Effectiveness of fruit flies management strategies with emphasis on establishment and dispersal of parasitoids in Mozambique

Abstract

Fruit flies (Diptera: Tephritidae) are among the most destructive pests affecting fruit production worldwide and in Africa especially B. dorsalis causing significant economic losses and restricting horticultural trade. In Mozambique, this species attacks a wide range of hosts, with potential yield losses reaching up to 80% in the absence of effective management. This study evaluated the effectiveness of integrated fruit fly management strategies in Mozambique, with emphasis on bait stations, male annihilation technique (MAT), host infestation levels, and biological control using parasitoids. Field experiments were conducted in Boane District using three treatments: control, M3 bait stations alone, and M3 combined with MAT. Fruit fly populations were monitored using torula-baited traps, while infestation indices were determined through fruit collection and incubation. In Cabo Delgado Province, host fruits were sampled at varying distances from parasitoid release sites to assess parasitism and dispersal. A total of 3450 fruit flies belonging to Bactrocera, Dacus, and Ceratitis were captured, with B. dorsalis being the dominant species (64–68% of total captures), followed by D. bivittatus. Fruit fly density of B. dorsalis significantly decreased from 8.68 flies/trap/day in the control to 4.07 and 1.25 in the M3 and M3+MAT treatments, respectively, indicating strong suppression effects. Similar trends were observed for D. bivittatus. Infestation levels varied significantly among host fruits, with guava showing the highest indices, followed by tropical almond, while citrus and june plum exhibited the lowest infestation levels. Mango showed moderate infestation across parameters. Parasitoid surveys recorded D. longicaudata and P. cosyrae in Cabo Delgado, while F. arisanus was not recovered in any location. In Maputo, only P. cosyrae was detected. In Cabo Delgado province, parasitism rates varied across sampling locations, ranging from 3.16% to 10.93%. P. cosyrae was the most widely distributed parasitoid species and was detected in all sampled sites. In contrast, D. longicaudata was recorded only in selected locations, where it exhibited higher parasitism rates than P. cosyrae, particularly in Mieze (6.55%) and Komakoma (5.5%). Despite relatively high host sample numbers in some areas, parasitism levels remained low to moderate across the study sites, indicating spatial variation in parasitoid effectiveness. The maximum dispersal distance reached 74.5 km. The observed parasitism and dispersal rates of D. longicaudata suggests that future management strategies should prioritize the conservation and augmentation of parasitoids in Cabo Delgado and Maputo Provinces.