Edit 7/10/2022: A lot of people find this post every year, when the squash vine borer is around. This post is years old. Let me summarize where things ended up:
- Read Post #G27 for a summary of everything I found out about squash vine borer (SVB).
- Spraying spinosad solution (0.008%) onto the stems of my summer squash every five days worked fine. Kept the borer out, didn’t kill the bees. And it’s a short-lived non-synthetic poison, so it should generate minimal collateral damage. (E.g., won’t (or shouldn’t) build up in soil or fruit, run off and kill fish, or any of that. ) But that’s a lot of work, particularly given that the borer is around (in this climate) for eight weeks or so.
- For 2022, I’m trying a completely different approach. I’m growing varieties of squash that don’t need to be pollinated (“parthenocarpic” varieties, Post G22-013). I’m growing them inside an insect-proof hoop house to keep out the vine borer. As of July 2022, that seems to be working OK. But I started those late, and I still haven’t harvested any squash yet.
Edit 7/24/2024: In the end, growing summer squash under netting, in my back-yard garden, was just too much hassle. And I didn’t get much yield. So this year I skipped the summer squash. Instead I’m growing what are supposed to be close substitutes: Tromboncino (a winter squash) and guinea bean (an edible member of the gourd family). These are solid-stemmed vines that, by reputation (and based on my experience this year), are not bothered by the SVB.
I can attest that immature (foot-long) trombincini fruits are an excellent substitute for zucchini. But the yield seems poor, relative to zucchini or yellow summer squash. It’s the end of July, the vines are huge, and so far I’ve picked two tromboncini, and the guinea bean has only started to set fruit. Maybe they’ll pick up the pace in the heat of August? But I’m not betting on it. I’m guessing the low yield makes sense, else we’d all have been planting tromboncini instead of summer squash all along.
The original post follows.
I’ll try to avoid my usual TLDR style and get to the point. A later section adds more detail.
I’m not going to try to get systemic protection using a neem “soil drench”. Maybe I am going to use neem oil as a horticultural oil spray, hoping to smother the eggs. But I am reluctant to do that, as nobody seems to be able to pin down why, exactly, neem oil should work against the SVB. And even for a relatively harmless poison like raw neem oil, I’m reluctant to spray that in volume around my garden, when I really have no clue what it’s supposed to be doing for me in this case.
Details follow. Continue reading Post #G10: Squash Vine Borer: Thinking through neem and considering horticultural oil?
Credit: Mother Nature.