Spinosad products are not recommended for those insects categorized as "true bugs ".....squash bugs/stink bugs and all of their little relatives. Apparently, at least according to the reports that I read, Spinosad is simply not very effective against those types of sucking pests.

You would be far better off using neem, which acts as an anti-feedant and has growth regulator effects on plant eating pests. Neem is also very safe to use around beneficial species, as it requires ingestion for efficacy. When label directions are followed neem is a safe and effective plant protectant.

I'm still reviewing information about how spinosad works in plants but I do know that it is not systemic in the way you'd like it to be. It enters leaf tissues and moves from one part of the leaf to another but won't travel up or down the vascular system.

Injection works two ways....spinosad can kill certain insects by contact AND by ingestion.

When using ANY product on your plants, be sure that you read, understand, and follow the label directions.

Thanks, Rhizo. From what I understand, once spinosad dries on the plant, it does not kill on contact but only on ingestion, and therefore isn't dangerous to non-plant-eating bugs like bees.
I actually am searching for evidence that it is NOT systemic -- I'd think that if it for sure is not, then dribbling a little bit down the hollow part of stems (not intending it to get actually into the "circulation system" of the plant, just into the hollow space) would allow it to GET to borers inside the hollow vines (which would eat it and then die), but would NOT get into the zucchini fruit, nor would it get into the pollen and be dangerous to bees. I would assume it would not degrade as quickly as it wouldn't be exposed to sunlight, and therefore could be applied pretty sparingly - maybe even once.
SO if I were sure the stuff ISN'T taken up by the plant, I'd inject away!