Entomopathogenic nematodes (Rhabditida: Steinernematidae and Heterorhabditidae) for the control of codling moth, Cydia pomonella (L.) under South African conditions
Date
2008-12
Authors
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Publisher
Stellenbosch : Stellenbosch University
Abstract
The codling moth, Cydia pomonella (L.), is a key pest in pome fruit orchards in South Africa. In the
past, broad spectrum insecticides were predominantly used for the local control of this moth in
orchards. Concerns over human safety, environmental impact, widespread dispersal of resistant
populations of codling moth and sustainability of synthetic pesticide use have necessitated the
development and use of alternative pest management technologies, products and programmes, such
as the use of entomopathogenic nematodes (EPNs) for the control of codling moth.
Entomopathogenic nematodes belonging to either Steinernematidae or Heterorhabditidae are ideal
candidates for incorporation into the integrated pest management programme currently being
developed for pome fruit orchards throughout South Africa with the ultimate aim of producing residuefree
fruit. However, these lethal pathogens of insects are not exempted from governmental
registration requirements and have therefore not yet been commercialized in South Africa. A nontarget
survey was conducted to find suitable isolates of EPNs from local soils and to test their
effectiveness as control agents against the codling moth. Soil samples were collected from several
habitats and regions throughout South Africa and nematodes were recovered using the insect baiting
technique. All EPN isolates obtained were identified to species level using a molecular taxonomic
approach. Entomopathogenic nematodes were recovered from 20 of the 200 soil samples (10 %). Of
these, eight (40 %) yielded Steinernema spp., identified as three isolates of S. khoisanae and five
undescribed Steinernema spp. The other 12 (60 %) of the samples were positive for Heterorhabditis
spp. and included six isolates of H. bacteriophora, five H. zealandica and one H. safricana. These
isolates were then evaluated in laboratory bioassays for their potential as microbial agents of codling
moth under varying conditions. A morphometric study indicated that all natural openings (mouth, anus
and spiracles) of final instar codling moth were large enough for the infective juveniles (IJs) of all
tested EPN species to gain entry into the larvae.
Description
Thesis (MScAgric (Conservation Ecology and Entomology))--Stellenbosch University, 2008.
Keywords
Entomopathogenic nematodes, Codling moth, Cydia pomonella, Biological control, Dissertations -- Conservation ecology and entomology, Theses -- Conservation ecology and entomology