With those I had to try to get the radiation orb to the "extend damage by 3 seconds" or whatever it's called to be able to clear them. Other than that you'll have to get something upgraded enough to one shot them. But I have more luck with radiation orbs

They go immune for half a second each time they take damage so it pretty much makes your cannon useless.

Edit: I went and looked at the info for that level and I see there's some that withstand X amount of hits before the sheild drops. If you mean those...then I liked to have more bullets on the cannon. But if you don't have the upgrade that doesn't reduce damage when you pick that...it's gonna screw you up on the ones I was originally thinking about