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Squash Vine Borer FAQ |
Question:
My squash are dying. The stem just above the root turned yellow and rotted.
Minnesota Master Gardeners say:
Your squash probably have squash vine borer.
The key symptom is the appearance of soft, sawdust-like material (called
"frass") around the base of the stem. If you cut into the stem, you
may be able to find one of the borers, a white larva about an inch
long.
Squash vine borer will attack many squash plants, including summer
and winter squash, pumpkins and melons, although zucchini
seems to be a favorite. The moth form of the insect lays its eggs
in June. The larva then bores into the stem of the squash plant,
eventually killing the plant.
Squash vine borer is a very common problem and is difficult to control.
The best controls are preventative: use row covers to prevent the moth
from laying eggs in the early summer, plant resistant varieties,
make later plantings, and pull the dead plants promptly.
Dusting with carbaryl (Sevin) will also help control the moth. If
you use a pesticide, please follow the label precisely.
After the borer is present, there's not much you can do. We've had some
success slitting the stem lengthwise, digging out the borer, then
covering the stem with soil and watering. This is not a fun chore in
the middle of July! Zucchini seems to tolerate this surgery
better than the winter varieties.
It also helps to keep plant nodes (where the leaves emerge from the
stem) covered with soil as the vines lengthen, through the season. This
encourages rooting at each node and may keep the vine from wilting if
borers are present near the original root system.
For further reading:
Squash vine borer management in home gardens
http://www.extension.umn.edu/projects/yardandgarden/ygbriefs/e219squashvineborer.html