Entomopathogenic nematodes (Rhabditida: Steinernematidae and Heterorhabditidae) for the control of codling moth, Cydia pomonella (L.) under South African conditions

[摘要] The codling moth, Cydia pomonella (L.), is a key pest in pome fruit orchards in South Africa. In thepast, broad spectrum insecticides were predominantly used for the local control of this moth inorchards. Concerns over human safety, environmental impact, widespread dispersal of resistantpopulations of codling moth and sustainability of synthetic pesticide use have necessitated thedevelopment and use of alternative pest management technologies, products and programmes, suchas the use of entomopathogenic nematodes (EPNs) for the control of codling moth.Entomopathogenic nematodes belonging to either Steinernematidae or Heterorhabditidae are idealcandidates for incorporation into the integrated pest management programme currently beingdeveloped for pome fruit orchards throughout South Africa with the ultimate aim of producing residuefreefruit. However, these lethal pathogens of insects are not exempted from governmentalregistration requirements and have therefore not yet been commercialized in South Africa. A nontargetsurvey was conducted to find suitable isolates of EPNs from local soils and to test theireffectiveness as control agents against the codling moth. Soil samples were collected from severalhabitats and regions throughout South Africa and nematodes were recovered using the insect baitingtechnique. All EPN isolates obtained were identified to species level using a molecular taxonomicapproach. Entomopathogenic nematodes were recovered from 20 of the 200 soil samples (10 %). Ofthese, eight (40 %) yielded Steinernema spp., identified as three isolates of S. khoisanae and fiveundescribed Steinernema spp. The other 12 (60 %) of the samples were positive for Heterorhabditisspp. and included six isolates of H. bacteriophora, five H. zealandica and one H. safricana. Theseisolates were then evaluated in laboratory bioassays for their potential as microbial agents of codlingmoth under varying conditions. A morphometric study indicated that all natural openings (mouth, anusand spiracles) of final instar codling moth were large enough for the infective juveniles (IJs) of alltested EPN species to gain entry into the larvae.

[发布机构] Stellenbosch University