Yes, sulpher dust can act as an insecticide. You can spray micronized sulpher that is in a water solution and spray only in the early a.m. hours when less beneficials are present. Or dig up the disease magnets and go no spray. That's the easiest and best option for a lot of reasons, including the fact that I'm too lazy to suit up properly to spray.

HollySprings, are you sure it can act as an insecticide? It is a miticide, but I don't know that it is an insecticide. I just ran a couple of searches and didn't find anything of substance other than a repeated claim that it was used as an insecticide by the ancient Egyptians or Sumerians. One page suggested to me that what the others were talking about was the use of SO2 as a fumigant, and of course SO2 is not sulfur any more than water is hydrogen gas.

Helen, if your aphids are declining this time of year, the ladybugs will have left voluntarily in search of richer pastures. Could that be it? I use sulfur, and I had plenty of ladybugs when I needed them.

It's not a very potent insecticide, but regular sulpher as a dust and not a micronized spray, yes, it's an insecticide. From what I understand, it works by blocking the breathing pores on the insects body. The same principal as using flour on aphids almost. And that's why as a dust it will have some residual insecticidal properties unless it rains it off.