Squash Vine Borer
Squash vine borer larva |
The adult squash vine borer is a colorful
moth, 5/8 inch long with orange and black legs. The hind legs are
heavily fringed with orange and black hairs. The adult may be mistaken
for a wasp in appearance and flight. Young larvae hatch from dark
reddish brown eggs and grow to about one inch long with a whitish
body and brown head.
Habit
Adults emerge in late June and the first of July from overwintering
cocoons in the soil and lay eggs on all plant parts except upper
leaf surfaces. The majority of eggs are laid on the basal stem.
Hatching larvae usually bore directly into the stem and feed internally
for about 4-6 weeks, though some may feed externally prior to entering
the stem. At the end of this period, larvae enter the soil and spin
a cocoon about two inches below the surface. There is one generation
a year in northern and central Illinois and a possible second generation
in southern Illinois.
Squash vine borer damage |
Damage
The larvae bore into the stem and feed on tissue, hollowing
out the vines. The majority of larval activity will occur at the
basal four feet of vine. Plants wilt and usually rot and die beyond
the point of attack. The first indication of an attack will be the
sudden wilting of a long runner or of the entire plant. Upon close
inspection, frass may be found extruding from the infested stem.
Partial or complete crop loss may occur.
Control
Non-chemical: In the spring, cover the
plants with polyester row covers until blooming starts to protect
from egg laying moths. A second crop of zucchini or other summer
squash can be planted in early July to avoid borer attach. However,
an early Fall may result in litle or no crop. Certain squash varieties
offer an apparent resistance to and tolerance of borer attack. The
chart below indicates the susceptibility of 12 varieties, with a
rating of 5 indicating highly susceptible, while a rating
of 1 indicates fairly tolerant.
Variety of Type |
Rating |
Blue Hubbard (Hubbard type) |
5 |
Boston Marrow (Hubbard type) |
4 |
Golden Delicious (Hubbard type) |
4 |
Connecticut Field pumpkin (ornamental
type) |
4 |
Small Sugar pumpkin (ornamental
type) |
4 |
Zucchini |
4 |
White Bush Scallop |
3 |
Acorn |
3 |
Summer Crookneck |
2 |
Dickenson pumpkin |
2 |
Green Striped Cushaw |
1 |
Butternut |
1 |
Chemical: As soon as the vines begin
to run, a weekly preventive treatment should be applied to the basal
three feet of the plant. Contact your county
Extension office for current pesticide controls.
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