Gypsy Moth

Gypsy Moth Control Video

• Locating and destroying egg masses
• Using and servicing burlap hiding flaps
• Applying pesticide treatments
• Promoting the health and vigor of trees

 
Gypsy moth egg hatch begins in early to mid-May.  Citizens should locate and destroy as many egg masses as possible in April.  Each egg mass may contain between 50 to 1,500 eggs.  Gypsy moth egg masses are fuzzy, tan-ish brown, and irregular in shape, being wider at one end than the other.  Generally, they are laid against hard objects like tree trunks and limbs, not on the leaves or fine twigs.  They are often found on the underside of tree limbs, under the eaves of houses, and under deck railings and play structures.  Birdhouses are magnets for female gypsy moths looking to lay eggs.

A few days after the eggs hatch, the gypsy moth caterpillars can be controlled with applications of the biological insecticide Bacillus thuringiensis (B.t.), a naturally occurring bacterium.  It must be applied to the foliage of the plants the caterpillars are feeding upon and will only control them while they are still very small, becoming less effective as they grow larger (early June).  Homeowners can treat small trees relatively easily using handheld sprayers.  For larger trees, residents may need to hire a tree or landscape service to do the spraying.  Be sure to get multiple quotes from reputable companies (check their references and insurance coverage) and look for companies having "certified arborists" on staff.  

As the caterpillars grow larger and more noticeable, they begin to make daily migrations down the tree during the day to hide and rest.  Beginning in June, you can place and service burlap hiding flaps.  Hiding flaps can be made from 18'' X 24'' sections of burlap.  Fold the top half down over the bottom half, creating a double flap 18'' X 12''.  Place the burlap at a convenient working height on the trunk of the host tree and staple to the tree's bark at the fold.  Lift the flaps one at a time and hold up by using a thumbtack or pushpin.  Use a small brush to sweep the caterpillars into a container of soapy water, which kills them quickly (insecticidal soap works best).  The caterpillars should be removed and destroyed daily.  The best time to service the burlap is mid-day, but late afternoon or early evening may also be effective. 

Leaving the burlap in place during caterpillar pupation and the adult egg-laying period (July – August) will often encourage the female to deposit the egg mass behind the flaps.  Providing that type of hiding place enables the homeowner to more easily locate and destroy the egg masses.  You can remove the burlap by September.  Do not destroy the egg masses until April to allow egg parasites to complete their life cycles and to allow Forestry staff and volunteers to conduct the annual egg mass survey.

Finally, keeping trees healthy by proper watering, mulching, and fertilizing will maximize their ability to sustain attack from the gypsy moth.  Cultural practices alone will not prevent caterpillars from feeding, but healthy trees have greater energy reserves and can therefore rebound more readily after being damaged.  Maintaining a diversified landscape that includes tree and shrub species that are rarely attacked by the gypsy moth also tends to reduce damage to susceptible species.  Tree species that are not normally damaged by gypsy moth include maples, horse chestnuts (buckeyes), hackberry, locusts, coffeetree, tuliptree, blackgum, planetree (sycamore), baldcypress, and elms.

Forestry staff is available to demonstrate the proper placement and servicing of burlap hiding flaps.  Click here to view a video of the burlapping technique. The Forestry Division also has written information available to citizens detailing how to identify the gypsy moth at all stages of its life cycle, and effective control strategies that can be implemented throughout the year.