I can see this topic has been done over and over again but my case is slightly different than the others. This tree is about 5 years old, my grandmother gave me two seedlings she found inside one grapefruit she had bought. One died in its first year from frost and the one that survived did barely. Unforunately it has been dropping leaves for the last year or so. They turn yellow along the vein and slowly moves out until the leaf drys out and drops. At the end of this last winter it grew a bunch of leaves at the top and a few at the bottom. The main stalk dropped all leaves about 6 or 7 months ago. I haven't been able to identify any pests or disease and attributed it to overwatering, which I used to do once a day until all the soil was visibly moist. It was fine with it until about a year ago. Any help will be greatly appreciated.
When was the last time you changed the soil or gave this tree new soil? When you wrote that you watered this tree every day, about how much water were you applying? How often have you fertilized this tree and what kinds of fertilizer have you been using? You have a severe zinc deficiency which is causing the leaves to appear way too small in size but you will also can get a brownish colored lesion (you can see a typical lesion to the right of your thumb in your HPIM0338.jpg photo) to show up on the interior of the leaf, then soon see a fast acting chlorosis and then the leaf dries up and falls off. You will want to locate a zinc chelate and use it as a foliar spray but you will also need to use a ground based fertilizer program (more often if you are using one now) using either a commercial granulated Citrus food or a series of applications of a liquid fertilizer such as MirAcid and MiracleGro. There is a lot of truth in the title of this link below. http://www.uni-hohenheim.de/i3ve/00068900/18920041.htm Jim
I repotted the plant to its current pot about 3 years ago, since then nothing has been added or changed. It was standard potting soil you'd find at any store, it was a quick fix I didn't initially intend to leave but did. As for the water, it was probably no more than 1/4 of a gallon. The container I used to use is long gone but it was a gallon itself, and if memory serves I used only a 1/4 of it and the rest for portions of my garden that didn't have a drip system. For fertilizing, I never have done it. I didn't know what I should be using and since it wasn't showing any problems I never bothered. But obviously there is a problem and I need to start doing it. Many thanks for your time.
