- These oakworms occur
throughout the United States.
The first indication of their presence is often fecal
pellets on the driveway or sidewalk under an oak tree. They are
voracious feeders, and where abundant, quickly strip the trees
of their foliage. Since defoliation takes place in late summer
to fall, however, forest stands of white and red oak are
generally able to survive with only minimal growth loss or crown
dieback. The greatest damage is the aesthetic impact and
nuisance the caterpillars create in urban areas. As the
caterpillars mature, they are often seen crawling along
sidewalks and driveways, yards, etc. searching for a place to
pupate.
Identifying the Insect.
- The larvae of the
orangestriped oakworm are black with eight narrow yellow
stripes, the pinkstriped oakworm larvae are greenish brown with
four pink stripes, and the spiny oakworm larvae are tawny and
pinkish with short spines. Eggs are white, but become pinkish to
brownish gray before hatching. Larvae are about 2 inches (50
mm) long and have a pair of long, curved "horns". The adult
moths are a similar yellowish red, with a single white dot on
each of the forewings.
Full-grown orangestriped oakworm caterpillars.
Identifying
the Injury. -
Young larvae feed in groups, skeltonizing the leaf. Later they
consume all but the main veins and usually defoliate one branch
before moving onto another. Older larvae are less gregarious
and can be found crawling on lawns and the sides of houses.
Biology. -There are 5
instar stages that mature in May or early June.
These first
generation adalts females moths oviposit eggs clusters in June
and July. The deposited egg clusters are of several
hundred eggs on the underside of leaves that eggs hatch within a
week, and the larvae feed during July to September for 5 to 6
weeks. The pupae overwinter in the soil. The orangestriped and
spiny oakworms have only one generation per year, while the
pinkstriped oakworm has two generations.
Second-generation moths occur in October and November when they
oviposit eggs that hatch into overwintering larvae. There are 2
to 3 generations year.
Control.
- Natural enemies generally
prevent widespread defoliation. Chemical control may
be needed for high value trees.
The
best way to treat your plants for worms is with Bacillus
Thuringiensis or Bt. ( a biological control agent that
only targets and kills the pest ). Also known in garden
centers under the brand name Thuricide, Cry-Maxx or Despel. It
is an organic product, though use standard application
precautions just to be safe. It targets kills caterpillars
(worms) and not most beneficial insects.
