Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Rhynchophorus ferrurineus and Paysandisia archon, two exotic insect pests harmful to palm trees.

Abstract

The red palm weevil (Rhynchophorus ferrunneus Olivier, 1790) (RPW) and the Castniid palm borer (Paysandisia archon Burmeister, 1880) are two exotic species that arrived in Europe at the end of the last century with imported ornamental palms. The moth is native to South America and completes one generation annually or, under adverse conditions, biannually. The cespitose palm, Trithrinax campestris, is the preferred host of the moth, but other ornamental palms such Chamaerops humilis, Howea forsteriana, Phoenix canariensis, and Washingtonia spp. are also good hosts. The debilitating effect of moth infestations predisposes these palms, especially P. canariensis, to parasitization by the RPW, an invasive species native to Asia and able to attain 2-3 generations annually. Both species of insects are regulated in EPPO countries and are included on list A2. In Italy, they are kept under specific mandatory control programs. The suppression of the populations of the two pests is very challenging due to the absence of effective natural antagonists, the cryptic parasitic habits of the larvae that are difficult to locate inside the frond, the lack of early and noticeable symptoms of decline in the infested palms, and the abrupt and sudden collapse of fronds, occurring in the late phase of the insect infestation when no effective management measures can be implemented. The chemical management of these two pests does not have a long term persistent effect. It is also expensive and environmentally unsafe. Many chemicals registered for use against moth larvae pests on flowering ornamentals and forest trees are approved also for the control of the Castniid larvae infesting palms. However, repetitive applications of these products are necessary due to the long ovideposition period of the insect. Four chemical are registered for the control of RPW, but their label expires on December 1, 2011. The mandatory removal, grinding and disposal in landfill of the palms infested with both pests are useful and effective precautionary practices to eliminate sources of insect infestation and to suppress their population levels in infested areas.