Prevention and treatment of harmful symptoms of common diseases of kiwifruit

Prevention and treatment of harmful symptoms of common diseases of kiwifruit

Fund projects: 2016 Tai'an Science and Technology Development Plan (2016NSOO57); Shandong key R & D Program (2017GNC10118).

1 canker disease

Kiwifruit canker is a bacterial disease caused by Pseudomonas clove pathogenic variety of kiwifruit (Pseudomonas syringae pv Actinidiae). At present, the disease has become a destructive disease restricting the development of kiwifruit industry. Kiwifruit canker has the characteristics of wide range of growth, rapid spread, strong pathogenicity and difficult to eradicate, which can cause large area tree death in a short time.

1.1 harmful symptoms

The disease can harm tree trunks, branches, shoots, leaves and other parts. After infection, the cortical tissue of the trunk or branch became soft and raised, and the diseased part cracked, and the milky mucus overflowed from the wounds, lenticels, bud eyes, leaf scars, branch bifurcations, etc., and then turned yellowish brown. In the host sore period, it was often mixed with sore fluid and showed reddish brown or reddish red, which was contagious. Phloem decay could be seen when the cortex was peeled off, the xylem was dark brown, the diseased tissue sunken and rotted like an ulcer, and in severe cases, the whole plant was infected. Tree body death After the young leaves of the twigs were infected, the young leaves curled and the buds wilted and could not open; the leaves first formed small red spots, the yellow halo of 2~5mm could be seen on the periphery, and then formed irregular or polygonal brown disease spots, which were consistent with the leaf surface in the later stage, but the color was dark, and the exudates were scaly when they were dry and dehydrated, and the damaged leaves were easy to fall off.

1.2 occurrence regularity

The pathogen overwintered mainly in the branch and vine disease tissue, and could also overwinter in the soil with the disease residue. Overflow of bacteria from the disease department in spring, through wind, rain, insects or in agricultural operations, spread through scissors, farm tools, etc., through stomata, water holes, lenticels, wounds (insect injury, frostbite, knife injury). After the pathogen invaded the cell tissue, after a period of reproduction, destroyed the transport tissue and mesophyll tissue, spilled bacterial pus for re-infection.

Low temperature and high humidity are beneficial to the disease. The disease will be aggravated by low temperature and rainy in early spring and long freezing injury in winter. When the ten-day average temperature in spring is 10-20 ℃, it is beneficial to the spread of the disease. The most suitable temperature for disease onset is 15 ℃. When the temperature exceeds 25 ℃, it stops expanding and no new disease spots appear. In the whole growth period of kiwifruit, the disease was more common in the spring bleeding period, and then became heavier. Except for the serious damage to the trunk, the incidence on the main branches and lateral branches increased rapidly, and the spread of the disease slowed down gradually after the flowering stage, and the disease spot basically stopped expanding with the increase of air temperature.

1.3 Prevention and control methods

① strengthened quarantine, did not transfer breeding materials from the disease area, and destroyed the diseased plants immediately. ② reduces the wound of tree and the infection of bacteria. ③ should strengthen the management of soil, fertilizer and water and cultivate strong trees. ④ disinfection scissors. After pruning the diseased tree, you can not use the same pair of scissors to prune the diseased tree. It should be strictly sterilized before use. Alcohol or fire can be used. When ⑤ occurs in spring, if reddish-brown bacteria are found to flow out, scrape off immediately. When scraping to the junction of the disease, the scraper needs to be sterilized and then scraped again. After shaving, smear with 50 times green copper, or smear with stone-sulfur mixture solution plus 72% agricultural streptomycin, the scraped diseased skin should be burned off and can not be left in the garden. ⑥ mastered three key control periods: after fruit harvest or before winter, after the Beginning of Spring to before sprouting, after sprouting to flowering stage. There are 95%CT powder, agricultural streptomycin, Shiduqing, copper hydroxide and so on. ⑦ cleans the garden thoroughly. After pruning in winter, the withered branches, leaves and fruits will be centrally treated or burned to reduce the spread of pathogens.

2 anthrax

Anthracnose is a fungal disease, which occurs in all producing areas, mainly harms leaves and fruits, and can also infect branches. It has been reported that the main pathogens causing kiwifruit anthracnose are Colletorichum gloeosporioides, C. acutatum, Glomerella cingulata and so on. Some domestic scholars believe that the pathogen of the disease is G. septospora, and the pathogen can only be caused by inoculation of kiwifruit stalks.

