Groundnut Rosette Disease in Tanganyika

Rosette disease of groundnuts in Tanganyika is brought into the crop by infective alatae of Aphis craccivora: spread within the crop is by apterae and alatae. During the dry season the aphids maintain themselves on self‐set groundnuts and on two genera of Leguminosae: Vigna and Millettia or Lonchocarpus. No native source of the virus causing rosette disease has been discovered, but self‐set groundnuts carry over the virus from one cropping season to the next. Syrphid larvae and other predators are important in controlling the vector. Preliminary spraying trials with 0.5% schradan gave promising results in controlling the aphids on groundnut crops and consequently checking the spread of rosette disease. Selections of the variety Mwitunde showed the lowest incidence of rosette infection and gave the highest yields in trials in 1952.