Insecticide treatments used against a rice bloodworm, Chironomus tepperi (Diptera: Chironomidae): suppression of larval populations

We assessed the effect of six organcyphosphorous insecticide treatments on larval chironomid populations in establishing rice. Treatments were applied to miniature rice bays (20 by 4 m) that contained heavy infestations of Chironomus tepperi Skuse-type larvae. Mud samples were taken immediately before insecticide application and subsequently at 3-d intervals for 15 d. Larvae were extracted by MgSO4 flotation. Chlorpyrifos (0.07 ppm), malathion (0.26 ppm), diazinon (0. 10 ppm), and temephos (0.05 ppm) provided highly effective control. Trichlorfon (0.38 ppm) and, to a lesser extent, chlorfenvinphos (0.22 ppm) were not as effective, allowing some larval resurgence 6 d after application. We consider trichlorfon at 0.38 ppm to be unsuitable for C. tepperi control