The Western Tussock Moth (Orgyia vetusta) found primarily in the Pacific Coastal
states and Idaho, can vary in numbers from year to year, with some years having high
populations, and other years where their impact is not even noticed.
The Tussock moth’s eggs begin to hatch in late February and the young larvae feed on
the remaining egg mass. These moths have an ingenious way of dispersing
themselves. They spin a silk thread used to “balloon” for dispersal. Because the female
is flightless, the young use this technique as the major form of moving around.
Typically, our attention is drawn to them from this behavior of dangling by a silk thread
from oaks and other deciduous trees. They also can be identified by the bright orange
and red spots among the tufted fuzzy hairs protruding from their bodies.
The larvae gorge on leaves until its time to spin their cocoons and morph into moths.
But when a tree becomes too crowded, they drop to the ground to crawl up another
tree. In this process they can at times cover homes, vehicles, patios and other
structures. The eerie image appears like something out of the “Twilight Zone”
Their behavior, as with all insects that have a complete metamorphous life cycle, where
there is a very active, ravenous larva, can result in anywhere from moderate to severe
damage to host and surrounding trees.
Healthy trees can usually withstand the damage and grow new leaves, but an all-out
attack can leave trees unattractively stripped of their canopy. If they suffer attacks over
several seasons death may result. In addition, the hair of the tussock moth caterpillar
can trigger allergic reactions. This may manifest itself by either a rash or if inhaled,
Killroy has many years of experience in dealing with this problem. While we can assist
you on an individual basis, it is more effective to treat the problem on a neighborhood
scale. If you begin to see signs of an infestation, check around your neighbors and see
if they are experiencing similar conditions. A comprehensive plan can be the most
effective method of controlling these pests. We can assist you with tips for a
coordinated neighborhood program.