Boron deficiency (B)
Lack of boron will show as a diffuse yellowing between leaf veins. Leaves will show a tendency to crumple downward. Leaf blades will swell; leaf edges may show signs of dieback. These symptoms will first appear on young leaves.
Boron deficiency may cause stunted branch meristem growth. Typical symptoms on grapes are dropping and dried out bloom and `shot grapes´.
Treatment: If the soil is low in nutrients it is advisable to apply boron fertilisers in the spring. As soon as deficiency symptoms appear on leaves or during dry spells (which significantly raise the risk of boron deficiencies) foliar fertilisation with EPSO Microtop® (0.9 % boron) is recommended.