The White-Marked Tussock Moth Caterpillar

The White-Marked Tussock Moth Caterpillar
By George Giltner, Master Gardener

2013 WMTM

The caterpillar of the White Tussock Moth

Ouch! Most of us in forested areas have come in contact with these little tuffed (tussocks) hair caterpillars with short, bristly, toxic pincushion hairs on their backs.  These stinging hairs cause a very irritating rash especially on the inner arms, neck, and stomach areas.  Where do they come from?  Look no further than trees and brush as these caterpillars feed on a large variety of leaves including oak, pecan, hickory, walnut, willow, rose, maple, pear, and many others, including conifers.

The population densities cycle from year to year with very high numbers one year, then possibly no reports the next year.  They can cause economic loses of newly planted trees (1-3 years old) when complete defoliation occurs.  Healthy developed trees usually recover even when they are completely defoliated.

A positive ID is made by observing the orange head, tuffs on the back, and red dots on the hind abdominal segments that are in line with a dorsal black stripe.  Also look for the brown, paint bush tail hairs. The white-marked tussock moth is related to the gypsy moth, family Lymantriidae, which also has the tussock stinging hairs on the larvae.

To control the young caterpillars (less than ¾ inches) use Bt products like Dipel or Thuricide.  For the larger caterpillar that can reach 1.25 inches, use pyrethroids (synthetics), pyrethrums (natural), or spinosad products.  Birds are voracious feeders on the large caterpillars.

The caterpillars first appear in early April after overwintering in the egg stage.  Then they go through several enlargement stages during 35 days to pupation.  The gray cocoons with silk threads may be noticed in the bark of host plants.  The adults emerge in about 2 weeks, mate, and then die.  The males are born with well-developed wings, but the females are forced to stay local with undeveloped wings. Three generations per year are normal for the white-tussock moth, Orgyia leucostigma.


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