Many people ask me how to reduce gypsy moth damage on the trees in their yard. This page is a summary of what I do around our house.
NOTE: It is illegal to use pesticides on anything except for which it is registered. Also, registrations change periodically so be sure to check and follow the “label” of all pesticides before using.
LIFE CYCLE OF THE GYPSY MOTH
To control the gypsy moth around your house it is essential to know the life cycle.
Eggs: Gypsy moths pass the winter as an egg in buff coloured soft mass, usually on the trunk or the underside of large branches of trees. (Egg masses are also found on the sides of buildings, firewood, etc.) There are usually about 500 eggs in an egg mass.
Larvae: During May tiny caterpillars emerge from the egg masses. They feed until July. They prefer oak, walnut, willow, crab apple and Colorado blue spruce, but will feed on almost any type of tree or shrub.
Pupae: In July the caterpillars turn into moths by first entering a pupae stage. The pupae are smooth, dark reddish brown in colour and about 12 mm long. The moths emerge after about two weeks.
Moth: The male moth is brownish tan with well developed wings. The male is a strong daytime flyer. Compared to the male, the female is whiter, much larger and her wings are not well developed. (She cannot fly) Shortly after pupating, the moths mate, lay eggs and die.
CONTROL
The overall control method I use consists of the following:
Prevent the female moths and caterpillars from climbing the trees so that damage is reduced, and so that egg are more likely to be laid within reach where they can easily be destroyed.
Destroy all eggs and as many larvae and pupae as convenient.
METHOD:
In the spring place a strip of duct tape around the trunk of the trees you want to protect. This must be attached to the tree close enough that the small caterpillars can not crawl under it. If the bark of the tree is rough, I use a staple gun while I am applying the tape to make a tight fit in the bark hollows. Alternately, fill the spaces with spray foam insulation.
Coat the duct tape with a layer of “Tanglefoot”, (available at some garden centres). This stops the caterpillars and female moths from climbing the tree. Caterpillars and female moths that are already in the tree will often fall or jump out. The barrier prevents them from climbing back into the tree. Maintain this sticky barrier until egg laying is finished.
Destroy eggs in the nests by soaking them with dormant oil, (available at most farm and garden supplies). Do this in the fall when egg laying has finished. I experimented with WD40 and it was 100% effective. DO NOT GET EITHER MATERIAL ON THE NEEDLES OF COLORADO SPRUCE TREES! You could also remove the egg masses with a vacuum.
Kill as many of the caterpillars and pupae by crushing or cutting them while they are within reach, trapped below the tape.
SUMMARY
Keep the caterpillars out of the tree by preventing the eggs from being laid in the tree out of reach and by keeping caterpillars from climbing into the tree.
Destroy as many of the egg masses as possible. (The tape will keep the masses within reach)
Kill as many of the caterpillars and pupae as you can.
Good Luck!