Squash vine bore and squash bugs
Squash Vine Borer
The squash vine borer is a key pest of winter
squash, gourds and pumpkins in Kentucky.
Unfortunately, it is usually noticed only after it
has done its damage. Symptoms appear in
mid-summer when a long runner or an entire
plant wilts suddenly. Infested vines usually die
beyond the point of attack.
R. Bessin, Univ. of Kentucky Entomology
Sawdust-like frass
near the base of the
plant is the best
evidence of squash
vine borer activity.
Careful examination
will uncover
yellow-brown
excrement pushed
out through holes in
the side of the stem
at the point of
wilting.
If the stem is split open, one to several borers
are usually present. The caterpillars reach a
length of 1 inch and have a brown head and a
cream-colored body. Winter squash, particularly
'Hubbard', are most susceptible to damage
while 'Butternut' is somewhat resistant.
The adult squash vine
borer is a stout dark
gray moth with 'hairy'
red hind legs, opaque
front wings, and clear
hind wings with dark
veins. Unlike most
moths, they fly about
the plants during the
daytime, appearing
more like a paper
wasp than a moth.
R. Bessin, Univ. of Kentucky
This insect overwinters as a full grown larva or a
pupa one to two inches below the soil surface.
If it has not already done so, the larva pupates
in the spring. Adult moths begin to emerge
about the time the plants begin to run, and
moth flight continues through mid August.
The small brown eggs, laid individually on leaf
stalks and vines, hatch in seven to 10 days. The
newly hatched larva immediately bores into the
stem. A larva feeds for 14 to 30 days before
exiting the stem to pupate in the soil. There are
1 to 2 generations per year in Kentucky.
Management
The key to squash vine borer management is
controlling the borers before they enter the
stem. Once inside the vine, insecticidal control is
ineffective. Poor timing of sprays is the usual
cause of inadequate control. Monitor plants
weekly from mid-June through August for initial
signs of the borer's frass at entrance holes in
the stems. Very early signs of larval feeding
indicate that other eggs will be hatching soon.
Use two insecticide applications 7 days apart to
control newly hatching larvae and continue to
monitor for additional activity. Sprays need to
penetrate the canopy to cover the vines to be
effective.
Home gardeners may have some success with
deworming the vines. At the first signs of the
sawdust-like frass, vines are slit lengthwise near
where the damage is found and the borers
removed. The stems should be immediately
covered with earth. Sanitation is also important.
After harvest is complete, vines should be
removed from the garden and composted to
prevent the remaining borers from completing
larval development. Burying a few nodes along
each vine will encourage rooting at these
nodes. This will lessen the impact if squash vine
borers girdle the base of the vine.
Squash Bug
R. Bessin, Univ. of Kentucky Entomology
The squash bug is
another common
pest. While all of the
cucurbit crops can be
attacked, it shows a
preference for
squashes and
pumpkins. This insect
can be very difficult
to control when
populations are
allowed to build.
Squash bugs damage plants by removing sap
and causing leaves to wilt and collapse. Young
plants and infested leaves on older plants may
be killed.
Only the unmated adult bugs overwinter in
Kentucky. Adult squash bugs begin to fly into
fields and gardens about the time the plants
begin to run. They remove plant sap with their
piercing-sucking mouthparts.
R. Bessin, Univ. of Kentucky Entomology
Soon after beginning
to feed, they start
laying eggs, primarily
on the undersides in
the angle between
veins. The bronze
eggs are
football-shaped and
lie on their sides in
groups of 12 or
more.
Eggs hatch in one to two weeks. Initially the
larvae are dark red with a light green
abdomen.
Older nymphs are
light gray in color
with black legs.
Young nymphs are
gregarious and feed
together in groups.
Nymphs require five
to six weeks to
mature into adults.
R. Bessin, Univ. of Kentucky Entomology
Squash bugs spend most of their time around
the base and stems of the plants and on the
undersides of leaves.
Management
Timing is the key to successful squash bug
control. Insecticide sprays should target adults
and small nymphs early in the season when the
plants are small. It is much more difficult to
control large numbers of older nymphs and
adults later in the season when the plant
canopy is dense. Treat with a recommended
insecticide (See ID-36, Commercial Vegetable
Crops Recommendations) if overwintering
adults are causing seedlings to wilt.
Monitor for squash bug egg masses from
prebloom through early flowering. Treat when
egg mass numbers exceed an average of one
per plant. However, eggs are not controlled by
insecticides, so time insecticide applications to
control young nymphs. Small nymphs are much
easier to control with insecticides than larger
nymphs or adults.
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