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

Quality control and recording procedures

Quality control of mass-reared insects is divided commonly into two categories:

1. production quality control where the parameters of rearing are addressed and which include such items as diet ingredients and environmental conditions; and

2. product quality control where the insects produced are evaluated.

Production quality control includes standardizing the use and storage of materials and ingredients, monitoring production processes, and ensuring facility and equipment maintenance. For monitoring purposes, all rearing cages are labeled with date, species and cage number, and all rearing containers with relevant information, e.g. weight of diet, number of eggs, diet type, date, and fruit fly species. Recording room temperatures and relative humidity is essential. All unusual observations should be noted along with any deviations from normal practice, e.g. diet wetness, growth on diet surface, abnormal condensation in larval diet container. These comments may help identify the source of any problems found later with the quality of flies or pupae.

In the second category, product quality control, the quality of the fruit fly rearing system can normally be assessed at the pupal stage and can be correlated to pupal size. However, pupal weight changes over time so that comparisons should be made with equal-aged pupae. Other simple tests of quality include percentage adult emergence (or percentage pupal mortality), percentage flight ability and percent survival. Records should be kept of colony progress so that any anomalies associated with rearing processes can be quickly identified and overcome. Generation number, daily egg production, per cent egg hatch, ratio of numbers of eggs to weight of diet, larval duration, and pupal recovery should all be recorded. Significant adult mortality in cages only 3-4 weeks old, or high numbers of flightless adults, are indicators that there is a problem with the laboratory colony.

Quality assurance monitoring in the Pacific Island Countries and Territories (PICTs) is based mainly on the pupal stage (weight and mortality) and egg hatch. There are variations between individual fruit fly species in any country and between the same species in different countries, but there is a range that indicates a colony is healthy. Checks on these variables are conducted continuously and recorded for future reference. Details on guides to quality control and fault-finding guidelines can be found in Walker and Hamacek (1992) and are summarized as follows:

Guide to quality control:

            Adults:     o    Check every cage daily (record any observations)
                               o    Cages must be kept reasonably clean (water containers and protein cards replaced weekly)
            Eggs:        o    Egging device must not dessicate
                               o    Eggs must always remain moist
                               o    Always wash fruit or fruit dome thoroughly
                               o    Egg hatch should be >70% and around 75-95% (test of 100 eggs on moist filter paper)
            Larvae:    o    Should not be handled or disturbed unnecessarily
                               o    Should not be handled or disturbed unnecessarily
                               o    Must be given moist substrate for pupation
                               o    Kept in container with good heat and gas exchange
            Diet:          o    Must remain moist
                               o    Must be made of regular quality good quality food
                               o    A continuous supply of all ingredients must be available
                               o    All ingredients must be mixed thoroughly (especially anti-fungal such as Nipagin)
            Pupae:     o    Keep in moist sawdust 
                               o    Weight of 100 pupae should be regular
                               o    Pupal mortality <10% (test on 100 pupae)
                               o    Pupal recovery from eggs should be >60%
                               o    Adult recovery from eggs should be 45-50%

            General:   o    Monitor temperature continuously (25-28°C)
                               o    Check water and food available for all fruit flies at all stages daily
                               o    Check ant traps daily
                               o    Wash cage covers, containers, etc in water or a sodium hypochlorite (0.1%) solution
                               o    Check good natural light, and complement with artificial light if necessary
                               o    Keep Drosophila out of culturing, as they compete for diet and transmit bacterium
                                            (Serratia sp) that is deletorious to fly cultures

Fault finding guidelines

Data recording

A standard data sheet  for recording laboratory collection data is available in PDF form. (Note that the reports are in Portable Document File (PDF) format. They may be downloaded and examined with Adobe Acrobat Reader program, which may be obtained for free by contacting: http://www.adobe.com/ ):

Laboratory Hygiene

Rearing facilities should have a high standard of hygiene to minimise the risk of bacterial contamination. Bacillus spp. and Serratia marcescens are known pathogens of fruit flies. All cage covers, frames and all containers used to hold eggs, larvae, pupae and implements should be disinfected in 0.2% sodium hypochlorite (NaClO) and then well rinsed in fresh water (preferably three times) before re-using. Benches should be regularly cleaned with water or wiped down with ethyl alcohol.

References

The text used in this guide has been essentially extracted from the following paper:

Walker, G.P., Tora Vueti, E., Hamacek, E.L., and A.J. Allwood. 1997. Laboratory-rearing techniques for Tephritid fruit flies in the South Pacific. Pp. 145-152 in: in: Allwood, A.J., Drew, R.A.I. 1997. Fruit fly management in the Pacific. ACIAR Proceedings No 76. 267pp.

Some other useful references include:

Boller, E.F., Katsoyannos, B.I., Remund, U. and Chambers, D.L 1981. Measuring, monitoring and improving the quality of mass-reared Mediterranean fruit flies, Ceratitis capitata (Wied.). 1. The RAPID quality control system for early warning. Zeitschrift fur Angewandte Entomologic, 92: 67-83.

Calkins, C.O. 1989. Quality Control. In: Robinson, A.S. and Hooper, G., ed., Fruit flies: their biology, natural enemies and control, Elsevier, Amsterdam, 3B: 153-165.

Drew, R.A.I. and Lloyd, A.C. 1989. Bacteria associated with Fruit Flies and their Host Plants. In: Robinson, A.S. and Hooper, G., ed., Fruit flies: their biology, natural enemies and control, Elsevier, Amsterdam, 3B: 129-140.

Hooper, G.H.S. 1978. Effects of larval rearing temperature on the development of the Mediterannean fruit fly, Ceratitis capitata. Entomologia Experimentalls cl Applicata, 23:222-226.

Lemontey, J.M. and Mademba-Sy, F. 1995. The Fruit Fly Research Programme in New Caledonia. Fruits, 49 (5-6): 421-427.

Leppla, N.C. 1984. Mass production of biological control organisms. In: King, E.G. and Leppla, N.C., ed., Advances and Challenges in Insect Rearing. Agric. Res. Sery., USDA, U.S. Government Printing Office, Washington, D.C., 292-294.

Leppla, N.C. 1989. Laboratory colonization of fruit flies. In: Robinson, A.S. and Hooper, G., ed., Fruit flies: their biology, natural enemies and control, Elsevier, Amsterdam, 3B: 91-104.

Tsitsipis, J.A. 1989. Nutrition. In: Robinson, A.S. and Hooper, G., ed., Fruit flies: their biology, natural enemies and control, Elsevier, Amsterdam, 3A: 103-119.

Vargas, R.I. 1989. Mass production of Tephritid Fruit Flies. In: Robinson, A.S. and Hooper, G., ed., Fruit flies: their biology, natural enemies and control, Elsevier, Amsterdam, 3B. 141-151.

Vargas, R.l., Mitchell, S., Chiou-Ling Hsu and Walsh, W.A. 1993. Evaluation of mass-rearing procedures for Bactrocera latifrons (Diptera: Tephritidae). Journal of Economic Entomology, 86, 4: 1157-1161.

Walker, G.P. and Hamacek, E.L. 1992. Laboratory Rearing of Fruit Flies. Lecture 7. Third International Training Course on Understanding and Managing Fruit Flies. FAO/AIDABIUNDPISPC/Regional Fruit Fly Project.

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 Page updated on: 17 October, 2002