Pesky Caterpillars Destroying Rhode Island Trees

DEM released flies that feast on the winter moth in some communities in an effort to reduce their populations.

Cute, but destructive caterpillars are destroying trees in Rhode Island. (Photo: Rhode Island Department of Environmental Management)
Cute, but destructive caterpillars are destroying trees in Rhode Island. (Photo: Rhode Island Department of Environmental Management)

The Department of Environmental Management reports that winter moth caterpillars are prevalent throughout Rhode Island and are causing defoliation on oak, maple, ash, basswood, elm, beech and fruit trees. 

According to Bruce Payton, state forester and deputy chief of DEM's Division of Forest Environment, communities across the state reported the emergence of millions of winter moths, Operophtera brumata, from late November through December.  “It is no coincidence that, in the spring, these same communities are seeing an astonishing number of caterpillars defoliating deciduous trees,” he said. The tremendous growth of the caterpillar population has affected the entire state. Leaves on affected trees are filled with small holes and have a shotgun-hole appearance.  

Winter moth caterpillars are pale green with white longitudinal stripes running down both sides of the body. Also referred to as “loopers” or “inchworms,” they are often found in association with both fall and spring cankerworms, which look similar and have similar feeding patterns. Payton said that heavily defoliated trees will be stressed, and that the trees must put out a second flush of growth in order to survive. Water is critical to trees at this time. Supplemental watering of trees will be necessary if drought conditions occur. Fertilizer application is not recommended at this time for trees that have been defoliated. 

In an effort to control the winter moth population, researchers from DEM in conjunction with URI and Joseph Elkinton, PhD of the University of Massachusetts Amherst released a parasitoid fly that feeds exclusively on winter moth in early May in several Rhode Island communities. This is the third year that this parasite has been released in the state; the hope is that it will become established and eventually act as a control agent for the winter moth population. A natural enemy of the winter moth, Cyzenis albicans has been effective in mitigating large populations of winter moths in Nova Scotia. However it will take several years for populations of the parasite to catch up with the population and spread of winter moths. 

DEM’s Division of Forest Environment is tracking the areas where winter moth infestations are most prevalent in the state and is asking the public to report instances where trees are heavily defoliated.  The location, along with a contact name and phone number can be emailed to Bruce Payton at bruce.payton@dem.ri.gov or Paul Ricard at paul.ricard@dem.ri.gov.  

Linda Mulzer May 23, 2014 at 10:37 AM
Can anything be done to stop them such as tape that was put on trees during the gypsy moth infestation in the 80's?
peasunshine May 25, 2014 at 09:27 AM
As a butterfly gardener this concerns me. What else will these flies eat besides these specific caterpillars? Also, if you look around Rhode Island, you'll see quite the over abundance of trees casting way too much shade and blocking out the sun, and causing flowers in my garden to struggle. If that weren't bad enough, the pollen from oak and other trees are making a plethora of people quite ill. The leaves of the trees of oaks don't decompose well, and the acorns have already caused me two concussions as well as doing extensive damage to cars, homes, and many others. What would be wrong with letting nature alone on this and maybe birds that are feeding their young and other hungry animals could have it easy this time?
Dee Wood May 25, 2014 at 08:27 PM
You know, peasunshine, maybe you were hit on the head by those Oak tree acorns too many times. First of all, Oak trees can take up to 100 hundred years to grow...and those head bombing acorns you speak of were considered food for some in our bygone days...not to mention our animals and birds today. It stands for strength and endurance...it's even been named America's National Tree by the act of Congress. Why not try to grow a humble tree from an acorn that caused one of those concussions !!
Brooke Merriam May 26, 2014 at 06:46 AM
Peasunshine, if you are really a butterfly gardener you should embrace the oak trees, because they support more species of butterfly ( and many other types of wildlife) than any other plant. Also, the wasp they've released only eats the winter moth caterpillar. To be glad to see large native trees getting decimated by an invasive, non native pest is a little naive.


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