The presence of three fortuitously arrived insects have an impact on invasive alien plants in Spain
The populations in Spain of the invasive alien plants Opuntia maxima (Cactaceae), Azolla filiculoides (Salviniaceae) and Agave americana (Asparagaceae) have been noted to be damaged by the fortuitously arrived insect species: Dactylopius opuntiae (Hemiptera: Dactylopiidae), Stenopelmus rufinasus (Coleoptera: Curculionidae) and Scyphophorus acupunctatus (Coleoptera: Curculionidae) respectively. These insects have different impacts and spread at different rates.
D. opuntiae has progressed at a rate of 30 km per year since 2009, leading to the local extinction of O. maxima. The local government of Valencia has started to use this insect for the control of the local infestations of O. maxima, located in the coastal sandstone natural park of Calderona and Espadán. Observations showed an initial expansion rate of the insect of 5 m per month with evidence of clear visual damage (chlorosis and necrosis) within 6 months.
S. rufinasus has colonized 6 wetlands in less than 1 year along a coastal strip of 80 km and curbed A. filiculoides populations from 16 occupied ha to a small residual presence.
S. acupunctatus shows a lower rate of dispersal despite the flying ability of the adults, but the mortality of infested Agave americana plants is high. This species was formerly registered on the EPPO Alert list and has recently been detected in Cyprus (see EPPO RS 2014/087)
Sources
Deltoro V, Torres C, Pérez P, Jiménez J (2014) Dispersal, impact and use of the three fortuitously arrived parasites in the control of invasive exotic plants in Valencia. Abstract of the 4th International Symposium on Environmental Weeds and Invasive Plants, Montpellier (FR), 2014-06-19/23.