Determination of the most effective method for field establishment of biocontrol agents of the genus chilocorus (Coleoptera: Coccinellidae)

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Abstract
The coccinellid biocontrol agent Chilocorus nigritus (Fabricius) can be established on the non-target scale Asterolecanium sp. (Hemiptera: Asterolecaniidae) on giant bamboo Dendrocalamus giganteus. When these sites are adjacent to citrus orchards, the coccinellid readily moves across to reduce population levels of the target prey, red scale Aonidiella aurantii (Maskell) (Hemiptera: Diaspididae). C. bipustulatus (Linnaeus) and C. infernalis Mulsant are potential new biocontrol agents against A. aurantii in South Africa. Each life stage of C. nigritus, C. bipustulatus and C. infernalis has advantages and disadvantages for field introductions. This paper investigates different methods of introduction of the different life stages for field establishment. A number of synthetic materials were tested as egg pads for C. infernalis without success. Introduction of eggs adhering to stiff paper cards was unsuccessful and impractical for all species. Eggs, young larvae (first and second instars), older larvae (third and fourth instars) and adult C. nigritus were introduced into stands of bamboo. The adult was the most suitable life stage for establishment followed by older larvae, then younger larvae, with the least suitable being the egg stage. Adults of the three species were released on to scale-infested bamboo at two sites to evaluate the viability of such introductions and to compare their persistence at these sites. C. nigritus and C. infernalis persisted at one release site through the winter and the hottest period of the summer.