Characterizing the spread of banana bunchy top disease at high-altitude banana production zones in South-Kivu, Democratic Republic of Congo

Abstract

Abstract

Introduction Banana bunchy top disease (BBTD) is a major threat to Musa spp . production, and widespread in lowland banana producing regions of the Democratic Republic of Congo. Historically, low-to-mid altitude zones have been most vulnerable because temperatures favor aphid-mediated virus transmission. Recent informal reports from national research and extension services suggested an upward expansion of BBTD into the high-altitude cultivation regions of South-Kivu Province, dominated by East African Highland banana cultivars. Methods Extensive ground-based surveys were carried out in the South-Kivu territories of Kalehe, Kabare, Walungu and Idjwi, accompanied by farmer interviews. In total, 829 farms participated, comprising 464 BBTD‑affected farms and 365 disease‑free farms. Results and discussion This study confirmed BBTD was effectively established at altitudes of 1450–1780 m a.s.l., with sporadic occurrences up to 2120 m in Kabare. Aphid vectors, including winged individuals, were present throughout the altitude range 957–1874 m.a.s.l. Statistical analyses revealed a strong positive correlation between BBTD incidence and aphid presence, morph type, and maximum aphid score per farm. Notably, disease prevalence increased sharply with higher aphid scores, and even low densities of winged aphids were sufficient to drive widespread transmission. Movement of infected planting material remained a primary dissemination pathway, with minimal behavioral changes in sourcing of planting material reported in BBTD affected areas. Finally, a lack of disease management or incorrect implementation was identified. Counter-intuitively, uprooting infected mats was associated with heightened disease spread, likely due to mechanical disturbance that liberates viruliferous winged aphids or improper disposal of infected debris. Immediate, targeted extension support and refined integrated pest-management strategies are essential to mitigate BBTD impact on highland banana cultivation and safeguard food security for African small-holder farmers.