THE TRANSMISSIOK OF STREAK DISEASE OF MAIZE BY THE LEAFHOPPER BALCLUTHA MBILA NALIDE

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Abstract
SUMMARY: In the absence of transmission of streak disease by the seed, the wide occurrence of this disease in maize in South Africa is accounted for by infection of the plants at some period after their appearance above ground. It has been shown that plants may be protected from infection by growing them in a greenhouse or under wire‐gauze of not less than 32 meshes to the inch.A number of insects have been tested as possible vectors of streak disease, and positive results have been obtained with a jassid, Balclutha mbila Naude. In four cases out of five, to each of which were introduced three or four adults of this species, collected on streak‐diseased maize, the disease developed in every plant. The plants hi three similar cages, to which no jassids were introduced, remained healthy.In experiments in which single individuals of Balclutha mbila, collected upon streak‐diseased maize, were allowed to feed upon single leaves of the experimental plants, the disease resulted in 46 out of 48 plants. One jassid lived for five months and carried the disease to eight separate plants. No loss of the power of infection occurred in any jassid tested, in spite of periods of starvation in some cases or of feeding on apparently immune plants in others. Certain individuals, collected upon streaked maize were incapable of causing any infection under similar conditions.Jassids reared upon healthy maize were incapable of infecting plants with streak disease. But after feeding upon a diseased leaf for a week, 26 per cent. of the males and 86 per cent of the females, out of a total of 62 individuals, became infective.Negative results were obtained in trials of Aphis maidis Fitch, Peregrinus maidis Ashmead and a number of undetermined jassids and fulgorids.Field observations showed that Balclutha mbila was to be found, although infrequently, whenever a field of maize, recently infected with streak disease, was thoroughly searched. It is held therefore to be the agent of spread of the disease in the field.

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