Basic bio-ecological parameters of the invasive Red Palm Weevil, Rhynchophorus ferrugineus (Coleoptera: Curculionidae), in Phoenix canariensis under Mediterranean climate

Abstract

The invasive red palm weevil, Rhynchophorus ferrugineus Olivier (Coleoptera, Curculionidae), is one of the most destructive pests of palms in the world. Since its detection in the Mediterranean Basin, the ornamental Phoenix canariensis Hort. ex Chabaud has become its main host. This study was aimed at determining the life cycle of R. ferrugineus in live P. canariensis palms. Egg lethal temperature threshold and thermal constant were determined in the laboratory and resulted in 13.1 degrees C and 40.4 degree days (DD), respectively. A semi field assay was carried out in a mesh enclosure where living P. canariensis palms were artificially infested with neonate larvae at one-month intervals from June 2008 to May 2009 under natural conditions. Infested palms were dissected at different time intervals. Maximum mortality rates for R. ferrugineus were observed for palms infested either in December or January (100%), whereas those infested from April through September showed maximum survival rates. Mean monthly temperatures below 10.3 degrees C were lethal for neonate larvae, as 4.5 degrees C were for older immature stages. All recovered larvae could be classed according to one of 13 instars. A thermal constant of 666.5 DD was estimated for complete larval development. Pupal develoment required an additional 282.5 DD. Based on these results and on the temperatures from 46 climatic stations selected in the Iberian Peninsula, less than one generation per year can be expected in areas with mean annual temperature below 15 degrees C and more than two where mean annual temperature is above 19 degrees C.