How to Deal with the Worst Squash Pest, The Vine Borer

By: Jackson Hambrick

In St. Louis, right around now is the time to start planting zucchini and summer squash. These plants love our long summers and produce lots of fruit but lots of gardeners have trouble with pests getting to them.


“Vine Borer Damage on Zucchini Plant” by thesoutherngardener is licensed under CC BY-NC-SA 2.0

One of the most common pests that kill squash is the Squash Vine Borer. If you have had problems in the past with your squash plants looking healthy one minute and then wilting and dying out of nowhere then you may have had vine borers. This is a tell-tale sign of them because the borer eats its way up into the base of the squash plant and prevents nutrients and water from being taken up by the roots and reaching the rest of the plant.

There are few options for dealing with vine borers. First, you may want to plant varieties that the vine borers do not find as tasty. If you like zucchini or summer squash, think about trying Tromboncino squash. If you are looking to replace pumpkins or winter squash you can try Seminole Pumpkins. Both of these varieties have little to no pest pressure from vine borers. But if you do not want to grow those varieties you still have some options. The Squash Vine borer starts as cocoons in the ground. In Missouri, the adult moth emerges from the cocoon around late May to June. The moth’s wings are green and it has an orange and black body. It looks similar to some wasps.


Once the moth has emerged it lays eggs at the base of squash plants. About a week after the eggs are laid they hatch the borers that eat their way up into the squash plant. After they’ve had their fill in the squash plant which is about a month to six weeks, they go back underground and stay underground until the next summer.


A bed of summer squash covered with insect netting

The simplest method to prevent squash borers is to cover your squash plants while the adult moths are out. You can cover your plants with a floating row cover or insect netting. This cover can be put on the right when you plant squash and you can leave it on until your squash plants start to flower. You can water through the covers. You can hold up the covers with PVC or small metal rings.

If your squash died last year do not plant squash there again. The vine borers will be in the ground and if you cover the squash plants, you are trapping the vine borer moths under the row cover with your squash!

If you have not covered your squash there are a few other things you can do. To see if you have the borers look at the base of your squash plants. Holes and orange goo at the base are signs that the vine borers are in the squash. You can try and cut them out by cutting an incision lengthwise at the base and then covering it with soil after you pull out the borer. There can, however, be multiple borers in one plant. You can also try to kill the borers while they are inside the stem of the squash plant. You can do this by taking clothespins or something sharp and stab into the side of the base of the plant.

There are other ways to deal with vine borers but we find growing squash they do not like or using a physical barrier as the most effective ways to deal with them.

Good luck with your planting!