The epidemiology of maize streak disease in relation to population densities of Cicadulina spp

SUMMARY The effect of population density of Cicadulina spp. in maize on the epidemiology of maize streak disease was investigated for irrigated crops planted in March or July at Salisbury, Rhodesia, from 1967 to 1969. Experimental plots of maize were invaded for 2–3 months following germination by Cicadulina adults leaving drying veld grasses. When there were few immigrant leaf‐hoppers, incidence of maize streak increased arithmetically through transient settling and feeding of previously infective adults. Infection rates increased when infected plants were removed daily, presumably because of the disturbance of vectors. By comparison, large immigration populations (one leaf‐hopper per three maize plants) resulted in an exponential increase in the incidence of maize streak infection. Aldicarb granules (10%) at 38 g per 12 m row length, applied into a furrow before planting the maize, gave almost complete protection from infection.