The lemon tree is perhaps the most popular of citrus fruit trees cultivated the world over. Diseases that attack this tree may be viral, bacterial or fungal in nature. Most of them are not fatal. However, it helps to recognize symptoms early and take appropriate action. You can ensure the continued good health of your tree if you maintain a keen eye for any disease outbreaks. Following is a guide to help you identify and manage lemon tree diseases.
This bacterial disease causes leaves and fruit to drop off prematurely. Holes develop on the leaves which gradually turn brown. The fruit also becomes brown and develops bumpy areas with a water-soaked or oily yellow margin. Although the tree is unlikely to die, citrus canker causes a significant decline in health. Fruit yields are reduced and affected trees eventually cease to produce any fruit. Citrus canker is a highly contagious disease. Sharing garden equipment, severe storms and strong winds are likely to spread the infection rapidly. Spray with a copper fungicide immediately you notice the canker. However, trees that are severely infected need to be uprooted and destroyed.
Yellow Dragon Disease
It is a bacterial disease mainly spread by insects. Infected trees become yellow and weak. Leaves may become mottled. Fruit remains small and looses shape. Quite often ripened fruit will retain some green color. Uproot and dispose of any infected trees as this is the most effective way of control.
Also known as root rot, this is a fungal disease caused when spores from the ground attack the trunk. It spreads more rapidly during severe storms. Brown patches of toughened bark develop on the tree trunk. Sap may ooze from the infected area. Mature fruit develop brown lesions with a strong odor. Foliage and blossoms also turn brown and decay. Gather and dispose of all infected leaves and fruit as they fall off the tree. Cut off low-hanging branches to help check the spread. Use a copper fungicide to spray affected parts immediately you notice symptoms. Repeat spray application after two seasons.
This is a fungal infection. Decomposing leaves on the ground underneath the tree develop airborne spores. These reproduce and transfer onto the tree through lower leaf surfaces. After an incubation period of several months black spots develop on the leaves. The tree experiences leaf loss which increases with time. Greasy spot is encouraged by warm and damp conditions. Gather and dispose of all fallen leaves. Spray with a liquid copper fungicide once in the summer and repeat in the fall.
This viral infection is spread by aphids. Grafting trees on vulnerable rootstock is likely to encourage the disease. Citrus tristeza causes wilting of trees, leaves become yellow and curly, and the tree remains dwarf-sized. Fruit yields also decline. It can be fatal if it causes a blockage of the circulatory system, leading to the death of the tree. Prevention is the best strategy in managing citrus tristeza. Choose healthy rootstock that can withstand the disease. Otherwise, spray infected trees with an insecticide to eliminate the aphids. This will help contain the spread of the disease.