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The Gypsy Moth

Gypsy Moth has been the topic of much discussion in recent years.  After signs of the pest in 2016 and a record breaking drought, Massachusetts was on track (in 2017) for the worst outbreak since 1981.  Egg masses on the trees forewarned a scene reminiscent of a horror film.  


What happened in 2017?

The cool spring weather and heavy rain tempered the initial eruption by delaying early feeding/defoliation. Waiting for the sun to shine, the caterpillars were in slow gear and essentially hibernated for a spell.  However, when the sun came out, these hungry pests "heard the dinner bell" and shifted into high gear.  Caterpillars went to work immediately, munching through entire trees in just a few days.  As a result, the beginning of the 2017 season proved to be very destructive.  Hiking through the forest, or driving through Metrowest Boston, one could get the impression that it is mid-winter.  Thankfully, those who treated their properties saw much less defoliation on their trees and are still enjoying shady backyards!

What does this mean?

Is there any good news in all of this?  Yes!  The very wet spring in 2017 encouraged the growth of a fungus that is a natural predator to the Gypsy Moth caterpillar.  Although we would have loved for this fungus to have taken affect before such widespread destruction occurred, it killed millions that had the potential to do much more damage....preventing those caterpillars from pupating, turning into moths, and laying eggs for future seasons.  This was encouraging as we looked forward to the 2018 season.  However, 2018 still showed signs of heavy infestation and the outlook for 2019 is guarded.  Egg masses are still prolific in many areas and those who were hardest hit in the past will likely be challenged by the pest again next year.  As always, we will keep a close eye on hatching patterns as we enter 2019.  We recommend that you renew your gypsy moth treatments to ensure a place on our spring schedule.

If you have questions about how your trees fared through this drama, our certified arborists would be happy to take a look.  Most trees can withstand one season of defoliation, but those affected year after year, along with lingering drought affects, may require a little extra TLC.  

Gypsy Moth caterpillars laying eggs on the base of a tree in 2016

Gypsy Moths will feed on almost any kind of tree. Here a pine at Rocky Narrows Reservation is nearly bare.

Egg masses on an oak tree....a common site in Metrowest Boston area and Route 495 regions.  White oak (pictured here) is among their favorite food.

A view overlooking the Charles River in Medfield....and a completely defoliated landscape (June 25, 2017)

The recent, wet weather has encouraged a deadly fungus that keeps the Gypsy Moth population in check.  Here, caterpillars are dying on the trees.

A caterpillar killed by the predatory fungus, due to a very wet spring in 2017.  If they are headed up the tree, death causes them to lose their grip and hang upside down.

If not for the shorts we were wearing, one would guess we were taking a winter hike.  Not a leaf remains on the forest trees. (2017)

A common site when fungus attacks the caterpillars.  Bodies start looking "dehydrated" and shrivel up.


A close up shot of gypsy moth egg masses (left) and females laying eggs at the base of a tree (right).

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