Abstract

Entomopathogenic fungi are regarded as effective biocontrol agents in pest management. Different fungi isolates exhibit varying degree of pathogenicity against red palm weevil [Rhynchophorus ferrugineus (Olivier)]. The pathogenicity of four native isolate from Saudi Arabia (three Beauveria bassiana named as BbSA-1, BbSA-2, BbSA-3 and one Metarhizium anisopliae regarded as MaSA-1) and three exotic isolates from Indonesia (B. bassiana coded as BbIDN-1 and M. anisopliae named as MaIDN-1 and MaIDN-2) was evaluated against red palm weevil under laboratory conditions. The isolates were applied to eggs (1 day old), larvae (3 and 35 days old), pupae (5 days old) and adults (10 days old). The average mortality rate of eggs and hatched larvae was 100% in all of the isolates except BbSA-2 and BbIDN-1, where mortality was 93.3 and 90%, respectively. The lowest mortality rate (73.3%) was recorded for BbSA-3 against 3-days-old larvae; however, all other isolates caused >80% larval mortality. Meanwhile, 93.3% mortality of 35-day-old larvae was noted for MaSA-1 isolate. The highest pupa mortality (80%) was observed for MaSA-1, while remaining isolates caused >60% mortality. The isolates BbSA-1 and MaSA-1 caused 61 and 74.3% mortality in adults, respectively. The tested fungi isolates exhibited high virulence against all life stages of red palm weevil. Local isolates had higher pathogenicity than exotic isolates. The findings of the current study suggest that entomopathogenic fungi could be used as biological control agents for the management of red palm weevil. However, field studies are needed to reach the sound conclusions and practical applications.

Highlights

  • Red palm weevil [Rhynchophorus ferrugineus (Olivier)] is one of the notorious pests in date palm orchards around the world

  • Results show that high concentrations of fungi isolates caused higher mortality rates, as more conidia give a better chance of successful infection

  • B. bassiana and M. anisopliae isolates were tested under laboratory conditions at different concentrations (1 × 103 to 1 × 105 conidia/ml) which caused 100% larval mortality in RPW within 9 days at a high concentration [34]

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Summary

Introduction

Red palm weevil [Rhynchophorus ferrugineus (Olivier)] is one of the notorious pests in date palm orchards around the world. Entomopathogenic nematodes belonging to Steinernema and Heterorhabditis genera caused 100% mortality in larvae and adults of RPW under laboratory conditions, while larval mortality was 67% under field conditions [7]. B. bassiana and M. anisopliae caused 95% mortality in RPW adults through an auto-contamination trap under laboratory conditions [18]. Another recent study found that different B. bassiana isolates at 3×108 concentration caused 75–90% mortality after 7 days’ application when tested on third instar RPW larvae [20]. The current study evaluated the pathogenicity of several native and exotic fungi isolates against different life stages of RPW to obtain potential isolates suitable for field applications. This might be due to the difference in pathogenicity between the geographic region of the isolates and the insect host

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