African Crop Science Journal

Incidence moleculaire et distribution des virus associes a la Mosaique Africaine du Manioc au Sud-Kivu en Republique Democratique du Congo

J.-C. Bulonza — 2024-10-11

La maladie de la mosaïque du manioc (CMD) est une maladie redoutable des systèmes de production de manioc (Manihot esculenta Crantz) en Afrique subsaharienne. L’objectif de cette étude était d’établir les virus associés au CMD et leur distribution spatio-temporelle dans la province du Sud-Kivu en République démocratique du Congo. Au total, 590 échantillons de feuilles de manioc ont été collectés entre novembre 2020 et Mars 2022 et analysés au laboratoire à l’aide de méthodes moléculaires. Les résultats ont montré que diverses souches virales (African Cassava Mosaic Virus (ACMV), East African Cassava Mosaic Virus (EACMV), ACMV+EACMV-UG, EACMCV et souches non spécifiées) étaient largement répandues dans le Sud-Kivu. La souche EACMV-UG était répandue dans tous les territoires de la province du Sud-Kivu, tandis que la souche camerounaise (EACMCV) n’a été trouvée que dans le territoire de Kalehe (2%). Il y avait une infection mixte (ACMV+EACMV-UG), bien qu’à des niveaux faibles, passant de 2,3 % en 2020 à 3 % en 2022. Tous les territoires étudiés présentaient une grande diversité de virus, à l’exception de celui d’Uvira, qui n’avait que l’EACMV-UG. Les virus ACMV étaient les plus abondants, suivis par l’EACMV-UG, dans la région étudiée. Une forte augmentation de la diversité virale s’est produite en 2020 et 2022, avec des taux passant de 33,07 à 57,5%.

Diversité et abondance de la faune d’insectes de la laitue dans le Centre-Ouest de la Côte d’Ivoire

S. Diabate — 2024-10-11

La laitue, Lactuca sativa (Asteraceae), est un légume-feuille essentiel à la santé humaine, notamment dans les zones urbaines et périurbaines. Cependant, sa production est limitée par divers facteurs, dont l’impact des insectes. Cette étude vise à documenter la diversité et l’abondance de l’entomofaune associée à la culture de la laitue en Côte d’Ivoire. Elle a été réalisée en octobre 2023, pendant la saison des pluies, à Daloa, en utilisant des pièges jaunes et des filets fauchoirs. Au total, 980 insectes ont été capturés, répartis en 63 genres, 52 familles et 9 ordres. Les Diptères ont été les plus abondants (46 %), suivis par les Chrysomelidae (27 %), dominés par Cerotoma sp. avec 264 individus. Les défoliateurs, principalement de la famille des Chrysomelidae, ont été les nombreux dans les cultures. Les insectes bénéfiques des ordres des Hyménoptères, Coléoptères, Diptères et Odonates ont été moins représentés.
Les indices de diversité de Shannon (H’ = 1,47) et d’équitabilité (E = 0,51) ont été plus élevés pour les Diptères, tandis que les Dermaptères ont présenté l’indice de diversité le plus bas (H’= 0,03). L’indice de Simpson, bien que similaire pour tous les ordres, a été légèrement inférieur pour les Coléoptères (0,92). Cette étude offre un inventaire préliminaire des insectes associés à la culture de la laitue, fournissant une base pour de futures recherches.

Efficacy of isolates of an entomopathogenic fungus on coffee berry borer

E.J.B. Ohoueu — 2024-10-11

The coffee berry borer (Hypothenemus hampei F.; Coleoptera: Scolytidae) is an important pest of coffee in sub-Saharan Africa (SSA), which causes enormous damage to the crop and yet is difficult to control. The objective of this study was to evaluate the efficacy of Beauveria bassiana, an entomopathogenic fungi, on H. hampei F. pest under laboratory conditions. Isolates of B. bassiana were isolated using the suspension-dilution method on Beauveria Selective Medium (MSB), from Daloa (Cote d’Ivoire) soil sample. Five isolates of B. bassiana, namely TE3.211, TE3.222, TE7.311, G.233 and G.232, were tested on coffee berry borer, through two inoculation methods (active and passive). The isolation results showed that 65.51% mortality rates caused by B. bassiana varied from 48.48 to 99.66%. Isolate TE7.311 caused a mortality rate of 96.66% for active inoculation of bark beetles and 70% for passive inoculation of cherries. Isolate TE3.211 by active inoculation of bark beetles and isolate G232 by active inoculation of cherries generated mortality rates of 98.33 and 99.66%, respectively. The pathogenicity tests carried out on the bark beetle presented LT50s, which varied from day 2 to day 9 for the passive method. In contrast, as for the active method, TL50 were observed from day 1 to day 2. The results of this study confirm the efficacy of B. bassiana as biological control agents against coffee berry borer.

