Biotic factors (including insect pests) constrain field-grown tomato production in Senegal. However, little information is available on the identity and life system of key pests. The objectives of this study were to: (i) update key pest records of field-grown tomato in the central vegetable-producing area along the northern coast of Senegal, known as the Niayes area; (ii) map their spatial and temporal incidence and (iii) understand insecticide use by growers to control the pests. A total of 98 tomato fields distributed in three zones along a north–south transect in the Niayes area were monitored over four crop cycles from 2012 to 2014. As expected, the tomato fruitworm Helicoverpa armigera Hübner (Lepidoptera: Noctuidae) was the most destructive pest with an occurrence of 92% in sampled fields (90/98) and up to 38% damaged fruits in one field at the time of sampling. The proportion of damaged fruits did not differ among zones, but was significantly higher in the early dry season compared to the late dry season. The invasive tomato leafminer Tuta absoluta Meyrick (Lepidoptera: Gelechiidae) was detected in 53% of sampled fields (52/98), mainly in the south of the Niayes area in the late dry season. Because of their ability to adapt to unstable environment and insecticides, this insect pest assemblage is a new challenge that farmers have to deal with while decreasing their use of broad-spectrum insecticides.

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Nous exprimons nos sincères gratitudes à l'AIRD (PEERS-BIOBIO) et au programme de production agricole en Afrique de l'Ouest (PPAAO/WAAPP) pour avoir soutenu financièrement cette étude. RESUME La lutte biologique contre les ravageurs nécessite une connaissance de la dynamique des ennemis naturels. Cette étude a pour objectifs d'étudier la distribution spatio-temporelle des espèces de parasitoïdes de H. armigera dans la zone des Niayes et d'évaluer l'impact de la phénologie de la tomate et du stade larvaire sur ces parasitoïdes. Environ 1965 larves ont été collectées dans 62 parcelles de tomate dans la zone des Niayes entre 2012 et 2014. La période de culture influe sur le parasitisme dû à Apanteles SP. Les attaques du parasitoïde sont moins élevées en première partie de saison sèche, sur le premier cycle de culture suivant immédiatement la fin de la saison des pluies (0,5%) qu'en deuxième partie de saison sèche (5,1%). En fonction de la zone, le parasitisme dû à M. laphygmarum et à Apanteles SP. Est plus important dans les zones Centre et Sud que dans la zone Nord. Le stade phénologique n'influe pas sur le parasitisme de H. armigera. Les premiers stades larvaires (L1, L2, L3 et L4) sont plus parasités que les derniers stades (L5 et L6). Ces résultats contribuent à mieux comprendre le potentiel régulateur des parasitoïdes de H. armigera et leurs importances dans des stratégies de gestion intégrée.

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In Senegal, vegetable production is an important area within the agricultural sector and contributes to improve the local diet. Damage caused by aphids in particular puts heavy pressure on vegetables production. Crop associations play an important role in controlling insect pests in some countries. The aims of this study include investigations into the diversity of aphid and parasitoid populations, and an evaluation of the effects of crop associations between cabbage and pak choï. The experimental design used is a randomized block with four treatments and two controls, that is cabbage and pak choï , and two crop associations, that is pak choï between cabbage rows, and pak choï around cabbage beds. Two aphid species, Myzus persicae, and Lipaphis pseudobrassicae are identified. The Braconidae Diaeretiella rapae (Mac Intosh) (Hymenoptera: Braconidae) is the only parasitoid met during the study. Myzus persicae (Sulzer) is more abundant than Lipaphis pseudobrassicae (Davis). Myzus persicae and L. pseudobrassicae were not controlled by the cabbage / pak choï associations. Aphids populations decreased during the heading phase of the cabbage. This preliminary study contributes to a better understanding of the potential use of crop associations to manage cabbage aphid populations in Senegal.