees in some cases. Watering trees (when able and if necessary) and other actions to reduce additional stress at this time may be helpful for landscape specimens.
For next year: This coming fall and winter (after L. dispar females have completed their egg laying for 2021), scout your property and surrounding areas for overwintering egg masses. If there are a lot of egg masses visible, make plans with your local professional arborist and licensed or certified pesticide applicator to treat valuable specimen trees (especially those that were defoliated in 2021) when Lymantria dispar caterpillar eggs hatch and young caterpillars begin feeding in 2022. If caught early (when caterpillars are feeding and under approximately ¾ inch in length), a reduced risk option for managing Lymantria dispar is to apply Bacillus thuringiensis kurstaki to leaves of host plants that are being fed upon. But this must be done when caterpillars are still small and actively feeding. (Any lingering caterpillars present this season are too big to be effectively managed by Btk.) Another reduced risk active ingredient to consider next year, if needed, would be spinosad.
In the meantime, we can hope that the fungus (Entomophaga maimaiga) and the NPV virus will catch up with the population in Berkshire County and drop it below damaging levels, such as what was seen in the rest of Massachusetts in recent years. There may be some tree mortality, which is unfortunately not uncommon, but our forests have dealt with this insect since the 1860's - and they have been resilient. For more information about Lymantria dispar and how to identify caterpillars killed by the fungus and the virus, visit: https://ag.umass.edu/landscape/education-events/insectxaminer.
Q: I’m looking for help. I just noticed that I have MANY of these bugs in my vegetable garden. I lifted a pot that I had placed there last night and found even more. I don’t know if they are harmful to my veggies (will eat my produce) and if so, how I should safely deal with them?

A: What you have there are actually millipedes (Class: Diplopoda), so these are relatives of the insects but not insects themselves. Millipedes are characterized by having two pairs of legs per body segment, a characteristic that can be used to distinguish them from centipedes who possess one pair of legs per body segment. Millipedes feed on decaying organic matter and typically do not feed on or cause harm to living plants (including in vegetable gardens) unless the soil dries to the point where they may begin to feed on roots for moisture. Some damage to soft-stemmed plants has been reported in greenhouses.
Minimizing moisture and removing debris that trap in moisture (such as old pots, logs, rocks, boards, compost piles, and other items) near the garden may deter them from living in the area. Pesticides are not required to manage millipedes, and are often ineffective. Millipedes also provide a useful ecosystem service as macrodecomposers that accelerate nutrient cycling.
Q: I found this adelgid-like insect on eastern white pine (Pinus strobus). A bunch of the saplings at my property in NH are loaded. Should I worry?

A: The pine bark adelgid (Pineus strobi) will colonize the bark, needles, and candles of eastern white pine, Austrian pine, and Scotch pine. All life stages of this insect occur on pine hosts, unlike other species in the genus Pineus which alternate between pine and spruce. The pine bark adelgid overwinters in an immature stage on the bark of its host plant, and in the spring as temperatures warm they will begin to feed and secrete large amounts of white, waxy, woolly material over themselves, similar in appearance to the hemlock woolly adelgid. Mature females lay eggs which will hatch into crawlers, as well as winged individuals that disperse. Wingless forms may settle on the tree and reproduce repeatedly. Multiple generations occur per year.
Healthy, established, and mature trees are rarely impacted by the pine bark adelgid. Therefore, chemical management is rarely warranted. In high populations, entire trunks of trees may be coated in the white woolly material. If you find this unsightly, it may be sprayed off of the trunk with a strong stream of water from a hose. Beneficial insects also feed on pine bark adelgid, including but not limited to hoverfly larvae and lady beetle adults and larvae.

Tawny Simisky, Extension Entomologist, UMass Extension Landscape, Nursery, & Urban Forestry Program