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Spongy (Gypsy) Moth Suppression

Much is being done in the U.S. and Canada to slow the spread of spongy (gypsy) moth into uninfested areas but for most of us in the Eastern and Midwestern states, prevention is no longer an option.  We are infested and will remain that way.  But much can be done to prevent the nuisance and tree damage caused by spongy (gypsy) moth.

Spongy (gypsy) moth suppression programs can be put together to handle a crisis situation or they can be ongoing, monitoring the population and spraying when necessary.  Most people prefer the second method.  This way they know the gypsy moth problem is being addressed each year and they can go about their activities with good assurance that the moth will not interfere   The ongoing suppression programs are also the most effective, with very high accuracy and success rates. 

The two main parts of any spongy (gypsy) moth suppression program are:  population monitoring and the actual aerial spray.

The monitoring is necessary to know where to spray so that time and resources are not wasted.  The spray drives down the population so that the natural controls can have a chance to function.  The monitoring is done in the fall and early winter.  The spray is done in the spring about two or three weeks after the majority of the spongy (gypsy) moth caterpillars have hatched.  This is usually late April to late May.

Population Monitoring

Aerial Spray

All spongy (gypsy) moth suppression programs are designed to prevent the defoliation and loss of the primary host trees.  It is very devastating to a home to lose large mature trees that have taken decades to grow.  Trees furnish shade, wind protection, increased water absorption  soil anchoring, nesting sites, and food for a host of desirable animals.  The aesthetic value of trees is also very high and adds much to a livable yard.  The first goal of suppression is to keep these valuable trees healthy and strong.

The second goal of the more aggressive suppression programs is to reduce or eliminate the nuisance of the spongy (gypsy) moth.  Large numbers of caterpillars cause all kinds of stress to those who have to live under them.  Even people accustomed to nature don't like the continual rain of caterpillars, shredded leaves, and frass.  Continuous population monitoring can detect when the populations are rising to the point of becoming nuisance, and the spray can stop most of this from ever happening.

There have been a number of economic studies comparing the cost of spongy (gypsy) moth suppression programs with the cost of removing or salvaging the dead trees.  There are many variables but most studies show a 7:1 or better benefit to cost ratio for the spongy (gypsy) moth spray intervention.  And most of these studies do not put a monetary value on the aesthetic value of the trees!

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