Recaptures of feral Bactrocera dorsalis and B. umbrosa (Diptera: Tephritidae) males after feeding on methyl eugenol

Two major fruit fly pest species, Bactrocera dorsalis and B. umbrosa, are strongly attracted to methyl eugenol (ME) found in >450 plant species. They are, however, exclusive pollinators of certain daciniphilous (attracting Dacini fruit flies) Bulbophyllum orchids. A comparison between the recaptures of feral males after feeding ad libitum on 0.6 mg ME (simulating an average floral quantity of an orchid flower - Trial 1) and 480 mg in Trial 2 was investigated using the non-invasive capture-mark-release-recapture (CMRR) technique. Based on daily CMRR over a 16-day period, using a different colour enamel paint each day, percentages of B. dorsalis males recaptured in Trial 1 were significantly higher than those in Trial 2. However, for B. umbrosa, percentages of recaptures for different day-specific colours were highly variable due to low fly numbers captured/day. In Trial 1, of 756 B. dorsalis males released, 36.4% were recaptured once, 7.7 twice, 2.4 three times and 0.4 four times. While in Trial 2 of 1157 released males, 6% were recaptured once and 0.3% twice. Of 67 B. umbrosa males released, 28.4% were recaptured once and none more than once in Trial 1. Nevertheless, of 119 flies released in Trial 2, 25.2% were recaptured once and 3.3% twice. Overall, many marked males did return to a single ME-source to 'refuel' ME (a sex pheromone precursor). The results also show that a relatively high number of flies paid multi-visitations to a single 0.6 mg ME-source and indicate that the presence of natural ME-sources may impact area-wide IPM programmes.