Selection of Entomopathogenic Fungi for the Biological Control of Demotispa neivai (Coleoptera: Chrysomelidae) in Oil Palm Plantations in Colombia

Abstract

Abstract Demotispa neivai (Bondar) is an economically important pest of oil palm, Elaeis guineensis Jacq., plantations in Colombia. During our search for alternatives to conventional chemical insecticides for controlling D. neivai, we initially screened 50 isolates of various entomopathogenic fungi against adults and larvae. At a concentration of 1 × 107 conidia/ml, 28 of the isolates caused fungal-induced mortality. Isolates of Metarhizium anisopliae (Metchnikoff) Sorokin, designated CPMa1502 and CeMa9236, caused the greatest mortality in adults and larvae. These isolates were further evaluated for efficacy against natural infestations of D. neivai in oil palm fruit bunches by applying each isolate at a rate of 1 × 1013 conidia/ha. The CPMa1502 isolate caused a significantly (F = 39.22; df = 6, 8; P < 0.0001) higher larval mortality (87.7%) than that of the CeMa9236 isolate. Three concentrations (5 × 1012, 7.5 × 1012, and 1 × 1013 conidia/ha) of the CPMa1502 isolate were then compared in a field efficacy test, and no significant differences were observed among the treatments. CPMa1502 also was applied to commercial oil palm plantations in two tests at a rate of 1 × 1013 on a large plot with 23 palms and a rate of 5 × 1012 conidia/ha on a 511-palm plot. Larval mortality in these field tests was greater than 62%.