Lemon trees produce fruit that has a heavy fragrance and is used in a variety of cooking dishes. When grown in the home garden, tending to a lemon tree can be difficult. There are a variety of diseases that affect lemon production. Understanding the main causes and varieties is essential to prevention and treatment.
Parasitic diseases are caused by fungi who feed off of the lemon tree, causing wilting and weakness in the tree. Phytophthora foot root is a common parasitic disease, especially in trees that have grafted branches from the propagation process. Bark becomes weak and is easily removed. Branch wilt is another common parasitic disease that attacks when areas of the tree are damage by sun or wind. It causes the wood to look burned and wilt. Fruit rots are also possible where the fruit is attacked by the fungi, causing the fruit to wilt or fall off.
The citrus nematode is a parasitic infestation. Nematodes are micro organisms that collect around the roots of the tree. Infected trees may appear normal for several years, says the University of Arizona Extension, before the tree begins a decline. Infected roots stop growing and reduce the nutrients and water absorbed from the soil by the tree. This reduces the tree yield and quality of fruit. Leaves begin to yellow, and fruit looses its uniformity.
Sooty canker is another fungal disease that affects lemon trees. It is caused by the fungus Hendersonula toruloidea and occurs when a lemon tree is sun burned. The fungus infects the sunburned sites. Sunken lesions occur and black masses of spores appear under the tree bark. Limbs of the tree fall off and die. Infected limbs require pruning immediately to prevent spread.
Trees that are infected require removal immediately. Any areas that were infected with fungal diseases should never be planted until the area is fungal free. Disease resistant varieties are available and should be planted when possible. Preventative fungicides are sprayed in the spring, and bi-weekly throughout the season to prevent fungal diseases.
Control of Parasitic Disease
Control of parasitic disease starts will proper care. The tree requires regular fertilization to ensure strong root development and bark growth. If fungus develops on the tree, fungicides are available that attack specific fungal diseases. Proper identification of the fungus determines which fungicide is used. Many university extension offices provide tests to determine the fungal variety. Removal of wood that infected reduces the spread of the parasitic disease.