BIOLOGICAL CONTROL OF SCALE INSECTS ON CITRUS IN SOUTHEASTERN QUEENSLAND. I CONTROL OF RED SCALE AONIDIELLA AURANTII (MASKELL)

SUMMARY The parasites, Aphytis lingnanensis Compere and Comperiella bifasciata Howard gave effective control of Aonidiella aurantii (Maskell) in four blocks of oranges during 1975‐77. Scale infestations in the blocks were reduced to the economically acceptable level of less than 0.05 adult females per fruit in 12 months and were maintained at these levels at harvest in 1976 and at conclusion of the study prior to harvest in 1977. Large numbers of scale developed on trees where parasites were suppressed by treating with DDT and a similar increase was demonstrated where parasites were excluded using gauze cages. Persistent chemical sprays suppressive to parasites were not used in the blocks during the study and it is considered that effective parasitic regulation can be realized only if such sprays are avoided.