Because all gardening is local


Time for emergency surgery!

All of the various squashes are prone to suddenly wilt and die, just when we think we will have a bumper crop. It’s all due to a reddish moth that looks like a wasp to the uninitiated, that has a larva (grub) that eats the inside of the squash stems.

Squash borer adult

Squash borer adult

If you see this mama flitting around your squash, be prepared for trouble!  And you can see that she’s already been there. Note the holes and the damage to the main stem.

Squash borer adult - closeup

Squash borer adult - closeup

She’s not going to hold still very long to get the camera focused, but here you see the coloration that identifies her as an adult squash borer.

Once you see damage on the stems, just above ground level, that plant is not long for the world, unless you intervene. Soon, as it munches away, you will see gelatinous pellets of frass alongside the hole. The larva is growing.

We are going to try to catch this one young. We hope we can save the plant.

Squash borer frass

Squash borer frass

So we will carefully slit the stem, parallel to its length. This won’t hurt the stem, at least not near as much as the borer will!

Careful cut to find squash borer

Careful cut to find squash borer

Found ya! You little parasite!  You are dead meat!

Found squash borer!

Found squash borer!

We’ve saved this plant. Time to cover the wound with some moist soil, so it can heal.

One can try a less intrusive form of surgery by poking a sharp toothpick or a stiff wire straight into the stem every quarter inch or so above the entry hole. But this poses a risk of missing the larva.

Here’s one that was too late to save; the borer has already eaten out all the plant’s plumbing, and has grown to large size.

Squash borer from killed plant

Squash borer from killed plant

The squash borer is a serious pest of all kinds of squashes. Some try to kill it with pesticides, but this is fraught with problems. You must kill the adult in the brief time it comes to lay eggs – or the freshly hatched egg just before it bores into the stem.

Once it is inside the stem, it’s pretty well protected. But using an insecticide on squash that is blooming may contaminate the nectar and pollen that feeds the pollinators. Kill the pollinators – and you bite the hand that feeds you!

So I would personally rule out pesticides for borers. Most years, you can get a harvest before the borers arrive.

Some use aluminum foil around the stem to either confuse or prevent the moth from egg laying. Some wrap the stems in pieces of old pantyhose.

One technique that I have used for vining squash is to cover the stem with dirt every couple feet. The plant will put out new roots at that point. If the main stem is destroyed by a borer, the plant will still live and produce from its alternative roots.

What has worked for you?

3 Responses to “Time for emergency surgery!”

  1. June 12th, 2011 at 8:11 am

    Jen says:

    These guys are my biggest garden problem! Excellent photos! Thanks so much.

  2. July 18th, 2011 at 8:51 pm

    Ann says:

    Yes, those photos really helped! We tried to do emergency surgery on our remaining three squash plants tonight after one perished yesterday. We only found the little squash borers in two of the plants. I’m not expecting the plants to survive, but I’m hopeful! The area near the roots looks bad but the rest of the plants are doing well. Perhaps it’s only a matter of time. Anyway, thanks!

  3. July 24th, 2011 at 12:27 pm

    Susan says:

    Thanks for the pictures! My zucchinis wilted overnight and I wasn’t sure the reason. After doing some research and seeing your pictures, I am certain there are borers after identifying some of the frass. Will attempt surgery today!

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