Column, Tree Talk

Messy circumstances

By Gary Salmon

It’s been 30 years or so since gypsy moths were last here in any numbers and what a mess they made. The population was so large that they not only ate the leaves off their preferred oak trees but also other hardwoods like maples and then even to pines. It was easy to spot the caterpillars: they are hairy bodied with yellow bands and rows of red and blue spots. 

It is the sheer numbers of them that cause the “mess.” They poop constantly as they feed throughout the summer, congregate in masses all over trees, house siding, and in driveways, and the hairs are constantly falling off which can lead to allergy problems in humans. 

This latest outbreak is causing misery to the oaks and landowners in the Champlain Valley this summer but can easily expand into other parts of Vermont where oaks are growing come the next few years.

When populations explode one looks to see what has changed that allowed such an increase and in this case is appears to be a decline in the caterpillar-killing fungus — Entomophaga mainmainga. This population tends to decline during drought periods and the last few years have decreased this population. 

Homeowners, however, have resorted to novel control methods to keep their sanity, their oaks and yards less overrun, and from developing allergies from falling caterpillar hair. Burlap can be wrapped around oak trees, which attract the caterpillars and allow for removal. 

Duct tape smeared with petroleum jelly can be used much in the same way.  

A soapy water mixed with vinegar can be used on house foundations to deter them from congregating and in a worse case scenario that I remember from the last outbreak, getting out the snow shovel to collect those covering your driveway works.

But I digress over the mess. 

This all will end in late summer when the feeding stops and the female moth lays 600-1,000 eggs in a mass on oak trunks. They are covered in a light brown fuzz which insulates them from winter cold and prepares them to repeat the processes next spring. It is these egg masses that when surveyed will help determine steps that may be needed for “control” next year to protect our forest oaks. 

BTK, a bacteria-based organic pesticide, has been used for years to help keep forest populations of caterpillars under control and may be needed if these dry conditions continue. Or if we run out of burlap or snow shovels.

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