Optimization of a mass-rearing system to produce codling moth, Cydia pomonella, for a Sterile Insect Release programme in South Africa

Stenekamp, Daleen (Stellenbosch : University of Stellenbosch, 2011-03)

Thesis (PhD (Conservation Ecology and Entomology))--University of Stellenbosch, 2011.

Thesis

ENGLISH ABSTRACT: Codling moth, Cydia pomonella, is a worldwide pest and of major economic importance to the South African pome fruit industry. Sterile insect release is applied as a component of area-wide integrated pest management and includes the mass-rearing, sterilization and the release of the sterile insects. For sterile insect release, the improvements of rearing methods in terms of the quality of the diet ingredients and the economical aspect of the rearing method are examined. The effect of genetically modified maize meal, containing the Bacillus thuringiensis gene, in an artificial medium for codling moth rearing, is determined. The use of even a small amount of Bacillus thuringiensis resulted in larval mortality and prolonged development. These results are detrimental to a mass-rearing facility and must be considered by any rearing facility that uses genetically modified maize meal if the insect is sensitive to the gene. An alternative to maize meal in the artificial medium was tested and whole wheat flour was considered to be a suitable replacement. Agar agar is an expensive gelling agent used in the artificial medium. An alternative for agar agar (Kelcogel, Elastigel and carrageenen) is tested and the biological effect on codling moth is determined. Factors such as mortality, pupal and moth weight, longevity, fecundity and development time were used as quality parameters. Results showed that Elastigel was a suitable replacement for agar agar, with bigger pupae and moths, higher fecundity and increased longevity. The economical advantage of the replacement is a 40.91% reduction of the diet cost. The other gelling agents tested also gave acceptable results and can be considered if shortages of agar agar or Elastigel occur. A new method of mass-rearing codling moth larvae in a closed rearing system using large trays placed in a ventilated box is designed. This method is more cost and space effective as a smaller area is needed to rear a large number of moths. The risk of diet contamination is less because of the closed environment and more economical and effective air handling. This is the first report of its kind to describe the mass-rearing of codling moth in a closed environment and the risks involved in using genetically modified maize meal in an artificial diet for the codling moth. These results should be incorporated into existing mass-rearing facilities or taking into consideration when designing new mass-rearing facilities.

AFRIKAANSE OPSOMMING: Die kodlingmot, Cydia pomonella, is van ekonomiese belang vir die Suid-Afrikaanse kernvrugte bedryf. Die steriele insek tegniek word gebruik as ‘n komponent in area-wye geïntegreerde plaagbeheer en sluit in die massa-aanteel, sterilisering en vrylaat van steriele insekte. Vir die steriele insek tegniek is die verbetering van die massa-aanteel van die kodlingmot in terme van kwaliteit van die dieet en die ekonomiese aspek van die aanteel metode ondersoek. Die effek van genetiese gemanipuleerde mieliemeel wat die Bacillus thuringiensis geen bevat, in ‘n kunsmatige voedselmedium vir die aanteel van kodlingmot, is bepaal. Daar is gevind dat die gebruik van selfs ‘n klein persentasie Bacillus thuringiensis in die mieliemeel, mortaliteit en ‘n verlengde lewenssiklus in kodlingmot veroorsaak. Die gevolge is nadelig vir ‘n massa-aanteel fasiliteit en behoort in ag geneem te word vir enige insek wat op ‘n kunsmatige medium, wat mieliemeel bevat, geteel word, mits die insek sensitief is vir Bacillus thuringiensis. ‘n Alternatiewe bestanddeel vir mieliemeel, volkoringmeel, word aanbeveel. Agar agar is ‘n duur verdikkingsagent wat in kunsmatige mediums gebruik word. ‘n Alternatief vir agar agar (Kelcogel, Elastigel en carrageenen) is getoets en die biologiese effek op die kodlingmot is bepaal. Faktore soos mortaliteit, papie en mot gewig, langlewendheid, vrugbaarheid en lengte van lewenssiklus was gebruik as kwaliteit parameters. Resultate het getoon dat Elastigel ‘n geskikte plaasvevanger is van agar agar, met groter papies en motte, groter vrugbaarheid en langlewendheid. Die ekonomiese gevolg van die plaasvervanger, is ‘n vermindering van 40.91% van die dieetkoste. Die ander verdikkingagente wat is getoets is, het aanvaarbare resultate gelewer wat noodsaaklik is indien daar ‘n tekort van Elastigel of agar agar ontwikkel. ‘n Nuwe metode van massa-aanteel van kodlingmot larwes is bepaal. Die metode behels ‘n geslote sisteem, waar groter aanteel bakke in ‘n geslote, geventileerde boks geplaas word. Die metode is koste en spasie effektief en ‘n kleiner area word benodig om ‘n groter aantal motte te lewer. Die risiko van kontaminasie van die dieet word verminder as gevolg van die geslote sisteem wat gebruik word en meer ekonomiese en effektiewe lugversorging word gebruik. Hierdie is die eerste verslag van sy soort wat die massa-aanteel van kodlingmot in ‘n geslote sisteem beskryf en wat die risiko aandui van geneties gemanipuleerde mieliemeel in ‘n kunsmatige medium vir die kodlingmot. Hierdie resultate behoort in ag geneem te word vir reeds bestaande massa-aanteel fasiliteite of met die ontwerp van nuwe massa-aanteel fasiliteite.

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