I was thinking that gypsy moths were no longer a problem near
Pittsburgh, but they just killed two pine trees in my yard. I didn’t
realize that was happening until a few days ago. The gypsy moth
caterpillars are crawling all over my house like summers in the late
1980’s. Are gypsy moths back? What can I do to control these large
While gypsy moths (Lymantria dispar) have been pretty much under control
in our area for the last 15 years or so, they will never be
completely eradicated. They were introduced into Massachusetts in
1869 by Leopold Trouvelot for his silkworm-breeding program. A
number of the insects escaped, and by the early 1900’s were
responsible for major defoliation of forests in New England. Gypsy
moths arrived in western Pennsylvania in the late 1980’s and have
continued their westward movement as far as Minnesota.
Origins of the
name Gypsy Moth
name “gypsy moth” comes from the way they move from area to area: on
the wind. Their progress across the country has been slowed by our
prevailing winds from the west; had they been introduced on the west
coast, they would have covered the United States long ago.
White Oak is one of the favorite foods
of Gypsy Moth caterpillars
When an introduced pest like the gypsy moth enters a new area, it
takes a while for natural predators such as parasitic and predatory
insects to kick-in. A combination of well-timed insecticidal sprays,
introduced pathogens, predators and parasites worked to bring gypsy
moths under control here after their initial plague-like arrival.
Their populations build up to outbreak proportions every five to ten
years, depending on weather conditions. A big factor in reducing the
gypsy moth population to a tolerable level has been a fungus that
infects and kills the pest, Entomophaga maimaiga. Years of
plentiful rain help the fungus spread, while dry years cause the
fungus to die out.
If you have never had the dubious pleasure of seeing gypsy moths,
young caterpillars are gray-brown and very hairy. Their hatch
coincides with the leafing out of their favorite food, white oaks.
Adult caterpillars are also hairy, and are characterized by five
double rows of blue spots followed by six double rows of red spots
on their backs.
Photo ©2008 donnan.com
Gypsy moth caterpillar?
double rows of blue spots
followed by 6 double rows of
red spots on its back.
caterpillars stay in the tree and feed day and night, older
caterpillars feed only at night. They rest under leaf litter on the
ground and in bark crevices near the base of host trees to avoid
desiccating or being eaten by predators. Only mature gypsy moth
caterpillars feed on conifers, like your two pine trees.
Gypsy Moth Caterpillars
Mature caterpillars are beginning to pupate, so the window for
controlling them is closing fast. You may get control with Sevin
(carbaryl) or Bayer Advanced Power Force Multi-Insect Killer
(cyfluthrin). If your pines are very large, you should contract
a tree service with a certified arborist on staff to spray them.
They have the proper equipment and training to do the job safely and
State foresters monitor gypsy moth populations on state and federal
forestlands, and use their findings to target regions for aerial
spraying. A total of 221,831 acres in 27 counties in northeastern
and central Pennsylvania was treated in 2008. The aerial sprays
used by the State are biological controls, either Bt
(Bacillus thuringiensis) or Gypchek (gypsy moth
nucleopolyhedrosis virus). They are both very safe for people,
pets, birds, wildlife, and even most other insects. Both are most
effective on young caterpillars.
Private landowners in forested areas must contact their county gypsy
moth program coordinators by July 15, 2008 to have their property
evaluated to see if it qualifies for inclusion in the state’s 2009
gypsy moth suppression program. County gypsy moth program
coordinators' contact information can be found on the
Pennsylvania Department of Conservation and Natural Resources web
Residential property owners will have to contract with a commercial
arborist to have their trees sprayed for gypsy moths.
Emerald Ash Borers (EAB)
When Lilacs are not Blooming