Appolinaire Adandonon

Ant cues affect the oviposition behaviour of fruit flies (Diptera: Tephritidae) in Africa

Abstract. Although most studies on fruit fly oviposition behaviour focus on horizontal interactions with competitors and cues from host plants, vertical interactions with predators are poorly documented. The present study provides direct evidence indicating that the oviposition behaviour of the two main mango fruit fly species, Ceratitis cosyra (Walker) and Bactrocera invadens Drew‐Tsurata & White, is affected by secretions of the dominant arboreal ant Oecophylla longinoda (Latreille). When offered ant‐exposed and unexposed mangoes in the absence of the ants, both fly species are reluctant to land on ant‐exposed fruits and, when having landed, often take off quickly and fail to oviposit. The number of puparia collected from unexposed mangoes is approximately eight‐fold higher than from ant‐exposed ones. The results obtained from laboratory experiments and field observations confirm that adult fruit flies are more affected through repellence by ant cues than by direct predation. The use of cues by fruit flies in predator avoidance has implications for evolutionary ecology, behavioural ecology and chemical ecology.

Density of pheromone sources of the weaver ant #Oecophylla longinoda# affects oviposition behaviour and damage by mango fruit flies (Diptera:Tephritidae)

As damage by the fruit flies Bactrocera invadens and Ceratitis cosyra is significantly reduced in mango trees with weaver ants, but we rarely observed adult flies being captured, we investigated whether Oecophylla pheromones affect fruit fly oviposition behaviour. Mangoes were collected within 1 m and 1–3 m distance from ant nests, and from ant-free trees. Using both choice and no-choice tests, fruit flies were allowed to oviposit on fruits for 72 h in the absence of ants. Flies landed significantly more and spent more time on fruit from ant-free than from ant-colonized trees. The density of ant pheromone sources significantly affected the oviposition time and the number of fruit fly pupae collected per kg fruit under greenhouse conditions. However, field data did not show any difference in damage for fruit collected within 1 m and 1–3 m distance from ant nests, suggesting that physical or visual mechanisms complement the repellencey effect of ant pheromones against fruit flies.

Preliminary inventory of parasitoids associated with fruit flies in mangoes, guavas, cashew pepper and wild fruit crops in Benin

Fruit flies are pests of great economic importance due to their quarantine pest status and losses recorded in West Africa. An inventory of parasitoids associated with fruit flies in mangoes, guavas, cashew, pepper and major wild fruit crops was carried out in northern-central Benin in 2005, 2006, and 2008. Tephritid parasitoids reared from field-collected fruits belonged to three families: Braconidae (97.2%), Eulophidae (1.6%) and Pteromalidae (1.2%). Fopius caudatus (Szépligeti) accounted for 73.8% of all the parasitoids and therefore was the most abundant and widely distributed parasitoid. The parasitism rate was 7.7%, with the highest recorded in wild fruit crop habitat. Ceratitis cosyra (Walker) (77%) was the fly host most commonly reared from fruits that produced F. caudatus. The recently introduced pest Bactrocera invadens Drew Tsuruta and White was rarely parasitized and only by Pachycrepoideusvindemmiae (Rondani) (Hymenoptera: Pteromalidae) at this time. This is the first report of the inventory of one native parasitoid species from B. invadens in Africa, especially in West Africa.

Seasonal Abundance of Mango Fruit Flies (Diptera: Tephritidae) and Ecological Implications for Their Management in Mango and Cashew Orchards in Benin (Centre & North)

ABSTRACT We report the results of a large-scale (six orchards) and long-term (5-yr) study on seasonal population fluctuations of fruit flies (Diptera Tephritidae) in mango (2005–2009) and cashew (2007–2009) orchards in the Borgou Department, Benin. During the five consecutive years of mango fruit fly monitoring, 25 tephritid species were captured including three species of Bactrocera, 11 of Ceratitis, and 11 of Dacus, which is represented by 2,138,150 specimens in mango orchards. We observed significant differences in Bactrocera dorsalis (Hendel) counts between “high” and “low” mango production years from 2005 to 2008 but not in Ceratitis cosyra (Walker) counts. The native species, C. cosyra, the most abundant species during the dry season, peaked beginning of May, while the exotic species, B. dorsalis, the most abundant species during the rainy season, peaked in June. Preliminary results underlined the role of nine species of wild hosts and seven species of cultivated ones around mango orchards that played an important role in maintaining B. dorsalis in this Sudan zone all year round. The presence of C. cosyra stretched over 9 mo. During the first 14 wk of tephritid monitoring on cashew orchards situated near mango orchards, most flies (62%) were captured in traps positioned in cashew orchards, showing the strong interest of an early fly control on cashew before the mango season. According to these results, in the Sudan zone, effective and compatible control methods as proposed by the IPM package validated by the West African Fruit Fly Initiative project against mango fruit flies are proposed for a large regional tephritid control program in same zones ofWest Africa.

