Common diseases of avocado and their control methods

Avocado is light and fragrant, and can be eaten after peeling. Their flesh is relatively hard, contains less water and tastes like butter, so they are also called avocados. . There are many pathogens of avocado fruit diseases, most of which are fungi. So how to prevent avocado diseases? Next, I will introduce the common diseases and prevention methods of avocado.

Common Avocado Diseases and Control Methods: Anthracnose

Anthracnose is an important disease of avocado, which mainly harms mature fruits and can also infect leaves, branches, flowers and young fruits. Causes fruit drop and fruit rot, and shortens the shelf life.

Generally, the disease occurs after the fruit ripens. Before the fruit ripens, the lesion is less than 5mm in diameter, round, slightly concave, brown or black. When the conditions are suitable, the lesion spreads rapidly, the depression is obvious, and radial cracks appear in the center of the lesion; Finally, the diseased spots are connected together and pink conidia piles appear. As the fruit matures, pathogenic bacteria will invade the pulp, leading to dark green dry rot.

The pathogen is Colletotrichum gloeosporioides. Belonging to the class Colletotrichum gloeosporioides.

Pathogens grow vigorously on PDA medium, and the colonies are gray in the early stage and dark gray in the later stage. Conidia (7 ~ 20)? M X 2.5？ M, single cell transparent, cylindrical or oval (one end is flush and the other end is protruding). Acervulus is irregular in shape, transparent at first, then light brown, with an average diameter of 500? m； The bristles are brown, (4 ~ 8)? M X 200？ M, 1~4 septa, needle-shaped, slightly enlarged at the base and gradually tapered at the top.

The pathogenic bacteria are weakly parasitic bacteria, which mainly invade through wounds caused by pathogens such as wind and insects. Pathogens lurk in immature fruits and get sick when the fruits are ripe. Its spores can germinate to form infection nails and invade the peel. M, and then stay still; Until avocado ripens, when the lipoxygenase activity in the peel decreases, pathogenic bacteria reactivate and invade the fruit, causing postharvest rot.

Prevention and control methods: remove diseased branches from orchards, cut off diseased leaves and eliminate the source of infection. Postharvest low temperature pretreatment and storage should be carried out as soon as possible. All avocado varieties are sensitive to this pathogen before eating. The key to control is to minimize the occurrence of other fruit diseases (especially cercospora leaf spot) and avoid mechanical damage in fruit transportation.

Common Avocado Diseases and Control Methods: Scab Disease

The damaged fruit produces a slight round brown scar at first, and then turns from brown to light purple; When the fruit is ripe, the disease spots are combined, the center is sunken and the peel is rough. After the disease infects the fruit, its flavor quality is not affected, but its appearance quality is seriously reduced. In the young fruit period, the disease is serious in cold and humid weather. It can also harm the leaves, and the damaged leaves appear brown spots and the leaves shrink; The lesion further developed into a star shape with a central perforation. Leaf damage often occurs at the top of the tree crown, and the lesion is mostly at the back texture of the leaf, which is small, discrete and discontinuous and difficult to observe. The lesions on petioles and branchlets are oval, which are easily confused with those caused by scale insects. The sensitivity of different varieties to the disease is quite different.

The pathogen is coccidioides persica. , belonging to the genus Colletotrichum.

Conidia (2 ~ 30)? mX(2~5)？ M, oval, single cell transparent; Conidia are terminal or lateral, and the medium is olive to yellowish brown.

Pathogens can survive in diseased stems and leaves. Under the conditions of high humidity and low temperature, pathogenic bacteria easily invade shoots, leaves and fruits, form special scab spots and produce a large number of conidia. Spores are spread by wind, rain, dew or insects. Young leaves are susceptible to diseases, and old leaves have strong disease resistance.

Prevention and control methods: cut off diseased branches to reduce germs. Spray Bordeaux mixture or other copper preparation.

Common diseases of avocado and their control methods: gray spot disease

Can harm leaves, stems and fruits. Infected fruit will form withered spots on its surface or cause skin cracking, thus causing anthracnose infection. When infecting the leaves, firstly, 2 ~ 5 mm withered spots appeared on the leaves, which were brown at first and then turned purple, and the spots spread to both sides of the leaves with irregular shapes; In severe cases, the dead spots merge to form a larger dead spot.

