Salvaging the Squash

I've been good at photographing in the garden the last few weeks, just not on uploading.

One of the recent battles has been against the squash vine borer. Actually, I battle these every year, but this time I tried taking a more proactive approach on the problem. I also planted enough vines this year that I could afford to lose a few in case some of the treatment recommendations didn't work.

So what's a squash vine borer? In short, it's the larvae of the Melitta curcurbitae moth. The moths lay eggs on the vine, the larvae hatch and burrow into the stem to then feed on the stems. There are plenty of good Extension publications available on the topic, such as this one from Minnesota and this one from Georgia.

Here was the first clue of a problem in my garden. See the healthy zucchini plants in the foreground and background, but one wilting in the middle?

The wilting is most obvious in the middle of the day, with the plant recovering in the evening when the sun goes down. Now why would only one plant wilt when the others around it are fine??

Upon closer inspection of the squash stem I see the tell-tale frass (larvae poop).

arrows pointing to frass and signs of damage

 The next step is to break out the knife and make a long cut into the stem.

Yup, more frass

Why, hello there, troublemaker!

And he has friends!

Lovely.

So what are the options? Obviously, they must die, which is why it's handy to have a knife in the garden. I call it a "squash borer-ectomy" as I carefully pick out the little suckers and then squish them. I opened up the incision a little further in each direction until I got to healthy stem tissue that is free of burrows and frass. In this plant I found three, another plant had five.

As a precaution I then smothered the stem in Sevin garden dust. The tricky part is also getting it on the underside of the stem so that other borers are killed before they get a chance to set up camp inside the stem.

Several publications recommend covering the cut part of the stem with soil so that the plant can send out auxiliary roots around the wound site. These auxiliary roots will then provide nourishment to the rest of the plant, and the damaged section could be cut out altogether. Ideally, the plant will continue to live and produce more tasty zucchini or summer squash.

Two problems with this. First, the way my plants developed this year the stem barely made contact with the ground before it spilled over the side of the raised bed. Getting auxiliary roots to take hold was a challenge. Second, that was about the time that the summer heat set it, which means all plants slowed down on their productivity, not just the damaged ones.

So was it successful? That depends on how you measure success. From the plant in the pictures I was able to harvest a couple of squash that were half-developed at the time I intervened. The other plant, which did not have as well developed of a stem to begin with, had one half-developed zucchini which never got any bigger. A couple weeks later I ripped out those two plants when they quit producing new blossoms. They never did produce fruit beyond what was already on the vine when I tried removing the borers. With a half-dozen other plants in the garden it wasn't worth it to keep nursing these along.

How do I prevent this in the future? Sadly, squash borers are fairly common in this part of the country. The other healthy plants have been getting preventative treatment with Sevin dust along the stem. The plants that get removed go on my "trash pile" - bad idea to compost any plants that are diseased or harbor insects. This is especially important when the life cycle of the squash borer includes pupating in the ground before hatching the adult moth.

In the meantime, I'm still producing enough zucchini and yellow squash to keep myself and a few co-workers well fed. After all, if you can't produce a bumper-crop of zucchini, can you even call it a crop?