First Report of Xanthomonas citri pv. mangiferaeindicae Causing Mango Bacterial Canker on Mangifera indica L. in Benin

Xanthomonas citri pv. mangiferaeindicae causing bacterial canker (or black spot) is a major mango (Mangifera indica L.) pathogen in tropical and subtropical areas (3). The bacterium infects a wide range of mango cultivars, and induces raised, angular, black leaf lesions, sometimes with a yellow chlorotic halo. Fruit symptoms first appear as small water-soaked spots on the lenticels turning into star-shaped, erumpent lesions, which exude an infectious gum, yielding tear-stain patterns. Severe infections cause severe defoliation and/or premature fruit drop. Twig cankers are potential sources of inoculum and weaken branch resistance to winds. Drastic yield losses have been reported at grove scale for susceptible cultivars (3). Mango leaves showing typical angular, black, raised leaf lesions were first observed and collected in April 2014 from trees cv. Kent in five localities of the Korhogo province of Ivory Coast (i.e., the major commercial mango-growing area in this country). Non-pigmented Xanthomonas-like colonies were isolated on KC semi-selective medium (4). Five strains (LL60-1, LL61-1, LL62-1, LL63-1, and LL64-1), one from each locality, were compared by multilocus sequence analysis (MLSA) to the type strain of X. citri and the pathotype strain of several X. citri pathovars, including pvs. anacardii and mangiferaeindicae. This assay targeted the atpD, dnaK, efp, and gyrB genes, as described previously (2). Nucleotide sequences were 100% identical to those of the pathotype strain of X. citri pv. mangiferaeindicae whatever the gene assayed, but differed from any other assayed X. citri pathovar. Leaves of mango cv. Maison Rouge from the youngest vegetative flush were infiltrated (10 inoculation sites/leaf for three replicate leaves on different plants/bacterial strain) as detailed previously (1) with the same five strains. Bacterial suspensions (~1 × 105 cfu/ml) were prepared in 10 mM Tris buffer (pH 7.2) from 16-h-old cultures on YPGA (7 g yeast, 7 g peptone, 7 g glucose, and 18 g agar/liter, pH 7.2). The negative control treatment consisted of three leaves infiltrated with sterile Tris buffer (10 sites/leaf). Plants were incubated in a growth chamber at 30 ± 1°C by day and 26 ± 1°C by night (12-h day/night cycle) at 80 ± 5% RH. All leaves inoculated with the strains from Ivory Coast showed typical symptoms of bacterial canker a week after inoculation. No lesions were recorded from the negative controls. The pathogen was recovered at high population densities (>1 × 106 cfu/lesion) from leaf lesions, typical of a compatible interaction (1) and isolated colonies were identified as the target by atpD sequencing (2). Kochs postulates have therefore been fully verified. This is the first report of the disease in Ivory Coast, a country which has been an internationally significant mango exporter (up to 15,000 tons per year) over the last two decades. A high disease incidence and severity were observed, outlining the need for implementing integrated pest management in mango groves and the production of disease-free nursery stock. This report further expands the distribution of the pathogen in West Africa after its first description from Ghana in 2011 (5) and subsequently in other neighboring countries. References: (1) N. Ah-You et al. Phytopathology 97:1568, 2007. (2) L. Bui Thi Ngoc et al. Int. J. Syst. Evol. Microbiol. 60:515, 2010. (3) L. Gagnevin and O. Pruvost. Plant Dis. 85:928, 2001. (4) O. Pruvost et al. J. Appl. Microbiol. 99:803, 2005. (5) O. Pruvost et al. Plant Dis. 95:774, 2011.

Seasonal pattern in food gathering of the weaver ant Oecophylla longinoda (Hymenoptera: Formicidae) in mango orchards in Benin

Prey capture and food scavenging activities of Oecophylla longinoda were monitored through regular weekly samplings during two consecutive years (2009–2010) in a large mango orchard of the Borgou Department of Benin, West Africa, a main mango production area located in the Sudan agro-ecological zone. In both years, interspecific competition with other ants occurred mainly during the dry season (January to March) resulting in increased captures of Formicinae, Myrmicinae and Ponerinae. More prey was caught during the rainy season (end April to end October) than during the rest of the year, with Diptera and Coleoptera prey peaking in May and June, respectively, along with the mango season. As insect prey quickly decreased during November to December weaver ants increasingly collected seeds and plant debris. A total of 241 species of insects were captured including 61 species (25.3%) associated with mango and a few with cashew, among which 48 mango pest species (78.7% of species associated with mango tree). Only five species (2.1%) of beneficial insects were captured. It is concluded that the presence of O. longinoda colonies is beneficial to perennial tree cropping systems such as mango and cashew.

The Use of Weaver Ants in the Management of Fruit Flies in Africa

Generalist predators such as the weaver ant, Oecophylla longinoda (Latreille), play an important role as biological control agents in West African orchards and, by extension, also in forest and savanna ecosystems within sub-Saharan Africa. These weaver ants are one of the most effective and efficient predators of arthropods in perennial tropical tree crops; their presence also acts as a deterrent to insect herbivores, particularly tephritid female fruit flies, due to the semiochemicals they produce. Emerging African markets for organic and sustainably-managed fruits and nuts have encouraged an interest in the use of weaver ants. Protection of tropical forests and savannas is ecologically and environmentally crucial and also essential for the protection of O. longinoda.