Effect of entomopathogenic fungi on feeding and oviposition of oil palm pest Coelaenomenodera lameensis (Coleoptera: Chrysomelidae)

Oil palm, the main source of vegetable oil, is under attack from the leafminer Coelaenomenodera lameensis Berti et Mariau (Coleopera: Chrysomelidae). The adults of this insect feed on the leaflets, causing the palms to dry out. The aim of this study was to evaluate the effect of the entomopathogenic fungi Metarhizium anisopliae (Met 358 and Met 359) and Beauveria bassiana (Bb 11) on the feeding and oviposition activity of C. lameensis. The work was carried out under controlled infestation on an oil palm plot at the University Jean Lorougnon Guédé in Daloa. Male and female adults were collected and placed on leaflets covered with muslin sleeves. These leaflets served as a substrate for C. lameensis feeding and oviposition. Two feeding scenarios were considered. In the first case, the adults were placed on treated leaflets; in the second the entire setup (insects and leaflets) was treated. With regard to oviposition activity, pairs of C. lameensis surviving treatments with different entomopathogenic fungi were placed in sleeves. The length of the furrows dug when adults were placed on treated leaflets was reduced in males and females to 10.83 cm (Met 358) and 8.42 cm (Met 359) respectively, compared with the control which was 22.60 cm (males) and 30.65 cm (females). When both insects and leaflets were treated, furrow length was significantly reduced in males and females, with 7.46 cm (Met 359) and 0 cm (Met 359) respectively. The number of eggs laid by C. lameensis females surviving the treatments was reduced from 40 (Bb 11), 32 (Met 358) and 25 (Met 359) on day 5 to 0 for all fungi on day 40. This study demonstrates the potential of these entomopathogenic fungi as effective biocontrol agents as part of an integrated pest management strategy for sustainable oil palm cultivation.