A little over a year ago, I wrote a post about an insect pest whose behavior seems against its self-interest. The unanswered question in that post was "why do cutworms cut down (and therefore kill) the young plants they feed on?"
Today, I'm asking the same question about squash vine borers (Eichlinia cucurbitae).
A squash plant will go from looking like this...
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| (Unfortunately, I don't have a "before" picture of the plant in question, so I had to settle for a picture of the one growing in the same hill.) |
...to looking like this in a matter of hours.
I've tried really hard to take care of my squash and pumpkins this year, making the rounds twice a day to check for and remove any squash bugs or squash bug eggs that I find. And as I make my rounds, I try to check for signs of the squash vine borers and their eggs.
I thought I was doing a good job. I hadn't seen any signs of frass coming from the stem on any plants, including the one in the picture.
But when I looked out the window at the garden this afternoon and saw one of the plants wilting much more than would be expected in the afternoon sun, I knew what was causing it. The plant seemed fine this morning.
Obviously, I wasn't doing as well at detecting the pests as I thought.
From past experience, I know that once the plant wilts, it can't be saved. So I just got my box cutter, cut it off at the base, and pulled the rooted part out of the ground.
The damage is always extensive and absolute. And looking inside the stem, one can see why the plant won't survive. The insides are nothing but mush. The poor plant has zero chance once the borers are inside for any length of time.
So again, I find myself asking, "Why they do this?!!!!"
What does the moth benefit by killing the plant it depends on before the plant has even had a chance to produce seeds?
I've harvested seven yellow squash this year, and was looking forward to having more. After today, I'm wondering if the other plants will be wilted later today or tomorrow.
Because squash vine borers have become such a problem for me, I actually planted a second and third round of seeds. The plant that died today was from the second planting. The third ones just came up a couple of days ago. Maybe those plants will be growing in the window of time when the borers aren't active? I hope so.
When the shade gets over the garden this evening, I intend to try to dig down to find the pupa. I expected it to be buried down in the soil under the plant, but didn't see it when I scratched around in the dirt. I probably didn't dig down deep enough, or maybe didn't go out far enough from the plant.
But if I find it, I will very gladly smash it with my boot. And as it sees my boot coming down on it, I hope it is thinking, "Why she do this?!!!"
Update 6/21:
I never did find the chyrsalis of the caterpillar that killed my squash vine. But I found several eggs on the squash yesterday and today.
Those were scraped off and squished between my fingers.
And I noticed several leaves with frass coming out a hole near the top of the stem. I cracked the stems open and found the nasty little caterpillars.
I stomped them with my boot.