Status of pheromone trap captured female red palm weevils from date gardens in Saudi Arabia

Date palm, Phoenix dactyllfera L. is closely associated with the life of the people in the Arabian Peninsula for the past 7000 years (Thomson, 1949). In the Kingdom of Saudi Arabia, the crop was attacked by the dreaded pest of palms Rhynchophorus ferrugineus Oliv. (Coleoptera: Curculionidae) during 1987 and since then the pest has spread to other date growing centres in the country (Abozuhairah et al., 1996). Red palm weevil is now reported in all the date growing countries of the middle east (Oehlschlager, 1995). Initial attempts to control the pest with insecticides in Saudi Arabia were not successful (Bokhari and Abozuhairah, 1992). Ever since Hallet et al. (1993) synthesized the male aggregation pheromone "Ferrugineol" (4-methyl-5nonanol) for R. ferrugineus and Oehlschlager (1994) demonstrated a pheromone trapping system using Ferrolure in food baited bucket traps containing insecticides, trapping the weevil using pheromone traps has become a vital component of the IPM strategy. It has been seen that weevil captures using Ferrolure in pheromone traps are female dominated with a sex ratio of 1 : 2.7 in favour of females (Anonymous, 1998). From the weevil management point of view, this is an encouraging trend. However, it is essential to know the status of the female weevils captured by pheromone traps i.e., (i) age (ii) egg laying potential and (iii) viability of the eggs laid by the trapped female weevils, as these factors have a direct relationship to the damaging potential of the pest. If trapped females are old and have already completed egg laying in the plantations, before entering the trap, then pheromone traps would not help to reduce the build up of the weevil population. In this case, pheromone traps are more likely to serve only as monitors, keeping an eye on the activity of the pest. If, on the other hand, young female weevils with potential for laying viable eggs are trapped, pheromone trapping would significantly contribute in suppressing the population build up.