I've found that IF you catch it early, just washing the plants off with the hose early in the morning will do the job. I've tried the milk, but that didn't work well for me. Dr. Bonners peppermint soap (1Tbsp per quart or 4 Tbsp per Gal of water) not only killed the thrips I was spraying for, but killed all the mildew AND rust on my roses, but it does leave a residue if you don't rinse it off after a couple of hours.