Frequently Asked Questions: Gypsy Moth Suppression Program
Oakland County, MichiganMSU ExtensionFrequently Asked Questions: Gypsy Moth Suppression Program

Frequently Asked Questions: Gypsy Moth Suppression Program

Please contact MSU Extension-Oakland to answer any of your questions or call 248-858-0900.

Do gypsy moth caterpillars make those ugly tents in the trees?

No, they do not make tents.  If you see them in spring, that is the Eastern Tent Caterpillar.

What do I do if I have gypsy moths?

First, contact your municipality.  They will usually take your name and address.  They will use this information to conduct their fall survey work to determine the severity of the gypsy moth infestation in the area.

Will I automatically be included in a treatment program if I have gypsy moths?

No.  Small numbers of gypsy moths are not a problem for the trees.  Municipalities do field work in the fall to determine what the insect threshold is.  If it qualifies for treatment, it is up to the municipality as to whether or not they want to participate in the treatment program.  The amount of acreage that qualifies in any given year will determine if treatment takes place.  Treatment can be expensive and may not be economically possible.

What pesticide is used to treat for gypsy moth?

Bacillus thuringiensis var. kurstaki or Bt for short.  This is a naturally occurring bacteria in soil that affects caterpillars.  The effectiveness of Bt is about 4 days.  The caterpillars must eat it to have it affect them so the timing of the Bt application is critical.

How is treatment applied?

From aircraft.  In Oakland County, a helicopter is used.  They fly just above the tree tops and spray B.T. into the trees.

Will gypsy moths kill my trees?

That depends.  Healthy trees can withstand about 50% defoliation without undergoing stress.  After that point the tree will push out a new set of leaves which is stressful as they should be using the energy to store carbohydrates for the next winter.  The new leaves will not get as large as the original set and there will not be as many of them, so the tree will not be able to manufacture the food it needs for winter.  This is the problem with the early season defoliators like gypsy moth.  Also, many of our trees are very old and the urban/suburban environment as well as weather can affect the health of our trees.