A synergistic herbicidal composition containing (a) a compound of formula (I): or an agriculturally acceptable salt or ester thereof and (b) an imidazolinone, including but not limited to imazethapyr ammonium, imazamox ammonium, imazapic ammonium, imazapyr isopropylamine salt, imazamethabenz-methyl and imazaquin isopropylamine salt, provide control of undesirable vegetation e.g., in direct-seeded rice, water-seeded rice, transplanted rice, cereals, wheat, barley, oats, rye, sorghum, corn or maize, sugarcane, sunflower, oilseed rape, canola, sugar beet, soybean, cotton, pineapple, vegetables, pastures, grasslands, rangelands, fallowland, turf, tree and vine orchards, aquatics, plantation crops, vegetables, industrial vegetation management (IVM) and rights of way (ROW).