The release of Plectonycha correntina, a leaf feeding beetle for the biological control of Madeira vine

Madeira vine, Anredera cordifolia (Ten.) Steenis (Basellaceae) is a South American perennial vine that forms dense mats over trees and shrubs. It is a major environmental weed of coastal and sub-coastal areas in Queensland and New South Wales and it poses a significant threat to biodiversity in riparian, sclerophyll and rainforest communities. The South American leaf-feeding beetle Plectonycha correntina Lacordaire was approved for release as a biological control agent in February 2011. The beetle was subsequently mass reared and introduced into madeira vine infestations in south-eastern Queensland from May 2011 onward. Both adults and larvae of this insect are leaf feeders, with larvae being particularly damaging. Post release field monitoring determined whether the beetle had established, the rate of spread from the initial release site and level of damage. Field observations at 29 sites where releases had been made before winter (6100 beetles in total) were made in October 2011. The insect had successfully overwintered at 51% of these sites, with adults, larvae and eggs being recorded. Post-winter releases of another 20 462 beetles over 72 sites in south-eastern Queensland, five in northern NSW, one in Central Queensland and two in Far North Queensland are also indicating promising results with insects being present and reproducing at 42% of sites in the following autumn. Damage levels at all sites were generally low, reflecting that this was the first year of releases, but 20% loss of leaf area was estimated at two sites. Preliminary analysis of data indicated that establishment does not appear to be closely related to the number of insects released, so other factors such as season of release, light levels or density of predators may be important.