Root disease. With the vigorous development of jujube trees in Xinjiang, a large number of jujube seedlings have been introduced from the Mainland, and the disease has become increasingly serious in southern Xinjiang.
1 Distribution and Hazards
The disease is distributed throughout the country, with occurrence of stalk rot in jujube trees in Hebei, Henan, Shandong, Shaanxi, Xinjiang, and Zhejiang provinces. The disease mainly affects jujube seedlings and saplings, and can cause serious deaths of seedlings and young trees as a whole.
2 symptoms
When the seedlings began to develop, a water-stained dark brown spot appeared on the base of the stems, which immediately surrounded the whole stems and expanded rapidly. At this time, the leaves turned yellow, withered, and gradually withered. The base of the victim's stem is subsidence, and the cortex is tightly attached to the stem. It curls up and is not easily peeled off. In the late stage of the disease, many black spots (the conidia of pathogens) are produced in the diseased part, and there are gray mold piles (that is, the conidia of pathogens) when it is wet.
After the sapling became sick, the symptoms were the same as those of the seedlings, but the lesions appeared to be slower than the seedlings in the first round around the stems. Most of the roots of seedlings and saplings that are susceptible to light do not die, sprouting sprouts from the root neck.
3 Pathogens
The pathogen of stalk rot in jujube tree is a bacterium belonging to the genus Deuteromycopsis in the fungus. It is a kind of soil habitual bacteria commonly found in the tropical and subtropical regions of the world. Conidiophores are nearly spherical or oblate spheroids, with diameters of 89 to 275 microns and X98 to 225 microns. They are buried under the epidermis of the host, and the posterior orifices are exposed through the epidermis. Conidia are oblong or ovate, colorless, and have a size of 16 to 32 microns X 5 to 10 microns. Its host range is very wide, in addition to harming jujube trees, it also harms a variety of seedlings, such as ginkgo, camphor, cedar, fir, metasequoia, larch, pine, pine, pine, cypress, arborvitae pine, The seedlings of coniferous broad-leaved species such as cypress, oak, black sorghum, tung tree, and eucommia ulmoides endanger various crops and vegetables such as sweet potatoes, hemp, cotton, sunflower, beans, tobacco, peanuts, corn, and sorghum. On sesame and jute, as on jujube trees, conidia are easily formed. Sclerotia are most easily formed on a variety of coniferous hardwood seedlings and many crops. Sclerotia black, smooth surface, nearly round or flat spherical, size affected by nutritional conditions, the general diameter of 5 to 100 microns.
The bacteria have strict requirements for the pH value of the soil. The pH value can be grown from 4 to 9 and the optimum temperature for indoor culture is 30-32°C.
4 Disease cycle and epidemic
The jujube stem rot pathogens mainly used mycelia, sclerotia, or conidia for wintering in diseased areas and soil, becoming a source of infestation in early winter. Use wind and rain, irrigation water to spread. Under appropriate conditions, it invades the host from the wound and re-infects it.
Seedlings of wild jujube and jujube seedlings were excavated and sprouted to 3 to 10 cm and 3 to 10 leaves.
At the time (usually at the beginning of May), the green main stem and leaves appear pale yellow, then pale, withered and died. However, pale leaves do not fall. Digging the roots to observe the roots, it can be clearly seen that the main stem in the diseased soil layer dark brown, cortex rot, the main stem xylem and marrow have been necrosis, due to normal transmission of tissue disruption, seedlings withered, and some root systems have also rot. The old roots of the nursery seedlings, which are connected to the main stem, have necrotic dark spots and the cortex rots. There are many small black sclerotia, which have been confirmed by inoculation and invaded the existing xylem that has not changed color. Jujube trees mostly appear on 1-2 years old seedlings.
The disease is a kind of weak parasite. Usually in the soil to live in rot, with sclerotia and mycelium in the disease residues and wintering in the soil. When the temperature is high in the late spring and the external conditions are suitable, the host is infested. Hi-temperature, high-humidity environment. Southern Xinjiang jujube area, on the jujube tree in early May onset, in mid-June is the epidemic period, stop the onset in early July.
The occurrence of diseases is closely related to the host state and environmental conditions. High temperatures and rain are conducive to disease. Especially at high temperatures, if there is continuous rain for a few days, the weather is hot and the air humidity is high, it often induces a disease or epidemic. The reason why the disease is particularly serious in southern China, mainly due to high temperature and humidity. However, in recent years, with the changes in the atmospheric environment, the north has become warmer and the disease has become serious. Low-lying terrain, soil is too wet, or long-term water irrigation canals, and the jujube trees that are too moist in the soil are conducive to the breeding and infestation of pathogens, and they are unfavorable to the growth of jujube trees, and therefore the incidence is heavier. Flooding is also conducive to disease. High temperatures and droughts are also conducive to the occurrence of diseases. The high temperature and the sun in summer and autumn increase the soil temperature. The damage to the base of seedling stems due to the high soil temperature creates the conditions for the invading bacteria.
Seedling stalk rot occurs in the seedlings from 5 to 7 months of actual season and the seedlings returning to nursery and saplings planted for 1-2 years.
Rehearsal jujube garden due to small temperature difference between the surface, the temperature is lower, the incidence of jujube stem rot is light, the desert temperature and the date of the jujube garden are large, the temperature is high, and the stalk rot of the jujube tree is heavy. Jujube stalk rot occurs mostly on the surface of the main stem at 1-3 cm, and the lesion is 1-2 cm long. Desert stalk rot in jujube orchard in desert drip irrigation is severe. It may be related to black endothermic and drip irrigation, high local temperature, and may be related to mulching (high temperature, high humidity). The specific reasons need further study.
5 methods of prevention and control
5.1 Increase the use of high-quality organic fertilizer to promote the host's robust growth and increase resistance to disease. The use of manure as a base fertilizer, 3000-5000 kg per 667 square meters, can greatly reduce the disease rate. At the same time, it may affect the changes of the antagonistic microbial population in the soil and inhibit the growth and spread of germs.
5.2 Timely drainage and irrigation. For the low-lying and poorly-drained plots, it is necessary to strengthen the trenching and drainage work. During the hot and dry summer season, irrigation should be conducted in time to reduce the surface temperature and prevent the surface of the stem from burning at high temperatures. This will increase the host's viability, increase disease resistance, and reduce the incidence.
5.3 Root application. With 40% pentachloronitrobenzene wettable powder (75%) plus 50% carbendazim wettable powder (3:1 mixture ratio), and then add 0.3 grams of ground Health (Henan Agricultural University Huafeng Science and Technology Development Co., Ltd. Production) 500 times liquid irrigate root, or smear on stem base, can prevent disease and promote root growth, improve disease resistance. Or use 40% pentachloronitrobenzene wettable powder (75%) plus black vinegar (ferrous sulfate) (25%) plus ground drop 0.3 g 500 times liquid to root.
5.4 soil disinfection. In the germination stage of jujube, the seedbed was generally sprayed with 1:1:200 Bordeaux mixture, or 50% of WP wettable powder 800-1000 times was used to sterilize the soil.
5.5 to strengthen management, drip irrigation pipe and drip tape placed 8-10 cm away from the base of the jujube tree stem, covering the mulch in the base of the jujube tree dig a hole with a diameter of 20 cm, cut away lesions, reduce pathogens.
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