Q. I have 9 orange trees on my property and pamper them like my “kids”. One of them (perhaps two) is losing the green color in the leaves although the veins are staying green in color. I would like to send you a couple of leaves for your inspection as I have tried to trouble shoot the problem using the computer and pictures. A local nursery disagrees with my request for manganese sulfate to resolve the problem. Would you send me an address so that I can send a few leaves for your inspection and suggestions?
A. A picture of the leaves will work just as well as sending me a sample. I will be out of the country and so samples will probably not reach me.
Nine times out of 10 a yellowing leaf with green veins, particularly if it is the newer growth at the ends of the branches, is iron chlorosis and not typically manganese or zinc. The manganese sulfate would be used for a manganese deficiency or you could use a manganese chelate.
You can sometimes take an iron solution with a few drops of Ivory liquid detergent and, making sure the iron solution is slightly acidic with a little bit of vinegar, dip the leaves in the solution for a few minutes. You should see a color change in the leaves in about 24 hours or less.
Otherwise you can take some liquid iron chelate with a little bit of detergent like Ivory liquid and spray the leaves three or four times over a period of a couple of days. This will also turn them a darker green if it is iron.
If it is something other than iron, it won't do anything. Then go ahead and try your manganese application.
If this color change occurred during the winter it is possible it could be cold damage. This appears more like a bronzing of the leaves rather than yellowing. I hope this helps.