Distances flown by Cicadulina spp. (Hem., Cicadellidae) in relation to distribution of maize streak disease in Rhodesia

Abstract

Distances moved by Cicadulina spp. were investigated at Salisbury, Rhodesia, during 1968–69, by using small plots of oats to trap adults dispersing from populations breeding in Pennisetum clandestinum or Eleusine indica grasses. The shape of the curves constructed for fall of numbers with distance confirmed laboratory findings that populations are composed of long and short distance fliers. The curve for numbers of infective Cicadulina punctures estimated from the gradient of maize streak infection falling from adjoining cereals was also of similar shape. Mean flight times indicated that a steep fall for about 10 m from source is due largely to short distance fliers making trivial movements, and the subsequent gentle fall is due to long distance fliers which may disperse many kilometres depending on the wind speed. There were higher proportions of long distance fliers amongst C. mbila (Naudé) compared to C. storeyi China, and amongst females compared to males dispersing downwind. A predominance of long distance fliers dispersing from drying grasses during April–September, and of short distance fliers present in irrigated grasses and cereals during October–March, causes seasonal differences in the patterns of maize streak infection and in the effectiveness of barriers of clear ground as a preventive measure.