Yellow leaf of citrus is caused due to

✅ Explanation
Molybdenum (Mo) deficiency in citrus is commonly called “yellow spot.”
The deficiency occurs when trees are unable to absorb sufficient Mo from an acidic soil.
Deficiency symptoms appear on the leaves as large, interveinal chlorotic spots in early summer.
As the leaves age, the yellow spots develop deposits of brown gum on the lower leaf surfaces, which may eventually turn black.
In many cases, an infection of anthracnose causes the areas covered by the spots to die and drop out, leaving small holes in the leaves.
Affected leaves eventually drop, and trees become almost defoliated during the winter.

🔑 Important Points
→ Molybdenum deficiency is marked by yellow spots on citrus leaves.
→ Interveinal chlorosis appears in early summer.
→ Brown gum deposits may appear on the lower leaf surfaces.
→ Anthracnose infection can cause areas of the spots to die and drop out.
→ Affected leaves drop in the winter.

📝 Prevention:
Mo deficiency can be easily corrected with a sodium molybdate or ammonium molybdate foliar spray.
If the spray is applied between summer and early fall, the leaves will re-green, and the yellow spots will disappear from the upper surface.