FERTILISER GUIDELINES FOR THE WINE INDUSTRY

chlorosis, with areas around veins tending to remain green, with the result that the symptom upon later enlargement, strongly resembles a Mgdeficiency. Manganese chlorosis is always a yellow colouration, even in red cultivars (Fig. 21). The norms for Mn-contents of grapevine leaf blades and petioles are indicated in Table 15.

FIGURE 21: Mndeficiency symptoms in red (Grenache) and white cultivars are always yellow, finely divided, interveinal chlorosis (right) and strongly resemble Mgdeficiency symptoms (left).

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TABLE 15: Norms for the Mn-contents (mg kg -1 ) of leaf blades and petioles of grapevines.

Fruit set

Leaf blade

Petiole

Deficiency Sufficient High Toxic

Deficiency Sufficient High Toxic

<15

30-60 >250 >650

<20

30-60 >300 >1200

Veraison

Leaf blade

Petiole

Deficiency Sufficient High Toxic

Deficiency Sufficient High Toxic

<20

30-80 >300 >750

<20

30-60 >300 >1200

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