Yesterday I discovered ants making themselves at home in my bay tree. Just the little sugar ants, not the big red ants we often have issues with around here.
I've successfully used tobacco tea on about everything. CAUTION: Using nicotine is essentially a carpet bombing operation. It works on anything with a nervousystem, even beneficial things like bees and ladybugs and earthworms. I recommend isolating the plant away from everything else when doing this. I've seen no evidence that it's harmful to microbial life.
Just a heaping spoonful of the cheapest tobacco you can find soaked overnight or steeped hot to a quart or so of water, add a few drops of alcohol to kill any virus or what not that could possibly be transferred to other plants, and a couple drops of dish soap as a surfactant. Strain it to get the chunks out- I use a coffee filter. Use a spray bottle to apply to the above ground parts of the plant, and then water the soil with it too to get anything that might be living in there.
I sometimes do it when my tropicals come in for the winter, and again before they go out in spring, and occasionally in between if I discover I missed something. I also toss a few cigarette butts in my rain barrels on occasion to keep mosquito larvae from thriving in them, or sprinkle just the straight dry tobacco on the top of the soil so it works there when I water.