August 2002. Vanuatu Quarantine Inspection Service has been having difficulty in raising Bactrocera umbrosa in the laboratory and asked for help. Breadfruit is the only host of this fruit fly in Vanuatu and the VQIS was interested to know if anyone has been working with this fruit fly. What is the larval diet for B. umbrosa? VQIS has tried artificial diets using papaya, breadfruit and potato with no success. They were facing difficulties with getting the fruitflies to lay eggs; they had tried papaya without success.
New Caledonia mentioned that they used carrot when they reared B. umbrosa a few years’ ago.
Information was also provided by the Pacific fruit fly project:
The best reference on artificial diets for fruit flies in the Pacific is in the paper by Walker et al. (pages 145-152) entitled Laboratory-rearing Techniques for Tephritid Fruit Flies in the South Pacific. This paper was published in the ACIAR Proceedings No. 76 ??? Symposium on the Management of Fruit Flies in the Pacific, held in Nadi, Fiji Islands, 28-31 October 1996. Specific mention is made of using a mixture of dried carrot and dried potato as an artificial medium for larvae of B. umbrosa. It was suggested that a ratio of 2:1 by weight should be tried. The diet components are listed on page 149.
If you decide to use fresh carrot or potato, it is imperative to source the carrots and potatoes from areas where soil insecticides have not been used. It was said that when carrots imported into Fiji Islands were used in the 1990s, the diet resulted in 100% mortality of eggs or first instars, due to lindane contamination.
Breadfruit pulp can be added to the carrot/potato diet or breadfruit pulp substituted for potato. Frozen pulped breadfruit can be stockpiled when the fruit is in season.
With respect to egging of B. umbrosa, artificial egging devices should be tried. These can be made from any plastic container, such as used yoghurt containers, disposable cups or specimen tubes. Drill holes in the sides and bottom of the containers and smooth the inner and outer surfaces after making holes with fine emery or sand paper. The holes need to at least 1mm in diameter. Smear the inside of the egging device with juice/pulp of breadfruit and place the container upturned on a petri dish, in a similar way that pawpaw domes are positioned for egging. There may be need to place a wad of moistened tissue paper or cotton wool inside the egging device so that the eggs that are laid do not dehydrate. This technique is covered on page 148 of the paper above.