Assessment of the entomopathogenic fungus Beauveria bassiana Saudi Arabian isolate (B -SA3) against the developemental stages of the red palm weevil, Rhynochophorus ferrungineus (oliv.) [electronic resource].

Includes reference.

The efficacy of the entomopathogenic fungus Beaveria bassiana Saudi Arabian islolate (B-SA3) was evalualed against the red palm weevil. Rynochophorus ferrungineus (Oliv.). The mentioned isolale was assessed on the different deveolpmental stages of the red palm weevil through toxicity tests, i.e. determination of lethal concentration and lelhal limes to kill 50% of treated insecls. The results showed that 8th instar larvae were the most tolerant lollowed by pupa to B.bassiana as their LC₅₀ values were 3.75x 10₈ and 3.78x10⁷ conidia/ml respectively. Meanwhile, 4th instar larvae were the most susceptible to infection by B.bassiana (B-SA 3), as LC₅₀ value wa. 3.25x 10⁶ conidia/ml, which proved insignificantly different to that adult weevils, i.e. 4.16x10⁶ conidia/mL futhermore, LT₅₀ values were very similar in these latter mentioned developmental stages in any considered concentration; meanwhile. LT₅₀ was much longer in 8th instar larvae than the other considered instar and/or developmental slages. The fungus B. bassiana was most virulent to eggs of the red palm weevil as none of the eggs hatched following their treatment with any the considered concentrations (ranging between 5x10⁹ to 5x10⁵ cosnidia/ml). Moreover, germination viability of harvested conidia of B.bassiana stored at -4C was insignificantly affected up to the 10th month storage period and was well above 90%. However, germination percentage of conidia then decreased to 70.27% after 16 months of storage. Also, the virulence of the stored conidia was tested after 1, 6, 12 and 16 months on adult red palm weevils, the LC values were 3.75x10, 4.66x10, 4.17x10 and 3.37x10 conidial/ml, respectively. These results show that there was a significant decrease in the virulence of the tested fungus when the duration of storage period was more than 10 months.

Summary in arabic.

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