Abstract
Red palm weevil (RPW), Rhynchophorus ferrugineus, is a polyphagous insect that caused economic damage in various palm species, particularly coconut plantation in Malaysia. Therefore, entomopathogenic fungus Metarhizium anisopliae was being introduced in attempts to control biologically the RPW. The entomopathogenicity of an indigenous (Met-Gra4) and foreign (Met-TH) strains of M. anisopliae isolated from the soil of Malaysia and Thailand, were tested against RPW adults in laboratory bioassays at 50, 70, 90% relative humidity (RH). Bioassays indicate no significance differences in efficacy between both the conidia of M. anisopliae strains against RPW adults. Met-Gra4 showed the highest efficacy at 90% RH (LT50 = 6.17 days). However, LT50 only slightly differed from Met-TH (6.33 days; 90% RH). Scanning el ectron microscopy for the treated RPWs showed that Met-Gra4 (90% RH) was densely sporulated within the abdomen, while Met-TH can be found mainly across cuticular surface of RPW.
Highlights
Dataset on the influence of relative humidity on the pathogenicity of Metarhizium anisopliae isolates from Thailand and Malaysia against red palm weevil (Rhynchophorus ferrugineus, Olivier) adult
Entomopathogenic fungus Metarhizium anisopliae was being introduced in attempts to control biologically the Red palm weevil (RPW)
The entomopathogenicity of an indigenous (Met-Gra4) and foreign (Met-TH) strains of M. anisopliae isolated from the soil of Malaysia and Thailand, were tested against RPW adults in laboratory bioassays at 50, 70, 90% relative humidity (RH)
Summary
Two selected virulent strains of M. anisopliae which isolated from the soil of Felda Tenang, Terengganu (Met-Gra4) and soil of Muang Chum, Kanchanaburi (Met-TH) were tested against the adults of RPW. The scanning electron micrograph of treated RPW at day nine post-treatment, hyphae of Met-Gra was deeply penetrated through the abdominal cuticular layer reaching the inner tissue component (Fig. 4b). Two plates for each soil samples were incubated for 5 – 7 days at room temperature, and based on the morphological appearance, the potential fungal colonies of readily sporulating M. anisopliae which characterized by green conidia, were subcultured by aseptically transferring the inoculum for streaking onto the freshly prepared PDA, plating in Petri dishes, and incubated at room temperature until mycelial growth has appeared. Mixed-sex adult RPWs were precleaned with running tap water before surface sterilized with 70% alcohol for 10 s, continued by immersing in sterile distilled water 3 times consecutively
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