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University
of Rhode Island GreenShare Factsheets
Squash
Bug
Anasa tristis
Hemiptera: Coreidae
The squash bug is one of the most common and troublesome
pests attacking squash and pumpkin plants. Both nymphs and
adults suck sap from the leaves and stems, apparently also
injecting a toxic substance into the plant, causing a wilting
known as Anasa wilt of cucurbits. This closely resembles bacterial
wilt, a true disease. After wilting, vines and leaves turn
black and crisp and become brittle. Small plants are killed
entirely, while larger plants may have several runners affected.
Squash bugs are often found in large populations, congregated
in dense clusters on vines and unripe fruits. Sometimes no
fruits are formed as a result.
Adult squash bugs are rather large, about 12 mm (1/2
inch) long and approximately 1/3 as wide. Adults are winged,
brownish black, sometimes mottled with gray or light brown
and flat-backed; they give off a disagreeable odor when crushed.
The nymphs are whitish to greenish-gray with black legs. Squash
bugs vary in size from tiny, spider-like individuals when first
hatched to the maturing nymphs which are nearly as large as
adults. Young nymphs have red legs and antennae with a green
abdomen. After aging a few hours, the red parts become black.
Late instar nymphs are a dark, greenish-gray color. Eggs are
yellowish-brown to brick red and are laid in groups or clusters.
Unmated adult squash bugs overwinter in the shelter of
dead leaves, vines, boards or buildings and fly to cucurbits
when vines start to grow. Following feeding and mating, egg
laying soon begins. Masses of eggs, each containing about a
dozen or more, are usually deposited on the undersides of leaves
in angles formed by the veins. Egg laying by the overwintering
females continues until midsummer. Eggs hatch in about 10 days
or more, and the nymphs pass through 5 instars requiring 4-6
weeks to reach adulthood. Only one generation develops each
year and new adults do not mate until the following spring.
Squash bugs are secretive in habit. Both adults and nymphs
are found clustered near the plant crown, beneath damaged leaves,
under clods or in any protective groundcover. They all scamper
quickly for cover when disturbed. Because of the protracted
egglaying period, all life stages occur throughout the summer
months.
Early detection of adult squash bugs is very important,
as they are difficult to kill and can cause considerable damage.
Prevention: If only a few vines are involved, it
is best to collect and destroy the bugs and crush their egg
masses. Some people place pieces of board or shingles on the
ground near the plants to concentrate the number of individuals
in an accessible area. Plant remnants may be composted or burned
at the end of the year. It is a good idea to select varieties
of squash and pumpkin resistant to the squash bug. Since there
is only one generation per year, damage can be greatly reduced
by keeping vines covered until blossoming begins. Remove the
cover for pollination purposes.
Insecticides: If mechanical and cultural controls
are inadequate, chemical insecticides registered for garden
use can be applied, according to label directions and safety
precautions. Repeat applications may be needed.
Adapted from the
Ohio State University Extension, 1999
Pesticides
are poisonous! Read and follow all safety precautions on labels.
Handle carefully and store in original containers out of reach
of children, pets or livestock. Dispose of empty containers
immediately, in a safe manner and place. Pesticides should never
be stored with foods or in areas where people eat.
When trade names are used for identification, no product endorsement
is implied, nor is discrimination intended against similar materials.
Be sure that the pesticide you intend to use is registered for
the state of use.
The user of this information assumes all risk for personal injury
or property damage.
For more
information, call the URI CE Gardening and Food Safety Hotline
at 1-800-448-1011 or (401)874-2929 from outside Rhode Island;
Monday-Thursday between 9 am and 2 pm.
University
of Rhode Island Cooperative Extension provides equal program
opportunities.
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