Host status of fruit flies (Diptera: Tephritidae) on French beans in Kenya

Abstract

Production of French bean (Phaseolus vulgaris L.) as a vegetable is important as a source of livelihood and income generation to smallholder farmers. However, production of this crop has not been optimal due to various constraints. Among the most important ones is pest and diseases. In Kenya, major pests reported in French beans include the western flower thrips (WFT) (Frankliniella occidentalis), Bean fly (Ophiomyia phaseoli) aphids (Aphis fabae), red spider mites (Tetranychus spp.), the African bollworm (Helicoverpa armigera), the legume pod borer (Maruca vitrata) and white flies (Bemisia tabaci). Although Tephritidae flies are major pests of fruits and vegetables in Africa, Kenya included, they are no reports to indicate that they attack French beans. However, a previous pest risk analysis report indicates that the crop is host to some species such as Dacus ciliatus and Bactrocera cucurbitaceae. In an effort to secure the international market, we conducted a study to assess French beans from Kenya to establish whether they are indeed hosts to fruit flies or not. The study was conducted in Machakos, Meru, Murang’a, Laikipia and Nyeri regions in the year 2020. In each of the study regions, sampling of pods was carried out in private farms that were planting French beans for export. A total of 2375 samples were collected from various locations in the field and from exit point for analysis. Results showed that, none of the developmental stages of fruit flies (Tephritidae) was present in any of the sampled French beans pods (Field and exit point samples). However, bean seed fly (Delia platura), bean fly (Ophiomyia phaseoli) and one beetle was recorded in some of the samples. From our study we conclude that French beans is not a host to Tephritidae fruit flies. However, we recommend host preference tests in the laboratory and greenhouse to establish the oviposition potential of the fruit flies to French beans.