BIOLOGICAL CONTROL OF SCALE INSECTS ON CITRUS IN SOUTHEASTERN QUEENSLAND. II CONTROL OF CIRCULAR BLACK SCALE CHRYSOMPHALUS FICUS ASHMEAD, BY THE INTRODUCED PARASITE, APHYTIS HOLOXANTHUS DE BACH

Abstract

The introduced parasite, Aphytis holoxanthus De Bach, gave effective control of Chrysomphalus ficus Ashmead, in the absence of persistent chemical sprays during a detailed study in five blocks of oranges during 1975‐77. Scale infestations were reduced from 6.5 to less than 0.01 adult females per fruit within six to nine months of its establishment and were maintained at these levels for the remainder of the study. A twofold increase in scale numbers occurred where the parasite was suppressed on trees treated with DDT and a ten‐fold increase, where it was completely excluded by using gauze cages. A native parasite, Aphytis columbi (Girault), of lesser importance early in the study, declined in incidence after A. holoxanthus became established. A. holoxanthus established readily in 50 commercial citrus orchards in south‐eastern Queensland in which it was released during 1976. It reduced scale infestations in all of these orchards to economically unimportant levels within six to nine months. Copyright © 1978, Wiley Blackwell. All rights reserved