Clash Post Emergent Herbicide 2.5 gal. (Dicamba). Clash controls difficult ALS- and triazine-resistant annual weeds in addition to a broad spectrum of perennial and biennial weeds. And with its wide application window, Clash gives you the convenience and flexibility to deal with unpredictable spring weather. Clash is labeled for a variety of sites from crop protection to vegetation management to provide use-flexibility no matter the market.