The pathogen is pseudosporium purpurea. It belongs to Cercospora.

Conidia (2 ~ 4.5)? mX (20~ 100)？ M, inverted rod, light olive, 1 ~ 9 septa, with one end bent and one end gradually bent. Conidiophore (3 ~ 4.5)? mX(20~200)？ M, septate, erect and rarely branched, slightly knee-bent, light olive to olive. On H3A medium, the hyphae were gray, and then changed from brown to dark brown.

At first, the leaves were damaged, and bacteria invaded the host tissue through the wound or directly, and spread from the lower leaves to the upper leaves. In the warm and humid season, bacteria are prone to produce a large number of conidia, which are spread by wind, rain, insects or irrigation water. Mature fruits are more susceptible to diseases than small fruits and nearly ripe fruits.

Control method: chemical control, spraying copper preparation and azoxystrobin on branches and fruits.

Common diseases of avocado and their control methods: small hole shell fruit rot

Before picking, the symptoms of infected fruits are unknown, and the diseased spots are small and shallow. Symptoms become obvious during fruit ripening, and small and irregular brown to red spots appear in the initial peel. Because bacteria invade vascular bundles, you can see brown stripes when you peel off the skin. As a result, the pedicle appears purple-brown irregular lesions. As the fruit ripens, the epidermal lesions gradually turn black and droop. The fruit is shriveled, the brown peel is covered with a layer of grayish brown mycelium and spores, the fruit rots, and the brown pulp and juice flow out, giving off an unpleasant smell.

The pathogen is Botryosphaeria sp., which belongs to the genus Ascomycetes, and the asexual generation is Pleurotus fungi.

Spores of pathogenic bacteria thrive on dead branches, dead leaves, fallen fruits and stems, spread with wind and rain, and invade fruits through wounds and lenticels. Latent infection has occurred in the orchard, and the symptoms gradually appear and develop when the fruit is harvested and matured.

Prevention and control methods: cut off dead branches and remove dead trees and diseased fruits. Choose sunny weather to pick fruits. Strengthen the nutrition of fruit trees and reduce the occurrence of other diseases.

Common diseases of avocado and their control methods: stem rot

The pedicel of the fruit comes on first, and there is slight withering around the pedicel. As the fruit ripens, the pathogen invades the fruit, and there is obvious black rot around the fruit pedicle, and the boundary between the diseased and healthy parts is obvious. And gradually expand.

Until the whole fruit surface, bacteria invade the pulp, causing discoloration, degradation and unpleasant smell of the tissue, thus reducing the quality of the fruit.

The types of pathogenic bacteria are complex, including botrytis cocos, botrytis pyriformis, botrytis parvum, botrytis polyspora, botrytis aromatica, Phomophilum pseudostemon, pseudothyroid, Colletotrichum gloeosporioides and botrytis acuta.

Germ spores are produced on dead leaves, twigs and branches and spread with the wind and rain. Spores lurk in the stems of avocados and infect fruits from wounds or pedicels. The symptoms of fruit are not obvious when it is green; The fruit is fully mature and the infection symptoms are obvious. Water stress will promote the infection of fungi, and the cold storage environment will also accelerate the infection of anthracnose and Phomophilus pseudopedunculata.

Control method: The pathogen Hanergy parasitizes on the sick and disabled body of the host. Therefore, it is necessary to clear the source of infection in time to avoid the gathering of sick and disabled people in the park. Watering the lower part of the orchard can prevent bacteria from transferring to higher fruits. Eliminating water stress can reduce infection. Covering trees with film or weeds will accelerate the decay of the sick and disabled. In addition, don't harvest in rainy days.

Common Avocado Diseases and Control Methods: Phytophthora Fruit Rot

Phytophthora can cause fruit rot before and after harvest, and can also cause stem ulcer and rot. Infected fruits often have black round spots near the pedicle, and germs can invade the pulp.

