Seasonal and nocturnal activities of the rhinoceros borer (Coleoptera: Scarabaeidae) in the north Saharan oases ecosystems

Abstract

The rhinoceros borer Oryctes agamemnon Burmeister (Coleoptera: Scarabaeidae) is a date palm insect pest that causes damage to trunk and roots of palm trees in several countries, including Tunisia, the United Arab Emirates (UAE), Oman, and Saudi Arabia. The aim of this study was to monitor the seasonal and nocturnal activities of this beetle. Experiments were performed on a date palm of Rjim Maatoug during a 6-yr period (2004-2007, 2009-2010). Field survey using light traps shows that O. agamemnon is a univoltine, with a single population peak. Adults appear in the field around late May-early June and the population continued to build until maximum numbers are reached between the end of July and the beginning of August in the same year. No adults were found after first 10 d of November. This peak was characterized by female dominance in number. The monitoring of nocturnal activity showed that it starts its activities roughly 40 min after the sundown and continues until approximately 1 h before sunrise. The highest number of trapped beetles was remarked in the two first hours of flight activity, with a dominance of female in the first hour and a dominance of male in the second hour. We remarked that the sex ratio (female:male) of the cumulated number of trapped adults in the different years and nights of survey was in favor of females.

Keywords: Oryctes agamemnon; date palm; flight pattern; peak; sex ratio.

Fig. 1.

The geographic location of study area.

Fig. 2.

The light trap. The trap was designed and manufactured by ourselves with the help of private society specialized in solar energy. The trap is made up of an overcome support of a square funnel divided in four parts. The funnel itself is surmounted by a wooden carpentry which vertically supports four Plexiglas plates to facilitate fallen off insects in the funnel then they will be guided to the buckets of recuperation by means of plastic tube. All of these are supported with a framework of iron. This trap is equipped with a solar plate, a system which transforms solar energy into D.C. current, a battery to store the current, and a system which ensures the automatic starting of the light 10 min after sunset. A neon lamp with a white light color was used.

Fig. 3.

Seasonal activity of O. agamemnon . (a)Year 2004; (b) Year 2005; (c) Year 2006; (d) Year 2007; (e) Year 2009; (f) Year 2010.

Fig. 4.

Nocturnal activity of O. agamemnon .