Among various diseases that can afflict citrus trees, fungus can be one of the most deadly. Citrus fungus that is not deadly is often unsightly, and may even cause the tree to produce less fruit or drop fruit prematurely. Fortunately, most fungus diseases can be treated simply by being aware they are there and taking the appropriate steps early enough. Though this may take extra effort, the possibility of losing a productive tree makes it worth the cost.
A number of citrus fungi will attack trees, depending on the area and the prevalence of the disease. Cotton root rot, melanose, greasy spot and sooty mold are a few of the more common fungal ailments attacking citrus trees. All have very different characteristics and may need to be treated in different ways. If you have trouble identifying the type of fungus infection you have, a local extension office can help.
Sooty mold is a fungal infection that makes the leaves of a citrus tree look black, or like soot. Melanose is a fungal disease often showing up as a scabbed fruit rind and is unsightly but often causes no real damage. Greasy spot produces brownish and yellowish spots on the underside of leaves, eventually causing leaf drop. Cotton root rot, common in Texas, attacks the root system and underground parts of a tree and will likely cause death quickly before symptoms can even be diagnosed.
Some fungal diseases may do nothing more than simply discolor or cause spots to appear on the fruit. It can still be eaten and will have no harmful effect on the tree. Sooty mold is one example of this. Other diseases, such as melanose and root rot can affect the entire tree if left untreated, eventually causing the tree to die and possibly spreading the same infection to other trees.
After the fungus has been identified, implement one of a variety of strategies to treat the current infection and prevent future ones. An anti-fungal spray meant for fruit trees may help in some cases. Root rot fungus will require the treatment of the soil around the tree. It is also important to remove any infected branches and leaves. If the fungus causes leaf drop, quickly take those leaves away from the area where the fruit trees are.
Though citrus trees prefer temperatures such as those mostly found in the southern portion of the United States, not all the diseases will be the same from location to location. Scab, for example, is not a big problem in Texas, but cotton root rot is. Therefore, your physical location may play a big role in identifying any disease and thus choosing a treatment plan for that citrus fungal infection.