Response of fruit fly populations to new management tools in mango orchards in Tien Giang Province, Viet Nam

Abstract

Mango is one of the most important tropical fruit in Viet Nam and has great potential for export. However, the presence of fruit fly (Tephritidae: Diptera) constitutes a major barrier to fruit production and access to world markets. Fruit flies are regarded as serious pests that cause significant economic losses to mango production in Viet Nam. In recent years, toxic protein baiting and fruit bagging have been adopted as new tools to control fruit flies, especially in commercial plantings. The aims of this research are to: 1) determine the effect of area-wide SOFRI Protein® baiting and fruit bagging in reducing the abundance of fruit fly in mango orchards, 2) compare the diversity of the ground-dwelling invertebrates between SOFRI Protein® treatment and non-treatment sites in mango orchards and 3) measure the developmental times and survival of the Oriental fruit fly, Bactrocera dorsalis at three different temperatures. A sixmonth survey using methyl eugenol traps detected an inventory of five fruit fly species which was dominated by B. dorsalis and B. correcta. Among them, B. osbeckiae was identified for the first time in mango orchards in Viet Nam. Whereas fruit fly abundance and diversity were not influenced by environmental variables during the investigation period, the overall mean captures per trap of males of B. dorsalis and B. correcta in SOFRI Protein® treated site were nearly four times and two times, respectively, lower than those in non-treated sites, thus indicating that SOFRI Protein® is effective in suppressing fruit fly populations in mango orchards. SOFRI Protein® was found to reduce the incidence of fruit infestation from fruit flies from 11.2% in non-treatment sites to 2.4% in that with SOFRI Protein® treatment, while fruit bagging provided a complete protection from fruit fly damage for mango. The ground-dwelling communities collected from pitfall traps in mango orchards in Tien Giang consisted of 14 taxonomic orders with 47 taxa. The composition and abundance of the soil invertebrate communities presented no measurable impact from SOFRI Protein® sprays, although this study would have only detected relatively large differences. Laboratory rearing of B. dorsalis indicated that the duration times for development for all life stages of this fruit fly shortened with increasing temperature. These differences were cumulative so that the total life cycles of B. dorsalis maintained at constant temperatures of 20, 24 and 28oC lasted 69.5 days, 34 days and 23.1 days, respectively. The results of this research provide further understanding of fruit fly populations in Viet Nam. For New Zealand, the research will have important implications on future decision-making processes regarding the mitigation measures required for mango imported from Viet Nam.