The pathogens are apple scab, apple scab and so on. It belongs to the genus Phytophthora belonging to the class Oomycetes of Flagellainae.

This disease is prevalent in the rainy season. Phytophthora spores enter the fruit from the soil through heavy rain or spraying water.

Prevention and treatment methods: cut off the diseased dead branches and withered branches; Clean up the orchard, remove fallen and diseased fruits, and prevent pathogens from being infected again. Cover plants with thick mulch to inhibit the spread of pathogens in the upper soil.

Common avocado diseases and their control methods: coal smoke disease

The surfaces of fruits, leaves and stems are covered with a large number of black soot-like hyphae and spores, which grow on the honey dew secreted by wax scale and whitefly.

The pathogen is Capnodium sp., belonging to the genus Ascomycetes.

Generally, soot bacteria will not invade the fruit and cause harm, but will affect the appearance and quality of the fruit. If the leaves are covered with too thick soot, photosynthesis will be inhibited, leading to the withering of leaves and early shedding.

Control method: The key is to control pests and reduce the production of honeydew. At present, a better method is to use natural enemies for biological control.

Common diseases of avocado and their control methods: other fungi and bacteria causing postharvest rot

Include Alternaria, Penicillium and Fusarium. , polychaete, Trichophyton pink, Rhizopus stolonifera, Pseudomonas syringae, etc.

Common diseases of avocado and their control methods: sunburn

Avocado sunburn was originally considered as a physiological or hereditary disease, and 194 1 year proved that it can be spread by grafting, and it is a disease. At the end of 1970s, it was confirmed that the pathogen was a virus-like virus, namely avocado day spot virus (ASBVd), a single-stranded circular RNA molecule with 247 nucleotides. Avocado mouth burning is distributed in Australia, Israel, Latin America, South Africa and the United States.

It can infect the whole plant, and the infected fruit surface is pink, yellow or yellow-green, and the lesion is sunken. Infected plants with new buds have strange yellow stripes under their stems, and their lateral branches turn green at the same time. The most obvious symptom on the leaves is the lack of green patches in the midvein or other vascular bundles, and occasional stripes on the diseased leaves. Sick leaves often distort.

Variety, environmental conditions, the number of viruses carried by the host tissue, and sick strains will all affect the symptoms. Some plants have no symptoms even if they carry a lot of viruses. Only a sharp drop in yield can indirectly indicate that plants may be infected with the virus. The transmission routes of ASBVd include: grafting transmission, which can be transmitted through grafted buds, scions, stem segments or veins of diseased trees. Under natural conditions, grafting transmission between roots will also occur. Symptoms appear 6 months to 2 years after transplantation. Mechanical transmission, ASBVd can be transmitted by blade cutting, but not by conventional friction inoculation. Symptoms usually occur 10 ~ 22 months after inoculation. The seed transmission rate is 5% ~ 100%. Pollen spreads, and the pollen carrying rate is% ~ 4%. Pollen from infected trees with symptoms or latent diseases can be infected.

Prevention and control methods: As ASBVd spreads through seeds, seedlings and pruning tools, no insect vectors are found, and many of them are hidden and toxic. Therefore, the most fundamental prevention and control measures are to strengthen quarantine, production and planting disease-free seedlings. The pruning tools can be treated with a mixed solution of 5% bleaching powder solution, 2%NaOH 1: 1 and 2% formalin or 6% H2O 2 to prevent the spread of diseases.

Common avocado diseases and their control methods: sunflower diseases

Bark, fruit and leaves are exposed to direct sunlight, and tissues are damaged by excessive drying and exposure. In the south and southwest of the tree, it was badly damaged. The damaged fruit appears pale yellow spots, the center turns black, brown or red, and then dies or withers. The damaged leaves first change color, and then form necrotic spots; The damaged shoots are cracked and discolored, and the surface becomes rough and purple. In severe cases, the bark of the trunk and branches falls off, and new tissues fade and die.

Fruit trees will lose their leaves, and when the fruit is directly exposed to the sun, or the fruit trees with shade in front often get sunburned. Shading leads to unhealthy root system or insufficient irrigation water, which is the main reason why these fruit trees are sensitive to sunlight.

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