Armyworm (Mythimna loreyi and M. loreyiminw) infestation of Queensland sugarcane ratoon crops were observed during spring 1989, and the effects of chlorpyrifos treatment (0.5 kg/ha a.i.) assessed. Treatment effectively stopped armyworm activity, but had no effect on yield on 10 out of 11 sites. Treatment may, however, prevent yield loss due to the increased susceptibility to flood damage of artnyworm-infested crops.'Tbere was only a single infestation of the crop. Tachinid flies (Tritaxys milias, Cuphocera javana) and an ichneumonid wasp (Lissopimpla e-rxelsa) were parasitic on the armywortns; they may contribute to the lack of later infestations, and are probably depleted by insecticide treatment. M. loreyi is recorded in Australia for the first time. none