Chemical and integrated control of the long-tailed mealybug, Pseudococcus longispinus (Targioni-Tozzetti) (Hemiptera: Coccidae) in the Riverland of South Australia

Abstract

Chemical control of the mealybug Pseudococcus longispinus (Targioni-Tozzetti) was most effective if sprays were applied when the mealybugs were in the dispersive crawler stage and when the host plant afforded the least shelter. A two-spray program with sprays applied in August and late November effectively controlled a dense infestation of the mealybug on citrus. Red scale (Aonidiella aurantii (Maskell)), the major insect pest of citrus, was also effectively controlled.

An overall pest management program has been developed for citrus in which all insect pests are controlled by combination of natural enemies and insecticides as required. Outbreaks of the mealybug, and other secondary pests, are controlled by sprays of aminocarb or methomyl. These two insecticides prevented the population resurgence of mealybugs in the subsequent generation which occurred when maldison was used. Bioassays showed that aminocarb and methomyl were toxic for less than a week to the mealybug and to parasites and predators, whereas maldison and methidathion were toxic to the parasites and predators for about a month. Parasite pupae inside the host mealybug survived sprays of maldison and aminocarb. It is suggested that natural enemies emerging after spraying, from resistant or protected stages, survive sprays of aminocarb and methomyl but not sprays of more persistent insecticides like maldison; and that these survivors continue to suppress populations of their hosts. Hence aminocarb and methomyl are probably specific in their action against the mealybug and the other secondary pests of citrus because of their short persistence.

An insecticide check experiment failed to demonstrate that natural enemies significantly reduce populations of the mealybug. Possible reasons for the failure are discussed.