Can azadirachtin deter red palm weevil, Rhynchophorus ferrugineus, (Coleoptera: Curculionidae) from laying eggs?

The Kingdom of Saudi Arabia is among the top three date producing countries of the world accounting for 17% of the global date production. Red palm weevil (RPW) Rhynchophorus ferrugineus is a key pest of date palm in Saudi Arabia where the annual loss due to eradication of severely infested palms could run into several million dollars. Infestation due to RPW begins when adult female weevils lay eggs on palm tissue that hatch into larvae which bore into the palm. Female weevils are particularly attracted to palm volatiles that emit from fresh cuts/wounds on the palm which occur during frond and offshoot removal.

Currently RPW is managed in the Kingdom employing a pheromone based Integrated Pest Management (IPM) strategy where the use of insecticides for preventive and curative treatments is imperative. Chemical-free/organic date palm plantations are increasing in the Kingdom where bio-pesticides are important for the management of RPW and other insect pests. We studied the extent to which egg laying by RPW could be deterred using azadirachtin treated sugarcane pieces in ‘choice’ and ‘no-choice’ assays in the laboratory.

In the choice test, female RWP weevils preferred the untreated host for egg laying, with 1.0% azadirachtin recording the maximum oviposition deterrence of 96.35 %.

In the no choice test female RWP weevils laid eggs, both in the host and also outside the host. 1% azadirachtin exhibited the highest oviposition deterrence where 85.99 % of the eggs were laid outside the host. Thus, treating fresh wounds of palm tissue with 1% azadirachtin would significantly deter RPW from laying eggs.