Here's a good article, there are different types and treatments mentioned here:
http://www.marinrose.org/chlor...
But this article
http://www.rosemagazine.com/fe... says:
Iron chlorosis, for example, is often treated by adding large amounts of chelated iron supplements to the soil. In this case, the symptom is yellowing leaves with dark green veins (leaf ribs). The cause of iron chlorosis is often high soil pH - a condition which traps existing iron in the soil, and prevents its use by the rose. The treatment, therefore, is not the application of supplemental iron, but rather the application of organic materials to bring the soil back into natural balance or slight acidification.
