I haven't had any instance where my bud had any chemical taste or flavor that I could detect, but if you are really concerned, you could wash your bud off with some water. THC and other cannabinoids are only minutely water-soluble, so it wouldn't decrease the potency of your bud in any noticeable way. Most pesticides, fertilizers etc. are water soluble, so the rinsing should help wash off anything that might be present. Make sure to use cool water (I wouldn't advise using soap or detergent, might have some bad effects), hold a bud under the water for a few seconds, turning, and if desired, prodding the bud to have better penetration of the water. Lay on a paper towel, and put in a dry, sunny place. Voila!

If you have exceptionally dry bud, try moistening it up a bit first with a bit of wet paper or small fruit peel in your stashbox, only for a little while- you don't want to encourage bacterial or mold growth. If you rinse it after the bud is a bit springy, it will be a bit easier for you to maintain the flakier, drier pieces of bud, if you have any.