The role of natural enemies in controllingIcerya purchasi in South Australia

The obscure occurrence of the cottony-cushion scaleIcerya purchasi Maskell in its native country Australia is generally attributed to its natural enemies. Twelve natural-enemy-exclusion experiments were conducted at monthly intervals to confirm the role of natural enemies. Each experiment had uncaged, open-caged, and caged treatments. The natural enemies were active throughout the year. The percentage of scales surviving to adults in the cages was significantly higher than in the open-caged treatments, except the April (first) cohort. In both open-caged and uncaged treatments, the percentage of scales surviving to adults was similar and matched the changes in the numbers of natural enemies, thus confirming their importance in controllingI. purchasi in South Australia.