STRIPPING TREES OF LEAVES AND FRUIT, CAUSING UNSIGHTLY INJURY
Aliases The Munch'
Inch Worm; Operophtera brumata
Hangout: Ornamental, orchard and forest trees,
especially oaks and maples
Physical Features: Young are green inchworms
(up to 1" long) with racecare white stripes on sides: adult males
are grayish brown with 1" wingspans, and appear hairy; females have
Winter moth larvae hatch and feed ravenously on leaves and fruit beginning
in early spring. Larvae feed on the inside of buds and leaf clusters during
the day, inching their way to the outside of leaves at night. In June,
larvae drop to the ground under the trees where they bury themselves in
the soil until fall. November through January, adults come out and mate.
Having no wings, females have a grueling climb up tree trunks where they
WET SUMMERS AND MILD, MOIST AUTUMNS ARE FAVORABLE TO WINTER MOTHS AND
MAY INCREASE THEIR POPULATIONS DRAMATICALLY.
Crunch the Munch!
1. Patrol the area
- In early spring, stake out
favorite daytime hangouts like inside buds and leaf clusters. At night
use a flashlight to look for dubious characters on the outsides of leaves.
- Search tree trunks for wingless
females in October through January.
- Look for devastated flower
buds and early dropping of petals from fruit trees such as cherry trees.
- Keep a record of what you
see and what you don't.
2. Make a positive I.D.
- These caterpillars should
be one of the only typical-looking inchworms around in early spring.
3. Do a thorough background
- Figure out which stages
of the winter moth lifecycle you can impact. If you're anxious to get
into the yard during the winter, search out females on warm, winter
evenings. These wingless females are easy to catch. Look for the cloud
of male moths around the tree trunk waiting for a chance to mate.
4. Determine the danger
- As with most pests that
cause leaf loss, established trees can bounce back from up to 25% leaf
loss for one or two years repeatedly.
Consider that winter moth is a cyclic criminal. It's here one year,
gone the next.
5. Make a plan
- Do-Nothing Method
-If the danger level is low enough, this is a good strategy. Remember
to consider the health of your tree and its ability to withstand some
leaf loss. -Trees that have been established for more than a couple
of years are quite able to defend themselves. Don't feel like you have
neglected your tree if you decide not to do anything. Winter moth is
subject to many natural predators and parasites.
- Manipulative Measures
-S.W.A.T. time! Search and destroy is the name of the game. Caterpillars
and wingless females are the easiest to annihilate.
-Your tree can defend itself if it's strong and healthy. Check with
Cooperative Extension if you aren't sure how to water or fertilize your
Roadblock female winter moths on their way to mate and lay eggs. Put
a 3-4" wide sticky barrier on tree gauze around the trunks of infested
trees. Both the sticky stuff and gauze can be bought at garden stores
for less than $10.
- Secret Agents
A gang of killers has increased its numbers in recent years and they
are hungry for winter moth larvae. They are parasitic flies that trick
winter moths into eating their eggs by placing them near recently munched
on leaves. As the egg hatches inside the winter moth, it literally eats
the moth inside out.
- Armed and Dangerous
-Suffocate winter moth eggs by applying dormant oil to your tree, purchased
from home and garden stores, during November through January. Follow
the label directions carefully to prevent scalding leaves.
-Bacillus thuringiensis (B.t) is deadly to caterpillars, yet it's less
toxic to other wildlife than most insecticides. It works best on young
caterpillars, so spray in early spring on a cloudy but warm day. (Sunlight
breaks down B.t.) -Look for products in home and garden stores that
contain B.t. and are registered for use on caterpillars.
-Don't forget to read and follow directions for use, storage, and disposal,
whenever a chemical is used.
6. Evaluate the results
- To improve your ability
to ward off this criminal, keep a record of which trees were victimized
by winter moth, what the percentage of leaf loss was, and if there were
any casualties. It's also a good idea to take note of the victims' health
prior to the attack, since healthy trees usually bounce back.