I can't tell you for sure if this will not wash off trichomes, but I use a 1 part isopropyl alcohol to 2 parts water a dash of soap solution to ward off pests. Test the solution on part of plant and if no bad results, apply a couple times a week. Probably won't totally get rid of pests, it never has for me, but it definatenly cuts back on their popluations. Good luck, too bad its happened so far into flower, but this is one of the most eco-friendly solutions I can think of