I live in Spain, and this year my orange tree has turned yellow all over, with no flowers or fruit. What could it be? I have taken a picture.
As you may know, plants can be victim of different kinds of affections :
- Nutrients deficiency
- Parasits assaults
- Meteorological perturbations
First of all, you should check for parasits, even if I don't think the leaf color is caused by a predator or a disease. Return a leaf, better with a magnifying glass, and try to spot living / moving creatures. For example, aphids look loke little black dots and make leaves sticky.
Secondly, find information about citrus culture in your specific region (if you live in Andalousia or in Galicia, climate change from oceanic to mediterranean). Yellow but not dry leaves are often caused by too wet soil (bad water extraction, too much rain...).
At last, check for agrum tree deficiencies. In my opinion, this is a nitrogen deficiency. Treat with some grow fertilizer or, if you prefer more natural way, ashes, nettle manure or garden compost. This link can give you an idea on how to diagnosis affliction, but you should find something more accurate for your citrus.