RESPONSE OF LITTLE CHERRY-INFECTED CHERRY TREES TO ZINC TREATMENTS
In the Creston Valley of British Columbia, mature Lambert cherry trees displaying severe symptoms of the virus disease little cherry were treated with various zinc carriers applied to the soil, to the dormant wood, or to the foliage. The trees had not shown the chlorotic symptoms typical of zinc deficiency but had produced fruits and leaves that were smaller than might be expected from the virus infection alone.The zinc treatments invariably resulted in improvements in leaf size, and especially in fruit quality. The best zinc treatment gave increases of 59 per cent in fruit size and 77 per cent in soluble solids content. The most marked responses were obtained with zinc sulphate applied as a dormant spray or with ZnEDTA chelate applied to the soil. Foliar sprays were the least effective. The quantity of zinc present in the leaves collected from treated plots showed no association with observed fruit responses. Leaf analyses demonstrated that a mild zinc deficiency condition existed. These trials indicate that the quality of fruits on trees infected with little cherry virus may be adversely affected by zinc deficiency, in the absence of recognizable zinc deficiency symptoms.