Abstract
The red palm weevil Rhynchophorus ferrugineus is a serious pest of date palm in different regions of the Middle East. The present study was carried out to evaluate comparatively the effects of pyriproxyfen (insect growth regulator), neemazal (a plant product) and spinetoram (a bacterial product) on growth, development and adult performance of this insect pest. The early 5th instar larvae were treated with five sublethal concentrations of each compound. The most important results can be summarized as follows. Both larval duration and weight were considerably reduced by Spinetoram. Pyriproxyfen significantly reduced the larval duration only at 4000 ppm (7.2±2.97, compared to 11.7±1.6 days control insects) but Neemazal could not exhibit a remarkable effect. The strongest reducing effect on larval weight was recorded for Pyriproxyfen, since the growth inhibition% was determined as 49.10, 48.58 and 38.04, at 4000, 2000 and 1000 ppm, respectively. Pupation was inhibited by all tested insecticidal compounds and the pupal duration was significantly shortened, except at the lower three concentrations of Neemazal. Some deformations had been recorded only in adults, irrespective of the tested compound. The adult longevity was significantly shortened at the higher concentrations of each compound.
Highlights
The red palm weevil (RPW) Rhynchophorus ferrugineus Olivier is a dangerous insect pest of date palm in the Arabian Gulf region since the mid-1980s and Egypt since1992 (Saleh, 1992; Cox, 1993)
Similar results had been reported for prepupae and pupae of the same weevil by the plants products, Azadirachtin, jojoba oil, and the insect growth regulators (IGRs), Lufenuron and Diofenolan (Tanani, 2001)
The present result was in accordance to some reducing effects different extracts and compounds on the body weight in different insects, such as the Egyptian cotton leafworm Spodoptera littoralis after treatment with Neemazal (Ghoneim et al, 2000), the false stable fly Muscina stabulans after treatment with Margosan-O (Al-Dali et al, 2003) and the house fly Musca domestica after treatment with Margosan-O (Amer et al, 2004), and the desert locust Schistocerca gregaria after treatment with neemazal (Hamadah, 2009)
Summary
The red palm weevil (RPW) Rhynchophorus ferrugineus Olivier is a dangerous insect pest of date palm in the Arabian Gulf region since the mid-1980s and Egypt since1992 (Saleh, 1992; Cox, 1993). Different insecticide alternatives should be taken in consideration Some of these alternatives are insect growth regulators (IGRs), like Pyriproxyfen, plant extracts, like neem formulations, and microbial products, like Spinetoram. Spinetoram (microbial product) has been derived from soil-dwelling bacteria Saccharopolyspora spinosa and exerts its toxic action by contact or ingestion (Sparks et al, 1998) It targeting a nicotinic acetylcholine receptor as well as ɤaminobutyric acid (GABA) gated chloride channels causes insect paralysis (Watson 2001; Sparks, 2004; Sarfraz et al, 2005). The objective of the current study was to evaluate the disruptive effects of certain insecticide alternatives (pyriproxyfen, neemazal and spinetoram) on the growth, development and adult performance of Rh. ferrugineus
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