Laboratory-Rearing Techniques for Tephritid fruit flies
in Pacific Islands Countries and Territories

Introduction

A major objective of the FAO/AusAID/UNDP/SPC Regional Fruit Fly Projects in the Pacific was to undertake biological studies on the economically important multi-host species of fruit flies (Diptera: Tephritidae), particularly research on host status testing and quarantine treatments for locally produced fruits and vegetables. For these studies, a prerequisite was the supply of good quality fruit flies of specific life stages.

Regionally, over the past ten years, laboratory colonies of 20 fruit fly species have been established (see Table). One or more of these species have been maintained in each of ten Pacific Island Countries and Territories (PICTs). The emphasis, while maintaining these colonies, was on low cost, simplicity and the use of local materials wherever possible. The basis of this has been the development of artificial larval diets for which the major ingredient has been locally available fruits. The pawpaw diet is the standard diet and is used in most countries for rearing species. The diet is particularly suitable for post-harvest treatment studies when larvae of known age are required.

Table: Fruit fly species kept in colonies in PICTs. 
A = colonies still maintained / B = colonies not maintained anymore

 

Fruit fly rearing room in Bubia, Papua New Guinea (Photo: L. Leblanc)

 

Laboratory rearing techniques are based on the development of artificial diets for larvae, consisting predominately of the pulp of locally available fruits including pawpaw, breadfruit and banana. The pawpaw diet is the standard diet and is used in most countries. Diet ingredients are standard proportions of fruit pulp, hydrolysed protein and a bacterial and fungal inhibitor. The diet is particularly suitable for post-harvest treatment studies when larvae of known age are required. Another major development in the laboratory rearing system is the use of pure strains of Enterobacteriaceae bacterial cultures as important adult-feeding supplements. These bacterial cultures are dissected out of the crop of wild female flies, isolated by sub-culturing, and identified before being supplied to adult flies, as cultures on peptone-yeast extract agar plates. Some species are egged using thin, plastic receptacles perforated with 1mm oviposition holes, with fruit juice or larval diet smeared internally as an oviposition stimulant. For other species, domes of fruit with the pulp removed, leaving a thin skin punctured with a needle, are used for egging. Laboratory rearing techniques have been standardised for all of the PICTs. Quality control monitoring is based on acceptable ranges in per cent egg hatch, pupal weight and pupal mortality. Colonies are rejuvenated every 6 to 12 months by crossing wild males with laboratory-reared females and vice versa. The standard rearing techniques, equipment and ingredients used in collecting, establishment, maintenance and quality control of these fruit fly species are detailed in the following pages.

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 Page updated on: 17 October, 2002