The 'pink Niagara' grape (V. labrusca L. x V. vinifera L.) anomaly characterized by leaf chlorosis and "chocolate" (internal browning) of the young fruit, at first thought to be a virus disease, has been found to be a result of boron deficiency. The anomaly was first recorded in 1974. It occurs in patches in vineyards of Indaiatuba and Jundiaí, two grape-growing counties of the State of São Paulo, Brazil. Affected plants show yellowing between the primary and secondary veins of the upper leaves and malformed clusters, with normal-sized berries and small ones. Some small fruits are slightly elongated and show dark areas on the skin; many have dark brown pulp, easily visible when they are still green. Severely affected plants become stunted. Chemical analysis showed a lower boron content in the affected plants (18 ppm in the leaf blades and 7 ppm in the fruit) than in normal ones (24 ppm in the leaf blades and 10 ppm in the fruit). Leaf samples from three nearby vineyards without the anomaly presented a boron content of 35 ppm. Leaf blades from abnormal and normal 'Traviú' rootstocks (V. riparia Michaux. x V. rupestris Scheele x V. cordifolia Michaux., '106-8') had 16 ppm and 43 ppm B, respectively. An efficient control of the anomaly was got with borax, applied after prunning to affected plants at the rates of 5, 10 and 20 g per plant, or with boric acid at the concentrations of 0.3 and 0.6%a sprayed at flowering and when the fruits were small. There was a residual effect of the treatment on the anomaly for at least one more season.
Vitis spp.; physiologic anomaly; micronutrient; control