Screening Date Palm Cultivars for Resistance to Red Palm Weevil,Rhynchophorus ferrugineus(Coleoptera: Curculionidae)

Abstract

Date palm, Phoenix dactylifera L. (Arecales: Arecaeae) is the most important crop of the Arabian Peninsula. The Kingdom of Saudi Arabia is among the top 3 date producing countries of the world estimated to have over 400 date palm cultivars of which 25 are important and yield 1.3 million tons of dates annually. The red palm weevil (RPW) Rhynchophorus ferrugineus (Olivier) (Coleoptera: Curculionidae) is a key pest of date palm in the Middle East. We studied the mechanisms of resistance against RPW in 7 major date palm cultivars of the Al-Ahsa oasis in Saudi Arabia viz. ‘Khalas’, ‘Sheshi’ , ‘Reziz’, ‘Khasab’, ‘Hatmi’, ‘Shahal’ and ‘Gaar’ by determining the extent of attraction of female RPW adults to fresh palm volatiles emitted from date palm frond tissue through four-arm choice olfactometer assays. Further, we assessed the degree of antixenosis and antibiotic effects if any by evaluating the number of eggs laid (oviposition), per cent egg hatch and larval tunnelling in these cultivars. Results revealed that the popular date palm cultivar ‘Khalas’ had the least antixenotic effect on female RPW adults where a high degree of attraction to palm tissue volatiles was recorded, which was statistically similar to the cultivars ‘Reziz’, ‘Sheshi’ and ‘Hatmi’. The cultivars ‘Khasab’, ‘Shahal’ and ‘Gaar’ exhibited high degree of non-preference (antixenosis). Further, ‘Reziz’ registered the highest egg lay by RPW and was statistically onpar with the cultivars ‘Khalas’ and ‘Sheshi’. Similar and non-significant values for egg hatch and larval tunnelling in the cultivars tested indicate no antibiotic effects against RPW in the 7 date palm cultivars. Since over 50% of the area in the Al-Ahsa oasis is under the cultivar ‘Khalas’ with several new plantations in the susceptible age of less than 20 years, RPW is likely to pose a major challenge to date farmers of the region in the years to come.