Main Diseases of Avocado and Preventive Measures

1. Anthracnose disease

1.1 Symptoms of anthracnose disease

Anthracnose is an important disease of avocado, which mainly damages mature fruits, and can also infect leaves, twigs, flowers and young fruits, causing fruit drop and fruit rot. The disease usually occurs after fruit ripening, and the diameter of the lesions before fruit ripening does not exceed 5 mm, round, slightly sunken, brown or black. As the fruit matures, pathogenic bacteria can invade the pulp, causing dark green dry rot.

1.2 Prevention and treatment of anthracnose disease

Remove diseased branches in the orchard, cut off diseased leaves, eliminate the source of infection. Low-temperature pretreatment and low-temperature storage should be carried out as soon as possible after harvest. The key to prevention and control is to minimize the occurrence of other fruit diseases and avoid mechanical damage during fruit transportation.

2. Scab disease

2.1 Symptoms of scab disease

The affected fruit appears a slight round brown scar-like protrusion at the initial stage, and then turns brown to light purple. After the fruit matures, the lesions are combined, the center is depressed, and the peel is rough. The disease did not affect the flavor quality of the fruit, but the appearance quality was seriously reduced. In the young fruit stage, in case of cold and humid weather, the disease occurs seriously. Scab can also damage the leaves, brown spots appear on the affected leaves, the leaves shrink, the lesions further develop into a star shape, and the center is perforated. Leaf damage often occurred on the top of the tree crown, and the lesions were mostly within the leaf dorsal texture, and the lesions were small and discrete.

2.2 Prevention and treatment of scab disease

Cut off diseased branches to reduce pathogens and spray with Bordeaux mixture or other copper preparations.

3. Cercospora spot disease

3.1 Symptoms of cercospora spot disease

Cercospora spot disease can damage leaves, stems and fruits. When the fruit is infested, dead spots are formed on its surface or the epidermis is cracked, and the cracks can cause anthracnose infection. When the leaves are infected, 2-5 mm dead spots first appear on the leaf surface, which are brown at first, and then turn purple. The spots extend to both sides of the leaves, and the shape is irregular. In severe cases, the dead spots combine to form larger dead spots.

3.2 Prevention and treatment of cercospora spot disease

Using chemical control, spray copper preparations and azoxystrobin on branches and fruits.

4. Dothiorella fruit rot disease

4.1 Symptoms of dothiorella fruit rot disease

The symptoms of disease fruit were not obvious before picking, and the lesions were small and shallow, but the symptoms became obvious during the ripening process after the fruit was harvested and softened. Small and irregular brown to red lesions appeared on the peel at the initial stage. Due to the invasion of vascular bundles by the bacteria, brown streaks appeared on the pulp after peeling off the peel, and then purple-brown irregular lesions appeared on the pedicle. As the fruit matures, the epidermal lesions gradually become longer, darker and sunken, and the brown peel is covered with a layer of gray-brown mycelium and spores, and brown pulp and juice flow out, giving off an unpleasant odor.

4.2 Prevention and control measures of dothiorella fruit rot disease

Cut off diseased and dead branches, remove dead wood and diseased fruits, choose sunny weather for fruit picking, strengthen the nutrition of fruit trees, and reduce the occurrence of other diseases.

5. Stem-end rot disease

5.1 Symptoms of stem-end rot disease

The base of the fruit is first susceptible to the disease, with slight withering around the base of the fruit. As the fruit matures, the pathogen invades the fruit, and there is obvious black rot around the base, and then the boundary between the diseased and healthy parts is obvious. Finally, the rot gradually spreads over the entire surface of the fruit, and the fungus invades the pulp, causing tissue discoloration and an unpleasant odor, thereby reducing fruit quality.

5.2 Prevention and control measures of stem-end rot disease

Stem-end rot pathogens can survive on the diseased body of the host. Therefore, it is necessary to remove the source of infection in time to avoid the accumulation of sick and disabled bodies in the orchard. Watering in the lower parts of the orchard will prevent pathogens from moving to higher fruit. Elimination of water stress could reduces infestation. Covering film or weeds under the tree can promote the accelerated decomposition of the diseased body. In addition, do not harvest on cloudy and rainy days.

6. Phytophthora fruit rot disease

6.1 Symptoms of Phytophthora fruit rot disease

Phytophthora can cause fruit rot before and after harvest, as well as stem canker and rot. Infected fruits often have black circular lesions near the pedicle, and the fungus can invade the pulp.

6.2 Phytophthora fruit rot disease control measures

Cut off diseased dead branches and stems, clean up orchards, remove fallen and diseased fruits, and prevent re-infection by pathogens. Cover the plant with a thick mulch to prevent the spread of germs in the soil.

7. Soot disease

7.1 Symptoms of soot disease

Fruits, leaves and stems are covered with black soot-like hyphae and spores, and grow on honeydew secreted by wax scales and whiteflies.

7.2 Prevention and control measures of soot disease

The key is to control pests and reduce honeydew production. A better method is to use natural enemies for biological control.