I have used malathion and it mostly worked but is really stinky for quite a while. I had a couple of paphs that had scale hiding this spring. I decided to try a systemic this time. I treated with Bayer 3 in 1 for roses once a month all summer while my plants were outside. Those with scale the worst are starting to come back really well. I have noticed no more scale since bringing them in for the winter. Good luck.