Of a range of insecticides evaluated in field trials for control of thrips on onions methomyl, malathion and phenthoate showed consistent effectiveness. Duration of insecticidal activity was short and only 10–14 days after application a rapid increase in the nymphal population occurred. For successful control of thrips on late transplanted onions initiation of spraying programmes was indicated when the level of infestation reached 5–10 nymphs per plant.