Determinants of sesame cultivation practices in the East region of Burkina Faso

A. Siri — 2024-10-11

Sesame (Sesamum indicum L.) is an important oilseed crop, especially in West Africa, contributing to household economies. The demand for sesame has increased remarkably; against low or declining yields. The objective of this study was to identify the major determinants of sesame cultivation in the main agro-climatic zones of the eastern Sudanian region of Burkina Faso, as a strategy for intensifying its production. A survey was carried out involving 300 sesame producers, in the eastern region of Burkina Faso; using a semi-structured. Sesame cultivation was mainly influenced by low level of knowledge of sesame production; lack of improved seed varieties among producers; inadequate soil fertility management and high costs of fertilisers and improved seeds. Factors such as gender, age, education level and land area allocated to sesame cultivation, hitherto believed to be important in sesame production, had no statistically measurable effects on crop cultivation. Allocation of mostly degraded lands to sesame production considerably affected its yield levels.

Influence of alternative plant habitats on cassava whitefly colonisation in Malawi

Y.L.B. Tembo — 2024-10-11

Cassava (Manihot esculenta Crantz) is an important food security and income generating crop in Malawi; whose productivity is constrained by the whitefly (Bemisia spp.) pest complex and associated viral diseases. Current cassava tuber yields in the country are estimated at barely 30% of the potential yield of 91 tonnes per hectare. The objective of this study was to investigate the effect of alternative whitefly host plants within habitats, on whitefly infestation in cassava fields in Malawi. A field study was conducted at Lilongwe and Nkhata Bay in Malawi, in 2017. Treatments included (i) target cassava (<2 months old, and old cassava (8 - 13 months after planting); (ii) natural vegetation; (iii) pumpkin; (iv) sweet potato; (v) beans; (vi) groundnuts; (vii) Irish potato; (viii) soybean; (ix) tobacco and (xi) tomato. Clean sentinel cassava plants were placed in each habitat (three pots per habitat), at the beginning of the growing season. They were collected after four weeks to assess the relative colonisation rates of whitefly, by determining the number of nymphs. Plants placed in the cassava habitats presented the greatest number of nymphs (39.3); followed by natural vegetation (17.8) and old cassava (14.1); compared to other habitats. There were no significant differences (P>0.05) in the amount of parasitism of nymphs between habitats. This study suggests that in diverse landscapes alternative habitats can substantially influence whitefly population dynamics in cassava fields.

Status of major potato diseases and farmer perceptions in Rwanda

A. Nduwayezu — 2024-10-11

Potato (Solanum tuberosum L.) is an important food and cash crop in most sub-Saharan (SSA) countries. Despite its popularity and surging demand, particularly among urban dwellers, potato production is generally low and decreasing in SSA, owing in part to various devastating diseases. This study aimed at assessing the intensity and distribution of major potato diseases on farms in major potato growing regions in Rwanda. A total of 120 samples of tubers and symptomatic leaves were collected from three districts, located at different altitudes, namely Kayonza (1443 - 1672 m.a.s.l), Nyamagabe (1824 - 2193 m.a.s.l) and Nyabihu (2209- 2696 m.a.s.l). The samples were used to identify and assess prevalence of diseases. Data on perceptions were collected on 148 potato farmers from the same districts, using a semi-structured questionnaire. Bacterial wilt was the most potato farmers damaging disease in the low and medium elevations, estimated at > 50% of the responders. On the other hand, late blight and viruses were the most prevalent in high elevation areas, estimated at 42 and 44% of respondents, respectively. The severity and incidence of viruses (PVS, PVX and PVY) and bacterial wilt were the most severe at the lowest elevation; but lowest at the highest elevation. Potato viruses, especially PVS, PVX and PVY; and bacterial wilt and late blight were confirmed to be the major potato diseases in Rwanda.

Factors influencing farmers’ choice of potato varieties to grow in south-western Uganda

H.D. Ssebbanja — 2024-10-11

The demand for potato (Solanum tuberosum L.) and its products is rapidly expanding in sub-Saharan Africa (SSA), owing to the unequivocal rise in human population largely through urbanisation. This study aimed at investigating the extent to which varietal and seed-system-based attributes influence the farmers’ choice of potato varieties to grow in Uganda. Data were collected from 147 purposely, potato-growing households in south-western Uganda. Varietal attributes, such as resistance to bacterial wilt, thick tuber skin texture, high dry matter content, and yield, significantly influenced the farmers’ choice of potato varieties. Thick tuber skin texture influenced varietal change positively, by 18% points. For the seed system-based attributes, distance to the seed sources, and long-term cultivation of a variety, negatively influenced potato varietal choices by 1.4 and 1.2%, respectively. It is concluded that varietal and seed system-based attributes influence potato varietal choice in south-western Uganda; although for farmers to change from one variety to another, the distance to seed sources should be minimal.