Kiwifruit Nutrition diagnosis of nutritional disorders
The following section is devoted to a number of important leaf symptoms caused by factors other than mineral nutrition which have not been covered in detail elsewhere36.
Glyphosate injury to young kiwifruit plants results in elongated and distorted leaves (Photos 23a and 23b). Frequently the tissue between the minor veins is ridged upwards and in some cases the affected leaves may be chlorotic (Photo 23a).
On mature vines, which are considered to be more tolerant than younger plants43, injury symptoms appear first on young leaves of actively growing canes. Symptoms include a bright yellow chlorosis which develops at the leaf margins and spreads inwards between the veins towards the midrib, often leaving a zone of healthy tissue each side of the main veins (Photo 23c).
In many respects these symptoms are similar to those caused by deficiencies of manganese and magnesium. However, an important point of difference is that symptoms of glyphosate injury appear first on the youngest leaves and not on recently matured leaves as with manganese deficiency or on the older leaves as with magnesium deficiency. Unlike the effects on the younger plants, the shape of the leaves on mature plants remains undistorted (Photo 23c).
Studies with other plant species have shown glyphosate is readily translocated from the point of absorption to active growth points within the plant46. More recently, investigations with peach trees have shown that fruit yields are reduced the following season unless affected limbs are pruned immediately after spray contact51.
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| 23a | 23b | 23c |
Caragard injury produces a characteristic veinal chlorosis which appears first on the older leaves (Photo 24a). The main veins of the leaf are affected first, but the chlorosis spreads quickly to the secondary veins (photo 24b).
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| 24a | 24b |
Amatin injury results in severe scorching of older leaves (Photo 25a). The necrosis usually begins at the leaf margin causing the leaf to curl up as the affected tissue dries out (Photos 25b and 25c). In severe cases the whole leaf becomes necrotic (Photo 25c).
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| 25a | 25b | 25c |
Simazine injury produces a characteristic bleaching of the margins of the older leaves (Photo 26a). As the injury becomes more pronounced the tissue between the veins may also become bleached. However, even on severely affected leaves the major veins remain conspicuously green (Photo 26b).
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| 26a | 26b |
2, 4-D injury causes distortion of the leaves which are often cupped upwards (Photo 27a), or downwards (Photo 27b). Although there is no noticeable reduction in leaf size, the tissue between the main veins is often ridged upwards. There is no loss of pigment from the affected leaves. Plants contaminated with 2, 4-D in the autumn can exhibit distortion of the leaves and fruit the following season36.
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| 27a | 27b |
2, 4, 5-T injury is characterised by a marked reduction in leaf size and a distortion of leaf shape (Photo 28a). As the injury becomes more pronounced the internodes of the new canes fail to elongate, giving the plant a stunted appearance (Photos 28b and 28c).
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| 28a | 28b | 28c |
