VIRUS INDUCED CHANGES IN THE GROWTH OF POME FRUIT TREES
Pome fruit cultivars and rootstocks differed greatly in their sensitivity to the viruses; pears were usually less tolerant to infection than apples and no virus spread occurred in any of the experiments.
Many characteristics of the trees were changed by the viruses; most were reduced in vigour and trees were less uniform. Some infections rendered the crop unsaleable or markedly reduced crop weight and fruit size. In a few cultivars some infections increased fruit colour and improved the crop to trunk girth ratio.