Pathogenicity of indigenous entomopathogenic nematodes from Benin against mango fruit fly (Bactrocera dorsalis) under laboratory conditions

Bactrocera dorsalis fruit fly is the economically most significant tephritid pest species on Mango, Mangifera indica L., in Benin, and entomopathogenic nematodes (EPNs) represent good candidates for its control in the soil. In this study, the susceptibility of larvae and pupae of B. dorsalis to 12 EPN isolates originating from Benin was investigated. The effect of nematode concentrations (20, 50, 100, 200 and 300 Infective Juveniles (IJs)/B. dorsalis larva) and of different substrate moisture content (10, 15, 20, 25 and 30% v/w) on B. dorsalis mortality at the larval stage was studied. Also, the reproduction potential inside B. dorsalis larvae was assessed. Our results revealed that the susceptibility of B. dorsalis larvae was significantly different among the 12 tested nematode isolates with H. taysearae isolate Azohoue2 causing the greatest insect mortality (96.09 +/- 1.44%). The lowest insect mortality (7.03 +/- 4.43%) was recorded with Steinernema sp. strain Bembereke. Significant differences in insect mortality were recorded when EPNs were applied at varying IJs concentrations. A concentration of 100 nematodes of either H. taysearae Azohoue2 or H. taysearae Hessa1 per B. dorsalis larva was enough to kill at least 90% of B. dorsalis larvae. Larvae were less susceptible to nematodes at higher moisture content (25% and 30%). In addition, pupae were less susceptible to nematodes than larvae. Furthermore, the tested nematode isolates were able to reproduce inside B. dorsalis third instar larva with the Heterorhabditis isolates giving the greatest multiplication rate (59577.2 IJs +/- 14307.41).