Squash Vine Borers

Squash plants can have huge, healthy leaves, ripening fruit, and, suddenly, everything wilts. If you live east of the Rockies, it may be squash vine borers. Unless the culprits are found and removed, your squash plant can be dead within a few days. (And if you happen to live west of the Rockies, reading this will prepare you for when squash vine borers expand their range!)

Squash vine borer (Jim, the Photographer) CC BY 2.0

Squash vine borers frequently attack Hubbard squash, pumpkins, gourds, and zucchini. Butternut squash, cucumbers, and melons are usually safe. 


Squash vine borer identification

Squash vine borers go through complete metamorphosis. The adult moths look like black and red wasps. They are approximately 1/2” long with transparent hindwing and metallic green front wings. Larva look like a fat, wrinkled, white caterpillar with a dark head. Eggs are tiny, flat, brown and oval.


Squash vine borer lifecycle

Adult borers overwinter underground in pupal cocoons. In early to midsummer, adult clearwing moths emerge and lay eggs near the stem of favorite foods. One or two weeks later, eggs hatch and the larval forms burrow into the crown and stems and begin feeding. Feeding will continue for 2 - 4 weeks. The fruit may also be eaten. One sign of squash vine borers is the appearance of piles of frass that look like wet sawdust.


​How to control squash vine borers

If a borer can be seen, it can be cut out of the stem, or a wire can be inserted into the burrow to kill the larva. If the stem must be cut into, use a very sharp knife and make a vertical cut


According to companion planting research, squash vine borers can be repelled by planting radishes nearby. Also, planting squash together with corn is said to disorient squash vine borers because of the different leaf shapes and stalk heights of the corn.


These tips can also help reduce the chances of squash vine borer infestations:

• Plant squash in a different location each year.
• While vines are small, sprinkle the area with diatomaceous earth (reapply after rain).
• Dispose of vines as soon as plants are done producing fruit.
• Use row covers.
• Place a yellow bowl filled with water where borers are suspected. (Adults are attracted to the color and drown.)​

If you live west of the Rockies and see a squash vine borer, please contact your local County Extension Office right away.