Identification of insect vectors of maize lethal necrosis viruses and their virus-transmission ability in Ethiopia

Maize lethal necrosis (MLN) is a viral disease caused by co-infection of Maize chlorotic mottle virus (MCMV) and a potyvirus mostly Sugarcane mosaic virus (SCMV). MLN is one of the most important maize production constraints in East Africa including Ethiopia. In this study molecular characterization was used to determine potential insect vectors that transmit MLN causing viruses in Ethiopia. Suspected insect vectors of MLN causing viruses collected from maize fields were initially identified to a genus/species level based on the morphological features. Further taxonomic determination was carried out using DNA sequencing from cytochrome oxidase primers. Pre-identified insect vectors of MLN-causing viruses were separately tested in the greenhouse for potential transmission of MCMV and SCMV. Accordingly, maize thrips, Franklinella sp. (Thysanoptera: Thripidae) and cereal leaf beetle, Oulema sp. (Coleoptera: Chrysomelidae) transmitted MCMV, whereas corn leaf aphids, Rhopalosiphum maidis Fich (Hemiptera: Aphididae) transmitted SCMV. Out of 86 maize fields surveyed, Franklinella sp. were widely distributed in 22 (25.6%) fields, mostly in Arsi and West Shewa zones of Oromia region. R. maidis was abundant in all the areas assessed, suggesting that this insect spp. is a vector for SCMV in Ethiopia. The presence of insects as vectors of MLN causing viruses on maize plants is believed to contribute to the widespread of MLN viruses from plant to plant, field to field and to new geographical areas. Thus, managing these vectors through appropriate control measures can reduce maize yield losses caused by MLN disease.