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GYPSY MOTHS GET SICK TOO!

In June, those large, black, hairy caterpillars

really begin to get your attention as they devour

your trees, pelt your car with unpleasant droppings, and lounge about on your porch. I am

describing the gypsy moth, of course, an annoying

caterpillar because of its voracious appetite, large

size, and abundance in many parts of eastern

North America.

You might be surprised by the sudden appearance

of dead gypsy moth caterpillars hanging on your

trees. Read on if you are curious about WHY they

died and HOW you can help control gypsy moths ,, ,

in your yard. Alarge, fungus-killed

/ gypsymothcaterpillar

Why are there so many dead gypsy moth [. usuallydieswithits

caterpillars in my yard? headstraightdown.

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Most of these caterpillars got sick and died ,,_"", t_t

after becoming infected with the gypsy moth ,!i'_l_]_i_t_/_

fungus, the gypsy moth virus, or both. _"/,;_]/]_! These "natural enemies" of the gypsy moth j i

help control them without spraying.

Is it normal for gypsy moth caterpillars to

Can a sick gypsy moth caterpillar recover rest on tree t_inks and houses? .

to become a moth? Yes. Large and healthy gypsy moth caterAfter a caterpillar gets sick, it will die before pillars often rest in the shade during hot,

becoming a moth. sunny afternoons. You will notice them on

tree trunks, with their heads aimed upCan the gypsy moth virus or fungus make ward, ready to crawl back up the trees to

me sick? eat again when it gets cooler. They become

No, neither will harm you, your pets, or very active when disturbed.

plants. The virus infects only gypsy moth

caterpillars. The fungus infects gypsy moth How can I tell if the gypsy moth caterpllcaterpillars and sometimes the caterpillars of lars in my yard are infected with the gypsy

closely related moths, moth fungus?

You will not know they are sick until they

Where did the gypsy moth virus and fungus are already dead. By mid-June, you may

come from? start to notice large, motionless gypsy moth

These natural enemies came from Europe caterpillars on tree trunks, firmly attached

and Asia, the original home of the gypsy to the bark by their feet, and hanging with

moth. When the gypsy moth first arrived in their heads down. They do not move when

North America over 100 years ago, its cater- touched. Such caterpillars probably died

pillars were healthy and they gradually from the gypsy moth fungus. Some may

spread throughout our eastern forests, look beige and dusty as they release tiny

Although some natural enemies of the gypsy fungal spores into the air. Over the next

moth were introduced to help control these few days and weeks, the dead caterpillars

destructive caterpillars, the gypsy moth virus become dry and stiff, fall to the ground

and fungus appeared unexpectedly. Gypsy around your trees, decompose, and release

moth caterpillars infected with the virus more fungal spores into the soil. These

were first noticed in 1907, and those infected spores will infect gypsy moth caterpillars in

with the fungus were first found in 1989. years to come.
How can I tel/if the gypsy moth caterpil- If there are lots of dead caterpillars on my

lars in my yard are infected with the gypsy trees this year, will I still notice gypsy

moth virus? moths next year?

Large caterpillars killed by the virus are Maybe, because neither the fungus nor

found about the same time as those killed virus kills every gypsy moth caterpillar. The

by the fungus. Virus-killed caterpillars, extent of gypsy moth control depends on the

however, hang in an inverted-V shape, number of fungal spores in your soil, patattached by some of their middle feet. terns of rainfall, and number of gypsy moth

Virus-killed caterpillars remain moist and caterpillars in your yard. However, this

limp and readily burst open, releasing a fungus can make gypsy moths so scarce

brown liquid containing gypsy moth virus, that you may not notice them for several

Although this is rather unpleasant, the virus years.

is harmless to everything except gypsy moth

caterpillars. Is the fungus or virus the same as the Bt

that is sprayed in the spring to control

How long does it take for the caterpillars to gypsy moth?

die from these diseases? No. Bt, short for Bac///us thur/ng/ens/s, is an

It takes about a week for the caterpillars to insecticide made from common bacteria

die from the fungus, and 2 to 3 weeks for found on leaves and in soil. When Bt is

caterpillars to die from the virus, sprayed, it is eaten by caterpillars, which

become sick and often die. Bt kills only very

How do caterpillars get sick? young gypsy moth caterpillars, so it must be

A caterpillar becomes infected with the sprayed early in the spring, soon after egg

fungus after a spore sticks to its skin and hatch.

begins to grow. A caterpillar must eat the

virus to get sick. Will my trees die if gypsy moth caterpillRrs

eat all their leaves?

Should I remove the dead gypsy moth Gypsy moth caterpillars prefer eating leaves

caterpillars on and around my trees? of deciduous trees---those that lose their

It is best to leave the dead caterpillars on leaves in the fall--like oaks and maples.

your trees because they contain fungus and Most deciduous trees can survive loss of

virus that can make other gypsy moth their leaves in the spring because they can

caterpillars sick this year and in the future, grow new ones. Watering your trees will

But it will not harm you to remove dead help them replace their leaves and stay

caterpillars if they are hanging on your healthier in case gypsy moths are abundant

house or are otherwise unsightly, for several years. This is especially important for newly planted trees or trees growing

Does watering around my trees help the in sandy or shallow soils.

fungus control the gypsy moth?

If rain is scarce during May and June, you Although the gypsy moth's favorite food is

can encourage gypsy moth fungal infections oak leaves, they eat leaves from almost any

by watering around your trees. Watering type of tree or shrub when hungry. Everalso helps your trees replace the leaves green trees, such as pine and spruce, are

eaten by caterpillars, likely to die after most of their needles are

eaten. But some trees recover and you can

Should I remove leaves and vegetation help by watering them well. However, they

from around the base of my trees? will look weak for several years before all

Where possible, avoid extensive landscaping their needles are replaced.

but retain leaf litter or encourage vegetation

around your trees because large gypsy moth

caterpillars often rest in shady places on the

ground to cool off. Gypsy moth caterpillars

that died from fungus eventually fall down Leah S. Bauer

to the base of trees and decompose, adding USDA Forest Service

more spores to the soil around your trees. Michigan State University

The exposure of healthy caterpillars to that East Lansing, MI 48823

soil encourages new fungal infections.