Press Releases

Preliminary data reveals effectiveness of biological control in Galapagos

Puerto Ayora, February 8 th 2010 –

An Australian ladybird on the Galapagos Islands is succeeding in controlling the invasive cottony cushion scale (Icerya purchasi), according to results of work carried out by scientists Mark and Christina Hoddle of the University of California, Riverside, and Roy Van Driesche of the University of Massachusetts, Amherst, in cooperation with Charlotte Causton, adjunct at the Charles Darwin Foundation, CDF staff, the Galapagos National Park Service, and the Galapagos Inspection and Quarantine System (SICGAL) during the last three months of 2009.

While work is still ongoing, data collected during the first phase of the study suggest that the mariquita or Vedalia beetle, an Australian ladybird (Rodolia cardinalis) has survived and spread, while suppressing the cottony cushion scale on many native Galapagos plants, including the white mangrove, Acacias, and Scalesia. However, there are several plant species still being affected by the scale, and further study is required to determine why the mariquita is not effective on these host plants. In addition to being effective, the project has been safe, as no evidence from field observations or the large cage studies was found of attack by R. cardinalis on non-target insects.

Infestations of the cottony cushion scale damage plants restricting their growth and can even kill them by sucking plant sap. Their sugary waste also attracts invasive ant species that guard the scales from predators and thus augment the problem. The problem is particularly critical for threatened species with restricted range as it can lead to their extinction.

The scale was first discovered in the Galapagos in 1982, and has spread to at least 15 different islands in the archipelago. It has infested at least 62 native or endemic plants, 16 of which are on the IUCN Red List of Threatened Species.

A Technical Advisory Committee constituted by the Charles Darwin Foundation and the Galapagos National Park Service recommended biological control with the Vedalia Beetle. Following intensive testing to ensure that the beetle would only eat the scale insect and approval from the quarantine service following regulations to ensure that all risks had been minimized, it was first imported in 1999 and released to 10 different islands in 2002.

Biological Control programs aim to reduce pests such as the cottony cushion scale through biological control agents, like the Vedalia beetle, that only attack the species needing control. The biological control agent comes from the native range of the invasive species. Biological control does not lead to invasive species eradication. Instead the control agent maintains the target species at a level so that its impact is reduced.

This initial evaluation, which will continue through 2011, is the first to measure project success. Results show additional reasons for optimism, as the Vedalia Beetle not only survived on the islands on which it was released and reduced the cottony cushion scale on them; it has also tracked its target to other islands.

This is the only biological control agent introduced to date to Galapagos to help combat the growing number of problems from invasive species. We are excited by these results, and hope that this will open the door for the use of the technique to help in the control of species that are impossible to eradicate, and whose control is prohibitively expensive.

More details of this project are available on the website http://www.biocontrol.ucr.edu/rodolia/rodolia_icerya_biocontrol_galapagos.html

For more information, please contact Alex Ontaneda (alex.ontaneda@fcdarwin.org.ec).