Studies on curative treatment of red palm weevil, Rhynchophorus ferrugineus Olivier infested date palms based on an innovative fumigation technique

The Red Palm Weevil (RPW) Rhynchophorus ferrugineus Olivier (Coleoptera: Curculionidae) is a key pest of date palm Phoenix dactylifera L. in the Near East and North Africa region.RPW infested date palms respond to curative chemical treatments if detected and judiciously treated in the early stage of attack.However, the currently used curative treatments, involve either excessive tissue removal of the palm around the infested palm section (mechanical sanitization) making the palm weak and vulnerable to toppling, injecting insecticide into the infested palms which often does not kill all the stages of the pest within the palm, calling for repeated applications or fumigating the infested palm section with phosphine gas which is also not always effective, possibly due to inadequate dose and escape of the gas.A new fumigation technique involving treatment of infested date palms with aluminium phosphide tablets (3g) ensuring complete entrapment of phosphine gas was devised and field tested in 295 RPW infested date palms in various stages of attack in Al-Qassim, Kingdom of Saudi Arabia, during 2017-2018.The technique was tested in both young date palms (9-12 years old) as well in offshoots (4 years old), through a series of field trials to optimize the number of applications, dose, duration of treatment and type of wrapping to entrap the gas.Results revealed that for young date palms in the susceptible age of attack to RPW, a single application of 10 aluminium phosphide tablets for 5 days inserted in air tight black plastic wrapping resulted in complete mortality of larva, pupae and adult stages of the pest.Further, in offshoots, a single treatment with 15 aluminium phosphide tablets inserted in air tight transparent plastic wrapping for 10 days ensured complete mortality of the pest within the palm.The technique can be used for both field treatment of infested palms as well for quarantine treatment of date palm offshoots and is gaining popularity in Saudi Arabia.