Avocado trees can decline in health from a number of cultural and environmental problems. You can prevent many problems by planting your avocado tree in a location that meets its growing requirements. Trees will not produce healthy growth if they are planted poor draining soil or in soil that has a pH outside of their preferred range, according to Texas A&M University's website. Diseases such as anthracnose and scab can compromise the health of the avocado tree.
Poor Draining Soil
Avocado trees have little tolerance for being planted in poorly draining soil or areas where flooding occurs. A tree grown in poorly draining soil is susceptible to diseases such as root rot. Root rot is a fungal disease that causes yellowing leaves, branch dieback, defoliation and a decreased avocado yield, according to the University of California's website. Gardeners may be able to control the disease by applying phosphite fungicides in the late spring or summer months. Remove the tree and avoid planting in the area if you cannot control root rot with fungicides.
Soil pH Range
Avocado trees prefer a soil pH range between 6.0 to 6.5, according to the California Avocado Commission's website. Trees grown outside of this range are unable to absorb the nutrients in the soil. You may see your tree experience yellowing leaves, stunted growth or overall declining health. Dig a 6-inch hole next to the avocado tree and perform a soil pH test. Lime the area if the soil's pH is under 6.0. Spread sulfur over an area if the range is above 6.5. Retest the area in three months.
Anthracnose is a serious fungal disease caused by colletotrichum gleosporioides fungal spores, according to the University of Florida's website. Symptoms consist of fruit lesions, which cause sunken areas, browning and black spots. As the disease progresses, lesions begin to crack and the entire fruit is can decay. Diseased areas of the tree should be pruned off and all diseased debris should be removed from the growing location. A copper compound can be applied to prevent future occurrences of anthracnose.
Scab is caused by sphaceloma perseae fungal spores, according to the University of Florida. Avocados with the disease produce spots that are brown to purplish-brown in appearance. These spots coalesce and sink into the fruit. The area around the sunken spots become rough. Generally, gardeners will see the upper portions of their avocado tree exhibit symptoms of scab. Check the tree in the spring for scab. The disease quickly germinates and spreads during moist cool weather conditions. Apply a fungicide to treat scab disease.
- Texas A&M Cooperative Extension; Home Fruit Production Avocadoes; Julian W. Sauls
- University of Florida Extension; Diseases of Avocado in Florida; Ken Pernezny and R. B. Marlatt
- University of California Agriculture and Natural Resources; Management Guidelines for Avocado Root Rot; August 2008
- California Avocado Commission; Growing Avocados
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