2.1 harmful symptoms

The injured leaves often appear grayish-brown disease spots from the edge, showing waterlogging at the beginning, obvious at the junction of the disease and health, and gradually turning to brown irregular spots; in the later stage, the disease spots become gray-white in the middle, and the edges are dark brown, on which there are many small black spots (that is, the conidium disk or ascomycete shell of the pathogen). Some disease spots break into holes in the middle, the leaf edge curls slightly to the back of the leaf, and the leaves rot and fall off when it is wet and rainy. After the damage of the fruit, a round and brown disease spot was formed, and the surface was slightly sunken, and there were small grain spots in the later stage of the disease spot, and if the weather was wet, it would overflow pink mucus; after the branches and vines were damaged, they began to form light brown spots, which were brown around the disease spot and expanded into an oval shape in the later stage.

2.2 occurrence regularity

The pathogen overwintered with mycelium and conidia disk in diseased body, bud scale, axillary bud and so on. In the next spring, the pathogen produced conidia, which was transmitted by wind, Rain Water and insects, and invaded from stomata, wounds or epidermis, with latent infection. Kiwifruit orchards with high temperature and humidity are heavy and easy to mix with other diseases.

2.3 Prevention and control methods

① strengthens cultivation management. Reasonable pruning, application of organic fertilizer to enhance the tree potential. ② is combined with winter pruning to remove diseased branches and stiff fruits and remove overwintering pathogens. ③ chemical control, mainly prevention, optional agents are: Bordeaux solution, 70% Dysen zinc wettable powder, 50% carbendazim wettable powder, 30% difenoconazole suspension, etc., spray once every 10 to 15 days, even 2 times for 3 times, can prevent the occurrence and spread of the disease.

3 Brown spot

Brown spot is an important leaf disease of kiwifruit. It has been reported that Alternaria Alternaria alternate (Fr.: Fr.) Keissler is the pathogen causing brown spot of Actinidia chinensis.

3.1 harmful symptoms

It mainly harms leaves and branches, and sometimes the surface of fruit. The disease spot mainly originates from the leaf margin, but also has the leaf surface. At the initial stage, it showed a small green spot in the shape of water stains, and then expanded along the leaf margin or inward, forming irregular brown spots. Under the condition of heavy rain and high humidity, the disease develops rapidly, the disease spot changes from brown to black, and the boundary between disease and health is obvious. In a normal climate, the spot is dark brown around, brown to light brown in the center, and there are many small black dots scattered or densely produced on it, that is, the conidium of the pathogen. Under high temperature, the damaged leaves curled to the leaf surface, easy to break, and dried up and fell off in the later stage. The disease spot in the middle of the leaf surface is obviously smaller than that at the leaf edge, and the disease spot passes through the back of the leaf, yellow and brown.

3.2 occurrence regularity

The pathogen overwintered in the sick and disabled body in the form of conidia or mycelium, and the following spring spattered on the tender leaves for primary infection and multiple re-infection. In general, the disease begins from May to June, and enters the peak period from July to August. If it is rainy in September, the disease will be serious. High temperature and humidity are conducive to the disease.

3.3 Prevention and control methods

① cleans the garden thoroughly in winter. The pruned vines and fallen leaves will be cleaned out of the garden and burned; turn the orchard topsoil 10~15cm, so that the soil surface disease residual leaves and scattered bacteria buried in the soil, reducing the overwintering pathogens. ② should pay attention to shaping and pruning to make the orchard ventilated and transparent. Chemical control of ③ is carried out at the initial stage of the disease, and the optional agents are 1 ∶ l ∶ 100Bordeaux solution, 80% mancozeb wettable powder 1000 times, 50% methyl thiophanate or 70% methyl thiophanate 1000 times, etc., spraying once every 10 days for 3 times, can also control the occurrence and spread of the disease; after clearing the garden, 5 °6 °Be stone sulfur mixture can be used to kill bacteria and mites on vines.

4 gray mold

Botrytis cinerea mainly occurs in the flowering stage, young fruit stage and storage period of rhesus monkey peach. The disease is caused by Botrytis cinerea (Botrytis cinerea persoon). The pathogen is Sclerotinia cinerea (Botryotinia fuckeliana).

