MOSAIC DISEASES OF THE CUCUMBER*

Summary. Three cucumber mosaic diseases of this country and the causal viruses are described. The first disease, green‐mottle mosaic ( cucumber virus 3), and the second, yellow mosaic ( cucumber virus 4), are not transmissible to solanaceous plants. Cucumber virus 3, on cucumber, causes a dark green mottle with blistering and distortion of the leaves, but the fruit is not usually marked; while cucumber virus 4 gives rise to a distinct type of leaf‐mottle, yellow to silver‐white in colour, and the fruit may be seriously marked. The third disease, yellow‐mottle mosaic ( cucumber virus 1), is characterised by a diffuse yellow mottle of cucumber leaves and fruit and is transmissible to solanaceous plants. Cucumber viruses 3 and 4 are described for the first time. Notes are given on fern leaf of tomato, insect vectors and control measures.