An improved iodine test based on the ability of the live scale to react with iodine, yielding reduced iodine products which in turn are unable to give the blue colour reaction with starch, has been used for determining the mortality of the California red scale after treatment with various insecticides. 0.1 % monocrotophos, omethoate or methidathion (active material) and 1.4 % ethion formulation were found to give good control, while methomyl, mecarbam and azinphos-methyl were less eflective. The results obtained by the iodine method resembled those obtained by the visual method, commonly used for determining death in armoured scales.