The epidemiology of maize streak virus disease (MSVD) has been studied in Uganda by a collaborative project involving the Cereals Programme of the Ugandan National Agricultural Research Organisation and Natural Resources Institute of the UK. The incidence of MSVD in maize plots was monitored weekly and vectors monitored daily using yellow sticky traps, weekly visual counts, and the use of suction devices. Yields were recorded and specific experiments carried out to examine vector behaviour. Results showed that: The majority of vectors (Cicadulina spp.) caught on the sticky traps were males, and were caught within 50cm of the ground, regardless of the height of the maize. The majority of those caught in suction devices (sampling the canopy, particularly the whorls) were females. There was a greater incidence of streak in the shade due to vector preference for shade. The Cicadulina showed a clear preference for maize plants 25-40 cm high and they also tended to select weaker plants to settle on later in the season. These results tend to suggest that males move through the maize crop at low levels in search of females, which are usually found in the whorls. Acoustic signalling through the maize stems is used to locate the females. The finding of females in a maize crop must be considerably easier than in the denser vegetation presented by most wild grasses that are preferred hosts for feeding and oviposition. This may explain why Cicadulina are often found in large numbers in maize and low numbers in wild grasses. Cicadulina appear to select or avoid maize plants at different stages in growth as well as preferring to settle on shaded plants. This may affect the distribution of MSVD in plots and also yield results.

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0103|AL-Maize Program|AGRIS 0102|AJ

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