Citrus is a tropical, subtropical evergreen tree (exceptionally), and it is warm and humid, but it is also afraid of heat. If the high-temperature abnormal weather of 30°C or above occurs during the flowering period of citrus, it will affect its normal flowering results. The earlier the emergence of high temperature, the greater the damage. During this period, due to the occurrence of abnormal weather caused by high-temperature weather, the phenomenon of loss of production is called citrus heat damage.
I. Causes of abnormal heat drop
1. The varieties and strains of different strains and abnormal fruit drop are different in abnormal fruit drop. The fruit-filling rates of 9-year-old Miyagawa Mandarin, Owari Satsuma Mandarin, Nanfeng Miju, Mandarin, and Taro were respectively 0, 0.8%, 4.1%, 4.8%, and 5.3%. The number of nuclear cultivars was severe, and the early fruit cultivars in Wenzhou mandarin were more severe than those in middle-late cultivars.
2. Tree age vigor and abnormal fruit drop The investigations on the 6-, 7-, and 8-year-old trees of O. satsuki were conducted. The fruit setting rates were 0, 0.8%, and 1.1%, respectively, indicating that the smaller the tree age, the more serious the fruit drop. At the same time, the investigation of the 9-year-old tree found that the tree-trending power, spring shoots, or tree vigor, flowering, no or less spring shoots are even more serious, and tree vigor and spring shoots The middle of the hair is lighter.
3. Fruiting branch type and abnormal fruit drop Under normal conditions, the fruit setting rate of leafy fruiting branches, especially leafy long fruiting branches, is higher, while the fruit setting rate of non-leafy fruiting branches is lower; but under abnormally hot weather, there are more fruitless branches with no degraded leaves ( 91% of the total number of fruit), short-fruited branches have less fruit (accounting for 9%), and the long-fruited fruit has fallen off.
4. The upper part of the canopy and the abnormal fruit-dropping crowns and the outside of the canopy have serious fruit drop (almost at the light), while the lower part and the inner pods have more fruit set.
5. Fertilizer spraying hormone and abnormal fruit drop Winter basal fertilizer was delayed until the end of December, and the spring fertilizer was too heavy, resulting in a large number of spring shoots, exacerbating contradictions in fruit shoots and aggravating fruit drop; the flowering and fruit-preserving measures were intensified when the hot weather in flowering season came. Abnormal drop.
6. Winter deciduous and abnormal fruit droppings Winter defoliation is severe, resulting in tree vigor degradation, affecting flower bud differentiation and flower quality, and severe flowering and falling.
7. Timely irrigation and abnormal fruit drop The high rate of fruit set in the trees that can be filled with water at high temperatures and droughts is high. During the high temperature period in May, 3 O. satsuki O. mandshurica were irrigated with 40 kg, 80 kg, and 120 kg of pig urine, respectively, resulting in the highest fruit setting rate of 120 kg, yielding 40 kg; irrigation of 80 kg was centered, yielding 30 kg; The lowest level of irrigation was 40 kg, and the strain produced 10 kg; while the adjacent unfilled trees had almost no yield.
8. Citrus production and abnormal fruit drop The heat damage caused by citrus in China resulted in abnormal fruit loss. The citrus production areas in the middle and lower reaches of the Yangtze River were the most severe, and occurred most frequently in the early spring of the spring and summer of May.
Second, heat damage warning
At present, the high-temperature early warning signals issued by the China Meteorological Observatory are divided into three levels, which are represented by yellow, orange, and red respectively, meaning that the 24-hour maximum temperature will rise above 36°C, above 37°C, and above 39°C. Citrus growers should pay attention to the high temperature forecast of the meteorological observatory and issue early warnings against the high temperatures that will occur, and take corresponding preventive measures to reduce the incidence of citrus heat damage.
Third, thermal damage prevention
1. Choose a site in the choice of citrus site, should consider the impact of high temperature as a major factor, as far as possible to avoid heat cultivation. For example, in a large-climate environment, where suitable local microclimates are selected, conservation forests can be set up to improve the ecological environment, and cultivation in rivers and rivers can also reduce heat damage.
2. Select a good variety should choose strong heat resistant varieties and rootstocks, such as the best selection of late-maturing varieties of sweet oranges, sweet oranges are best to choose nuclear varieties.
3. In order to fertilize the land for planting, the citrus planted on deep, loose and fertile soil in the soil shall have strong heat resistance; on the contrary, the heat resistance of the planted soil in the infertile soil shall be poor.
4. Strengthen the cultivation and management to strengthen the cultivation management can reduce the heat hazard of citrus, mainly including the following aspects of management:
1 Soil management. Focus on deepening the soil layer and increasing the content of organic matter in the soil. It is also possible to cover the trees. When the temperature is higher than 30°C, cover the unenclosed production trees. The implementation of the whole garden grass cultivation from March to September will also help reduce heat damage.
