MIMOSA WEBWORM
DESCRIPTION
Mimosa Webworm is an insect native to China and Japan and
was accidentally introduced into the U.S. earlier in this
century. The caterpillars were first detected in
Washington D.C. in 1940 attacking mimosa trees. Today the
moth is common in many states and is a major pest of
mimosa and honeylocust.
Despite its name, Mimosa Webworm is found more commonly on honeylocust than on mimosa in Pennsylvania. The moths are small, with a wing expanse of about one-half inch. The forewings are grayish with small black dots; the grayish hind wings lack the dots. The caterpillars are brownish with five longitudinal whitish stripes and slightly more than a half-inch long when mature.
LIFE CYCLE
Adults emerge in early June from pupae that overwinter in
the ground or in crevices on the host tree, and they
oviposit on flowers and foliage. Newly hatched
caterpillars feed together in the foliage they web, and
later they move to the tender terminal leaves and feed,
continuing to web the foliage. Larvae feed on the
undersides of the leaflets, leaving the upper surface
intact. The caterpillars complete feeding about mid-July
and pupate in the ground or in the webbed foliage. Adults
of the second generation emerge in about two weeks, and
the cycle is repeated, requiring about four weeks.
DAMAGE
Attacked leaflets turn brown and detract from the trees'
appearance causing an unsightly condition. Heavily
infested trees appear dull gray to brown and undoubtedly
are stressed to some extent. The stress factor may be
increased if the trees were heavily attacked by
honeylocust plant bug, the major early-season pest of
honeylocust in Pennsylvania. Activity on honeylocust
begins about the time the plant bug has completed it's
feeding and egg-laying on the tree.
CONTROL
Formulations of acephate (Orthene), bacillus
thuringiensis, carbaryl (Sevin) and cyfluthrin (Tempo II)
are labeled for Mimosa Webworm control.* Follow all label
directions for specific information on host plant label
clearance, phytotoxicity information, safety precautions
and dosage information.
* See Woody Ornamental Insect, Mite and Disease Management, The Pennsylvania State University (2005) for more details.
WARNING: Pesticides are poisonous. Read and follow directions and safety precautions on labels. Handle carefully and store in original labeled containers out of reach of children, pets and livestock. Dispose of empty containers right away , in a safe manner and place. Do not contaminate forage, streams or ponds.
For professional assistance
with tree and shrub problems,
contact Keystone Tree Experts at (215) 348-4444.
