Australian ladybirds used in biological battle

The cottony-cushion scale bug Icerya purchasi is a serious menace to the indigenous flora of the Galapagos islands. It has no natural ennemies and has greatly proliferated since its introduction in the archipelago in 1982. It has already attacked 31 species of endemic plants, of which 16 are considered as endangered species by the IUCN, and has also a negative effect on other local insects which feed on these plants. In particular the micro ecosystems of the white mangroves which harbour a multitude of highly specialized life forms are severely damaged by the cottony-cushion scale bug. These mangroves are also home to the mangrove finches which are an endangered species. With the disappearance of the white mangroves the 100 or so surviving mangrove finches would lose their nesting ground.

The cottony-cushion scale bug cannot easily be controlled by chemical methods but in other places (California) the introduction of its natural enemy the ladybird Rodolia Cardinalis has been very successful. Since releasing a new species into such a fragile island ecosystem can cause great damage to the local flora and fauna it was important firstly to examine what effect releasing the ladybirds would have on the island wildlife. The results of the researchers of the Charles Darwin Research Station showed that the ladybirds do not affect any other non-vertebrates. Equally it could be shown that the local insect-eating vertebrates such as Darwin finches and other small birds avoid the ladybirds and therefore are not harmed by them. This action was accompagnied by a major campaign to inform the local population about this first deliberate introduction of a new species of insect. At the same time farmers and school children were trained in workshops so that they could participate in the release of the ladybirds and in the supervision of the project.

The ladybirds were bred by specially trained persons from the Research Station and the National Park and firstly released in high priority regions. These regions were chosen as having a high density of endangered plants affected by the cottony-cushion scale bug. The releases are accompanied by intense field observations to control the effectiveness of the project and to have a detailed study of the effect of the ladybird release on the fragile ecosystem. At the end of the project a detailed measure of its success will be established as well as a cost-effectiveness study of the ladybird release. The results of the biological control in the Galapagos of the introduced pest I.Purchasi by the ladybird R.Cardinalis will be published locally, nationally, and internationally.

The aim of this project is to obtain biological control of an introduced pest in order to protect native plants. Since the cottony-cushion scale bug has until now proliferated unchecked, rapid action is important for the success of this project. Therefore, in 2002, 1365 ladybirds were released on the islands of Santa Cruz, San Cristobal, Isabela, Floreana, Fernandina and Pinta. The first results are clear, the number of cottony-cushion scale bugs has diminished...

The Swiss Friends of the Galapagos Island have supported the project in 2002 with the sum of CHF 11'100.