Resistance to some carbamate insecticides ( methomyl and carbaryl) in H. armigera is has been known since 1983. But at that time no resistance to thiodicarb (also a carbamate) was identified. However, in early 1993, there were severe H. armigera control problems with thiodicarb in sweet corn and maize crops. These failures were widely distributed across New South Wales and Queensland. Testing at Tamworth showed that these populations were resistant to thiodicarb (approximately 30 fold). In some, the resistance frequency was as high as 80%. 1hiodicarb resistance conferred cross resistance to other carbamates (such as methomyl). While thiodicarb resistant H. armigera were largely confined to the maize and sweetcorn populations, a resistance survey on cotton in early 1993 indicated that a low frequency (-10%) of thiodicarb resistant individuals were also present in the cotton areas of NSW and Queensland