Hortgro Science codling moth colony

Many control strategies have been used against codling moth, Cydia pomonella, a major pest on apples and pears, but it remains a risk if control measures are not applied effectively.  Mating disruption and chemical control is used as a standard practice, while the sterile insect technique was used as a semi-commercial option but is no longer available.  Alternative, integrated biological control options are the use of parasitic wasps and entomopathogenic nematodes (EPNs) but these are still under development.

A new project focusing on the use of entomopathogenic fungi (EPF) for the control of the codling moth started in 2015 (PhD study for D.Odendaal).  A continuous supply of codling moth larvae is needed for this project to be viable.  Another project that was funded for and needed codling moth adults was: “Determining the quality of mass-reared male codling moth by assessing flight performance under laboratory, semi-field and field conditions” (2014-2015).  This was for an MSc Agric student (A. Visser).  A further need for codling moth eggs was for the rearing of the Trichogramma wasp, an egg parasitoid.  Therefore, the objective of maintaining a small-scale codling moth colony was strictly to allow for research and new technology to be developed.  Based on these studies, the success of the research depends on the continuous availability of codling moth material.  As codling moth is the primary pome fruit pest, maintaining a colony will allow for integrated pest management research to be applied in orchards.

From the outset the primary task and reason for funding was maintaining codling moth.  However, due to external pressure and the inability of students to rear their own insects resulted in an upgrade from a small, single species to a multi-species rearing system.  As the year progressed, more opportunities evolved and the question was posed to rear Mediterranean fruit fly, Ceratitis capitata, for a PhD study (W. Pieterse) and false codling moth, Thaumatotibia leucotreta, for two MSc studies (A. Visser & J. von Diest).  False codling moth larvae were also needed for the use of CATTS and Vapormate® trials (Dr S. Johnson).  Finally, we were asked to maintain a mealworm colony, Tenebrio molitor, for nematode production (Dr A. Malan).

Codling moth and false codling moth were reared on an agar and carrageenan based diet.  The mealworms were reared on bran and the fruit fly on various fruit and later on an artificial diet containing mostly bran and torula yeast.  The Trichogramma wasp was supplied with codling moth eggs for rearing purposes.  Each insect species had specific environmental requirements.

An average of 22 500 codling moths, 300-400 false codling moths, 100-300 Mediterranean fruit flies were reared weekly on fruit and between 4 000 – 6 000 on an artificial medium.

A medium-scale rearing system was successfully implemented and the insects adapted well to the new environment.  Not only was there an increasing demand for rearing and maintaining of a variety of insects, but the codling moth population was adequate to supply the students with material.  The false codling moth colony, however, was more difficult to rear.  The fruit flies were reared on various fruit which affected the production numbers of the colony.  An artificial diet was more suitable for the fruit flies to ensure a stable colony.