2 fertilizer management. One is to re-apply precipitating fertilizer. When the spring buds begin to germinate in early March, fertilizers based on available nitrogen fertilizers are re-applied to meet the needs of tree shoots, flowering and fruit setting. The second is to increase the application of phosphorus and potassium fertilizer, spraying the phosphorus and potassium fertilizers on the leaves frequently in the spring, which has obvious effect on preventing heat damage and reducing abnormal fruit drop.
3 moisture management. Watering in time to keep the soil moist can reduce heat damage, and the spray water is better than irrigation.
4 shoot management. The first is to protect the overwintering leaves. Put autumn shoots in place, and apply urea or diluted manure water after fruit harvesting to increase tree vigor and protect the leaves; spraying 2,4-D solution at a concentration of 10 mg/kg will also protect the leaves from the winter. The second is to reapply spring shoots and reduce the amount of new leaves. Spring shooters should be wiped early, re-wipe, and wipe: Early wipe is started from bud; re-wipe is based on the proportion of old and new leaves, wipe out excess spring shoots, and can also be erased after 70% of spring shoots The early summer shoots are used to make up for the insufficiency of the tree leaves; multiple wipes are applied to the shoots in batches, usually every 7 to 10 days until the second physiological fruiting end, and all late spring shoots after the late flowering period can also be erased. And early summer shoots, spring before the eradication of 30% to 50% of the spring tip, leaving 3 to 5 leaves left to pick up the spring tip.
5 Pest control. Do a good job in the prevention and control of buds, locusts, leaf nails, and anthrax, and protect the leaves and fruits.
5. Emergency measures
1 Spray the flower protection agent. Use synergistic liquefaction of cytokinin (BA) + gibberellin (GA, coated fruit type) or synergistic liquefied gibberellin + gibberellin (spray type). Coated fruit type (10 ml) per bottle (10 ml) plus 0.5-1 kg of water (0.6-0.75 kg of orange adult tree water, 0.75-1 kg of young trees, and 0.75-1 kg of water added to Wenzhou mandarin). Mix well and dilute the solution. . After 5 to 10 days after the citrus flower is cut, the whole fruit surface of the young fruit is coated with a brush pen dilute solution, and the fruit can be wetted. Generally, the amount of fruit is sufficient when the fruit is coated once. For some plants that grow weakly or are vegetatively prosperous and are prone to fruit drop, they can be applied again at the beginning of the second physiological fruit drop. Spray the bottle (10 ml) and add 10~15 kg of water and stir it well to make a dilution. When 70%~80% of the flowers are cut in the citrus, use the sprayer to spray the young fruit of the crown. Spray the fruit, leaves and Spray as little as possible on the new shoot. 10 to 25 days after the first spray, spray again. For varieties or plants that are susceptible to fruit drop, they can be sprayed for the third time 30 to 40 days after flowering, and rain within 12 hours after spraying. They should be fine. Spray 1 time. The use of a micro-sprayer (with a mosquito-killer or other miniature sprayer aimed at flowering, young fruit spray) is more effective. The micro-sprayer adds about 5 kg of water to each bottle. Pulps should be tested in small areas before spraying to ensure safety. The mandarin orange of Wenzhou can also be used as its special fruit preserver - Baogan Ling. Usage: Each package Polan Ling powder plus 50% to 70% alcohol or liquor 25 to 50 grams, stir dissolved, add water 25 kilograms spray canopy, spray the end of full flower spray for the first time, 15 to 25 days after heavy spray 1, Spray flowers and fruit are the main ingredients and can be moistened.
In addition, it is also possible to spray gibberellin 10 mg/kg + 0.4% to 0.5% potassium dihydrogen phosphate + 0.1% borax solution during flower buds; within 7 to 15 days after flowering, gibberellin 30 ~ 40 mg/kg + Cytokinin 800 times the liquid; the second physiological fruit spray 10 mg / kg 2,4-D + Lvbao 800 times to prevent the abnormal fruit drop in Wenzhou oranges. Paclobutrazol can also be used to protect the fruit, when the spring shoots 1.5 cm long when the spray growth inhibitor paclobutrazol (prescription effect is not ideal), 7 to 10 days before spraying again.
2 ring circumcision. From the early flowering stage to the late flowering stage, the primary fruit tree or the large branch of the Prunus mume tree is cut or girdled.
3 spray fungicide. The bactericide such as buprenorbuzine can be used to prevent mold infection before the rain, and it is also effective to shake off the residual flowers and raindrops after rain.
China leading manufacturers and suppliers of Active Pharmaceutical Ingredient, Mupirocin , Mupirocin Calcium, and we specialize in Sodium Fusidate, Fusidic Acid.
Active Pharmaceutical Ingredient, Mupirocin, Mupirocin Calcium, Fusidic Acid, Sodium Fusidate Manufacturer
Fuzhou Contay Biotechnology Co., Ltd , https://www.contaybio.com