Relationship between Fruit Flies and the Bacterium Xantomonas citri pv. mangiferaeindicae: Two Major Constraints on Mango Production in West Africa

Abstract

Aims: Fruit flies and the bacterium Xanthomonas citri pv. mangiferaeindicae are major constraints on mango production in West Africa. This study aimed to shed light on the relationship between these two pests to improve methods for their control. Study Design: It was carried out from early June to mid-July 2018 in the field and in the laboratory. The laboratory tests were performed at the Farako-Bâ research station located in Bobo-Dioulasso. Methodology: Mangoes with fruit fly stings and/or bacterial canker symptoms were collected from four mango orchards to analyse the coinfection of mangoes by fruit flies and the bacterium X. citri pv. mangiferaeindicae. Fruit flies were captured using food attractants (torula yeast and M3 bait station) to analyze their role in the dissemination of the bacterium. Tests were carried out to isolate the bacteria from the fruit fly samples, nutrient broth and torula solution using YPGA medium. The mango leaves were then infiltrated with the isolated strains to observe typical symptoms caused by the bacteria. Results: Nine species of fruit flies from three genera (Bactrocera, Ceratitis and Dacus) were captured in mango orchards with food attractants. Among these species, Bactrocera dorsalis, Ceratitis cosyra and Ceratitis silvestrii emerged from mangoes infected with X. citri pv. mangiferaeindicae. On average, 49.66% to 91.66% of the mangoes infected with this bacterium were also attacked by fruit flies, depending on mango variety and symptom type. The severity of the attacks ranged from 42.50 to 210.21 pupae/kg infested mango (F value = 8.7; Pr (˃F) = .006). The pupae survived with a hatching rate of 68.21% to 74.98% (F value = 0.49; Pr (˃F) = .69). Coinfection of mangoes with fruit flies and the bacterium X. citri pv. mangiferaeindicae was therefore established. The bacterium X. citri pv. mangiferaeindicae was isolated from fruit flies captured manually. Conclusion: Fruit flies can thus be considered passive vectors of the bacterium X. citri pv. mangiferaeindicae. More in-depth studies are needed to elucidate this situation.