4.1 harmful symptoms

It mainly harms flowers, leaves and fruits. After being infected with the disease, the flowers turn brown and rot and fall off, and a large number of gray mildew layers are formed on the surface. At the initial stage of infection of the young fruit, water-stained spots were formed, then extended to the whole fruit, and gray-white mildew appeared on the diseased pericarp when the humidity was high. After the infected flowers fall on the leaves, the leaves produce white to yellowish brown disease spots, and gray-white mildew often appears when the humidity is high (that is, conidiophores and conidia of the pathogen). The fruit in the early growth stage is relatively resistant to disease, and the rot in the field is not common, but the infected fruit will quickly get sick in the cold storage and infect other fruits.

4.2 occurrence regularity

The pathogen overwinters as mycelia on diseased parts or decaying remains or in the form of sclerotia in the soil. Spores were produced under suitable conditions and spread by airflow and Rain Water sputtering. The high incidence period of Botrytis cinerea is from budding stage to flowering stage of kiwifruit. The pathogen could grow normally in 5-30 ℃, and the optimum growth temperature was about 20 ℃. Persistent high humidity, lack of sunlight and poor ventilation are easy to occur; moisture retention time is long and the disease is serious.

4.3 Prevention and control methods

① strengthens the management of soil, fertilizer and water and enhances the disease resistance of trees. ② pays attention to orchard drainage to prevent stagnant water in the orchard. ③ pruning properly, remove the diseased fruit in time, and take it out of the field and buried deeply, so as to keep the garden well ventilated and transparent. ④ grasps the key control period before flowering, and the optional agents are carbendazim wettable powder 800x, chlorothalonil wettable powder 600x, ethylene sclerotiorum wettable powder 1000 times, 50% isobarbamide wettable powder 800x 1000 times, and so on. Pay attention to the alternate use of medicine. Fruit injury should be avoided and reduced when picking fruit with ⑤.

5 Sclerotinia disease

The pathogen of Sclerotinia sclerotiorum is Sclerotinia sclerotiorum Sclerotinia sclerotiorum (Lib.) De Bary, can parasitize rape, eggplant, tomato, lettuce, pepper, potato, clover and other more than 300 kinds of plants.

5.1 harmful symptoms

It often harms flowers and fruits. The male flower suffers from water stains at first, then softens, then decays in clusters and shrinks into brown clumps; the female flower suffers, and the buds turn brown, wither and cannot bloom. Under rainy conditions, the disease grows white and mildew. The fruit was damaged, the initial stage showed water-stained chlorotic patches, the disease was sunken, and gradually turned to soft rot. The fruits with serious disease in the field generally fall off successively, and a few fruits are stiff due to pulp decay, peel rupture, juice overflow and shrinkage, and irregular black sclerotia grains are produced on the skin surface of the diseased fruit in the later stage. Diseased fruit is not resistant to storage and transportation and is perishable.

5.2 occurrence regularity

The mycelia multiply in large numbers and form sclerotia in the diseased fruit, and the sclerotia overwinters in the soil with the disease residue falling to the ground. The sclerotia of kiwifruit germinated at the beginning of flowering in the following spring, produced ascospores and ejected ascospores, which invaded the flower organs of kiwifruit by wind and rain and caused the first infection. A small number of ungerminated sclerotia in the soil can continue to germinate, infect growing fruits and cause fruit rot. The disease occurs rapidly when the temperature reaches 20-24 ℃ and the air relative humidity is 85%-90%. If the spring is warm and rainy, which is conducive to sclerotia germination and produce more ascospores, the disease will be serious.

5.3 Prevention and control methods

The pathogen was completely eliminated by ①. Remove the diseased fruit at any time and take it out of the orchard for deep burial; after fertilization in autumn, the topsoil 10~15cm was buried so that the soil surface sclerotia could not germinate and infect. Chemical control of ②. Grasp the three control periods before flowering, florescence and young fruit stage, the optional agents are 50% ethylene sclerotiorum wettable powder 1000 times, 40% sclerotia net wettable powder 1000 times, 70% methyl topiramate wettable powder 1000-1500 times, 50% Sukeling wettable powder 1000 times, and so on.