Symptoms
Symptoms always start on youngest leaves with yellow green, later pale yellow interveinal chlorosis. Main veins remain green. The blades show the most severe fading at their margins.
Severe deficiency produces symptoms on older leaves and entire shoots, too.
Usually the first leaves formed in the spring do not suffer; only later growth is chlorotic.
Reasons
Iron deficiency
An actual lack of Fe is rare because most soils contain enough Fe to meet the requirements of grapevines. However, the low availability of Fe creates deficiencies (lime-induced chlorosis).