Iron deficiency does not come from a fungus or an insect; it is the result of a nutrient deficiency, which makes the plant struggle to carry out photosynthesis and produce chlorophyll.

Iron deficiency can be caused by excessive waterlogging or by too much lime in the soil, which prevents the plant from absorbing it properly.

It affects many plants, both ornamental ones such as rose, laurel, azalea, wisteria, and hydrangea, and fruit or vegetable crops such as citrus fruits, strawberries, raspberries, and peach trees.