FERTILISATION GUIDELINES FOR THE TABLE GRAPE INDUSTRY

CHAPTER 5

FIGURE 23: For older leaves B deficiencies lead to interveinal, chlorotic yellowing and uneven chlorotic spots, as well as millerandage bunches with small, seedless berries (Photo: D. Saayman).

Boron toxicities are sometimes observed, with symptoms that correspond in many ways to those of deficiencies. It results in thin shoots with strong lateral growth and consequently a bush-like appearance. The excess B tends to concentrate in leaf edges, leading to arrested growth of the edges of apical leaves and leaf teeth not developing, while the middle parts continue to grow causing the leaf to curl downwards and display a knobbly, smooth-edged appearance (Figure 24). On older leaves necrotic specks develop and, similar to a B deficiency, berry shattering and millerandage-like berries develop.

FIGURE 24: B toxicity lead to loss of serration (teeth) and knobbly appearance of leaves (left), as well as irregular chlorotic blemishes and necrotic lesions (right) (Photos: P. Raath (left); D. Saayman (right).

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