The problem I’ve had with the only applied stuff I’ve used, diatomaceous earth (I haven’t used organic controls like BT or pyrethrin or rotenone), is that you have to keep using it. This also takes time and costs, and could do as much harm as good eventually, because they’re not too selective. Like, DE kills off beneficial bugs, including non-hard bodied, like even bees, so if you’re dumping a fair bit of it on to kill a CPB invasion, you could be causing other problems. Like, I believe ladybugs eat CPB eggs, and DE will kill ladybugs… (Coincidentally, a comment just appeared on another post, also about CPBs, and asking about ID-ing CPB eggs vs ladybug eggs in order not to kill off ladybugs…)

It sounds like you’re sticking to organics and as low-impact methods as possible, so you should read up on the CPB life cycle, and next year at least, try to get craftier with timing, like getting the eggs when they come out (spring and again once or twice a season), or shaking the larva off when they’re small, and maybe some sort of trap crop…

When you’re having a big problem, chemicals can sound easy…! Luckily, I haven’t run into a BIG one that couldn’t be solved otherwise…so far!

I tell you, I’ve been hand picking those CPBs off for over a week now and have to do it every few hours.  I go out about 4 times a day and can pull off another 20 or so.  I’ve removed a whole entire jar so far.  It’s tedious and takes a lot of my time to do it.  

I can’t tell if the babies can’t get back up the stalk, but from what I’ve read, they a born near the soil, but they seem to cluster in groups.  I haven’t found any eggs at all, but lots of larvae.  The Bt seems to work on the babies - give it a few days to work, and there seems to be fewer babies today.   It’s funny, a few years ago, eggplants was one of my best harvests - easy and fruitful.  Not this year!

For cucurbits (cukes, squash, etc), I tried at the same time, with even less success. I guess it depends on the weather and the pest level. The cucumber beetles fly around a lot, so the chances of hitting ‘em seem lower. Then it’s a matter of how long the DE remains on the leaves. I’ve had leaves almost white with DE (an experiment), and still had CBs…

As for most things, for diatomacous earth, I guess your mileage varies…

I don’t know if sulfur powder will kill Colorado Potato Beettles, but we had a really bad chigger problem about June and five pounds of Sulfer dust at dawn seemed to wipe them out of the tomatoes in one day!

I wondered where the CPB were coming from, because they were there from the first season we had a garden there, then I found them in the horse pasture eating on wild night shade plants… they just had to migrate about 100 yards to get to the potatoes.