FERTILISER GUIDELINES FOR THE WINE INDUSTRY

FIGURE 22: General Mntoxicity symptoms (left) with small black spots concentrated on nodia.

As foliar nutrition, a 0.4-0.6%-Mn-sulphate solution can be sprayed. By add ing urea (0.5%solution), the efficacy of uptake is increased. The use of Mn containing fungicides may suppress latent Mndeficiencies, but is not sufficient in the case of visible deficiency symptoms. Manganese toxicities have been observed in grapevines in the Breede River valley on red-brown higher-lying terrace soils containing abundant Fe-sulphides (pyrite), which oxidise to sulphuric acid, acidifying the soil and resulting in high Mn-contents. Symptoms are shrivelled, thick, curled-up leaves with raised, pin head sized, black spots on shoots, which are especially concentrated on the internodia (Fig. 22). Berry shattering and millerandage of bunches also occur.

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