The Very Hungry Caterpillar.

I have a distinct memory last summer of enjoying a meal with a friend in her newly constructed screen house. I kept thinking it was raining due to the incessant pitter patter on the metal roof. When I later realized that it was gypsy moth poop, I had two thoughts. First, gross! And second, thank goodness for a roof!  Gypsy moths seemed to be everywhere.

If you thought last year’s invasion of gypsy moths was of biblical proportions hold on to your hat. According to experts, this year could be just as bad, if not worse.

In 2016 gypsy moths decimated acres of trees all over Massachusetts with damage especially apparent on the South Shore and Cape Cod. Last year’s infestation was the worst we’ve seen since 1981.

But what made it so bad?

Blame it on the drought.  According to experts, the gypsy moth population has been in check since 1989 thanks to a fungal pathogen. This fungus, which lives in moist soils attacks gypsy moths at the larval stage, thus holding down their numbers. Last year’s extreme drought made life less hospitable for the soil-borne fungus allowing larva to advance unchecked.

The constant munching by these little pests means that trees are left without leaves. Of course, when you consider that the purpose of a leaf is to provide food you understand how a tree can suffer without them.  Think of how you would feel after a 30-day fast. Now consider that we are in a drought. So there is very little water available as well. In this situation, whether we are talking about a tree or a person, you would end up with a very weakened specimen. In response to defoliation many deciduous trees will push out a second set of leaves but pines and other conifers are not able to do so and can suffer permanent damage. According to Joe Elkinton, a professor of environmental conservation at UMass Amherst and an expert on gypsy moths, ash trees are one of a few species that are never defoliated by gypsy moths.

Eggs left behind by last year’s moths mean the worst is not over. What can you do to protect your trees? First, know the preferred host trees of the moths, including, oak, maple, birch, poplar, willow, apple and hawthorne. 

 

If you have any of those trees, begin scouting for egg cases, which are typically tear drop shaped and 1-2 inches long. They are a buff-yellow color, are firm to the touch and look like they are made of felt.

 

They may be found in bark, along branches but also on patio furniture and car doors!

 

If you spot eggs the best bet is to contact a certified arborist who is a professional and will treat at the appropriate time.

Effective treatment will take place according to the developmental calendar of the pest, which can be estimated using Growing Degree Days (GDDs).  Knowing that gypsy moth eggs will hatch between 90-100 GDDs will ensure that any treatment is targeted. Treating willy nilly is not only dangerous, it is not effective.

Some people may decide to let nature take its course. But for others, who have valuable trees on their property,  a treatment plan is a good way to protect their investment.

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