Understanding & Managing Forest Tent Caterpillar
Forest Tent Caterpillar
Deciduous Trees
What is Forest Tent Caterpillar?
Photo, top right: Shiny black egg masses can be seen encircling twigs. (James B. Hanson, USDA Forest Service, Bugwood.org)
Above: Caterpillars are gregarious, hanging out in large groups on
trunks and major limbs. (Steven Katovich, USDA Forest Service, Bugwood.org) Below: Caterpillars build cocoons on the sides of buildings or any other protected structure. (James B. Hanson, USDA Forest
Service, Bugwood.org)
Native to North America, the forest tent caterpillar, Malacosoma disstria,
strips the foliage from trees, builds cocoons on the sides of buildings, and
becomes messy when crawling on sidewalks, patios, and driveways where
they are frequently squashed. Forest tent caterpillars are active from midspring through early summer and are easily visible as they congregate on
branches or tree trunks. Multiple years of defoliation can tax a tree’s energy storage, leaving it susceptible to further insect or disease problems.
Biology
Forest tent caterpillars have one generation per year. Larvae emerge in midspring and the caterpillars feed for about 5-6 weeks. In late spring and early
summer, mature caterpillars move from their feeding sites in search of a protected area to pupate in their silky cocoons. Approximately two weeks later,
adult moths emerge and lay shiny, black egg masses around small twigs.
Susceptible Trees
A number of deciduous trees act as hosts including aspen, oak, birch, ash,
maple, elm, basswood, water tupelo, sweetgum, red alder, willow, and cherry.
Signs and Symptoms
• Stripping of foliage from mid-spring to early summer.
• Shiny black egg masses are often visible encircling twigs.
• Young larvae are black, hairy, and about 1/8 inch long, often visible in
groups on twigs and trunks.
Forest Tent Caterpillar Treatment Strategies
From left to right: Lepitect™ is a soil injected insecticide. One packet treats 50 diameter inches for tent caterpillar. Up-Star® Gold is a
spray applied insecticide for tent caterpillar. A hand pump sprayer like
this one is used to apply spray products like Up-Star® Gold.
Treatment Strategy
New soil applied insecticide technology has made forest tent
caterpillar easy to control. Lepitect™ soil applications provide a
greater window of control than sprayed insecticides, and should
be applied as leaves are fully emerged in the spring. A second
treatment may be used thirty days later if larvae are still active.
Sprayed treatments of Up-Star® Gold can provide excellent control; however, if treating a large tree, foliar applied treatments may
be too environmentally risky. Drift and contact with non-target
insects are common concerns, making soil applied treatments the
preferred method for many professional
arborists. When choosing insecticides be
sure to choose one that controls lepidopteron insects, most insecticides do not
control this insect type.
DIY Shopping List
Option 1:
Option 2:
Application Type –
Soil injection
DIY Product/Equipment Needed
Application Type –
Foliar spray
DIY Product/Equipment Needed
o
o
o
Lepitect™
Measuring or diameter tape
HTI Soil Injection Kit
Timing
Late spring as leaves are at full
emergence. A second treatment
may be applied 30 days later.
o
o
Timing
As insects are visible. Follow up
treatments may be applied 14 days
later throughout the season to control feeding caterpillars.
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Up-Star® Gold
Hand pump sprayer with wand