I thought these were aphids the other day and finally decided to do an image search. I clipped some leaves that had eggs and newly hatched larvae, threw that specific zucchini away, and squished a bunch more. I also used some dead bug brew.
Ah, welcome to the club. They are the worst. There are nopesticides I’m comfortable with that work. Nasturtiums don’t help. I’m having some luck killing adults and crushing all the eggs, but there’s always some that survived. You have to do that weekly at a minimum. The only time I had any real luck was by skipping a year. But they’ll come back the year after you grow more squash.
Will diatomaceous earth work on them?
Not in my experience. Even if you coat the eggs and them directly.
I believe that diatomaceous earth works on all insects. It’s not poison; it’s finely ground silica, and it essentially wrecks their insect lungs. It will also wreck your lungs if you aren’t careful with it (silicosis is super-bad, m’kay?). The issue will be getting it where it needs to be to affect them, and you’ll have to re-apply after rain.
Actually diatomaceous earth isn’t silica - it’s fossilized diatom skeletons that works by physically cutting insects’ exoskeletons causing them to dehydrate, not by affecting thier lungs.
{Diatomaceous earth (/ˌdaɪ.ətəˈmeɪʃəs/ DY-ə-tə-MAY-shəs), also known as diatomite (/daɪˈætəmaɪt/ dy-AT-ə-myte), celite, or kieselguhr, is a naturally occurring, soft, siliceous sedimentary rock that can be crumbled into a fine white to off-white powder.](https://en.wikipedia.org/wiki/Diatomaceous_earth)
If you inhale it in significant quantity, you’ll end up with silicosis.
I hunt the adults and squish them when I water. It draws them out. Then I check every leaf for eggs. It is an effort to keep them out
