Survey of Cassava Mosaic Disease Incidence in Lagos State Peri-Urban Farms, South West Nigeria

Cassava Mosaic Disease (CMD), caused by a complex of begomoviruses transmitted by the whitefly Bemisia tabaci, remains one of the most devastating constraints on cassava production in Nigeria. Lagos State, though primarily urban, maintains active peri-urban cassava farming communities that supply fresh cassava to city markets. This study surveyed the incidence and severity of CMD in peri-urban cassava farms across five local government areas in Lagos State during 2023. Field assessments used systematic transect sampling, with disease incidence and severity scored using a standardised 1-5 scale. Seventy percent of farms surveyed showed CMD symptoms at incidence levels ranging from 31 to 78 percent. Enzyme-linked immunosorbent assay confirmed the presence of African Cassava Mosaic Virus and East African Cassava Mosaic Virus as the dominant viral species across sampled plots. Higher virus incidence correlated with the use of farmer-saved cuttings from previous seasons and proximity to abandoned cassava plots serving as inoculum reservoirs. Whitefly populations were consistently high across all surveyed areas, likely driven by warmer temperatures and the presence of alternative weed hosts in fragmented peri-urban landscapes. The study recommends a shift to certified virus-free planting materials and the implementation of community-level roguing campaigns to reduce CMD spread in peri-urban Lagos State farms. Keywords: cassava mosaic disease, begomovirus, Bemisia tabaci, Lagos, disease incidence.