Spatial and temporal spread of maize lethal necrosis disease causing viruses and their vectors within the field

Maize lethal necrosis disease (MLND) is a viral disease of maize resulting from co-infection of Maize chlorotic mottle virus (MCMV) and any cereal Potyvirus such as Sugarcane mosaic virus (SCMV), Maize dwarf mosaic virus (MDMV) or Wheat streak mosaic virus (WSMV). It was first reported in Kenya in September 2011 in Bomet County with a yield loss of 90 – 100%. Since its first report, efforts have been directed towards causal viruses, vectors and possible management options. The present study aimed at determining the spatial and temporal distribution of MCMV and SCMV causing MLND and their vectors within the field. Two maize varieties; H614 and Duma 43 were grown and managed in non-replicated plots at the University of Nairobi, Upper Kabete Campus Field Station. The plants were naturally infested with vectors and infected by MLND causing viruses. Vectors abundance on plants was assessed by counting techniques and sticky traps at two weeks interval. Twenty maize leaf samples per variety both asymptomatic and symptomatic were collected at two stages (knee high and prior to flowering) of crop development to confirm the presence or absence of MCMV and SCMV using DAS-ELISA. In the study, vectors began infesting the crop from 3rd – 5th weeks after emergence. Aphids were observed in colonies (on a few plants) in patches while thrips were evenly distributed within the field. In both cases there were no differences in infestation of the two varieties by the vectors. A single peak was observed for aphids while two peaks were observed for thrips during the growing seasons. For maize leaf samples tested, nine samples from H614 and eight samples from Duma 43 tested positive for MCMV, while three samples from H614 and one sample from Duma 43 tested positive for SCMV. Though Kabete is not an MLND hotspot area, the viruses associated with MLND were present.