Kiwifruit is a kind of emerging fruit with good economic benefits and remarkable ecological benefits. It has developed rapidly in our province in recent years. However, with large-scale orchards entering the fruiting period one after another, kiwifruit yellowing disease occurs in varying degrees in the planting areas, especially in wetlands with high groundwater levels. The incidence rate is relatively high, and the incidence of diseased plants accounts for 10 of the total number of cultivated plants. About %, the incidence rate of serious field plots is as high as 20% to 30%, and some new gardens have 1 to 2 years old seedlings, which poses a serious threat to the sustained and healthy development of the kiwifruit industry in our province. In order to solve this problem, the author of the China Agriculture and Forestry Network investigated and summarized the main causes of yellowing caused by current production and put forward specific prevention and control measures.
First, the symptoms
The main damage leaves, diseased leaves in addition to light green veins, the rest are yellow chlorosis, small leaves, weak tree vigor, severe leaves pale, the outer edge curled to death. After the fruit is damaged, the skin becomes yellow, the flesh is cut white, and the value of food is lost. The long-term disease will also cause the trunk to die.
Second, the main cause of the disease
1. The alkaline pH of the soil has a great influence on the content of available iron. At pH 5.5-6.5, the kiwifruit is most effective in absorbing iron. After the pH is higher than this range, it gradually decreases. The pH value of the soil in the north foot of the Qinling Mountain is close to 7.0, and the effective content of iron can still meet the kiwifruit growth results. However, from this region to the north, the pH value of the soil gradually increases, especially the pH value of the Fenhe Beach is relatively high, which can reach about 8.0. In the alkaline soil layer, free divalent iron ions are easily oxidized to trivalent iron ions and thus they cannot be absorbed and used by the kiwifruit root system. In addition, the kiwifruit is a fleshy root, and the root distribution layer is relatively shallow, making it easier. Iron deficiency yellowing occurs. Therefore, the incidence of yellowing disease along the Weihe Beach and National Highway 310 is relatively high.
2. Irrational farming
1 Partial application of nitrogenous fertilizers can cause misalignment of many trace elements such as zinc, copper, magnesium, and manganese in the soil. Antagonism between the elements can occur, causing yellowing disease.
2 The high groundwater level, excessive watering, excessive flooding, and flooding in low-lying land can easily cause poor air permeability, cause diseases in the roots of kiwifruit trees, and cause disturbances in physiological metabolism of trees and yellowing. Some growers understand the characteristics of the drought-tolerant kiwifruit trees. The garden surface is watered with a little dryness, resulting in excessive irrigation times. In fact, the kiwifruit's ability to bear crickets is poorer than that of drought tolerance. Frequent irrigation and soil compaction caused by irrigation make yam yamanashi pests and insect pests prevent the lack of oxygen in the soil, and the microorganisms in the soil produce ethanol during the process of anoxic respiration. Toxic substances cause serious damage to the root system, causing tree growth and yellowing.
3 The soil in the garden soil is shallow, with severe drought and consolidation, and poor permeability.
4 When the garden was built, the seedlings were planted too deep and the soil between the rhizospheres was hard, resulting in lack of oxygen in the root system, poor breathing, and yellowing of the trees.
5 If the orchard is deeply turned and fertilized improperly, causing root damage, or using organic manure without ripening, it will cause damage to the underground pests and it will also induce yellowing disease.
3. Too much fruiting quantity Many fruit growers blindly pursued high yields and abused fruit swelling agents, resulting in serious excess of results, which was the most common cause of the occurrence of yellowing disease. Because the bulking agent does not increase nutrition, it only changes the proportion of nutrients and causes the tree to weaken after use, causing yellowing and other deficiency diseases to occur. In the investigation, the author found that some of the orchards had normal leaf growth in the early stages, but the newly emerged leaves appeared yellowish symptoms shortly after the use of the bulking agent; at the same time, it was also found that the female plants with fewer male plants and less fruit had less yellowing and lighter degrees.
4. Root diseases Kiwifruit root diseases such as root rot and root knot nematode diseases interfere with and destroy the function of roots to absorb and synthesize and use various mineral nutrient elements in the soil. Therefore, physiological diseases are caused by pathological diseases in the roots. Symptoms cause yellowing of the leaves on the trees.
Third, prevention and control measures
1. Scientific Site Selection The new garden of Jianyuan must be selected in the optimal ecological zone with the best ecological conditions. The suitable soil pH is between 5.5 and 7.5, not more than 7.5. This is the fundamental way to prevent yellowing. As far as possible, choose sandy soil blocks with deep soil, fertile soil, and good permeability. The organic content of plough layer soil is above 1.5%, and the groundwater level is below 1 meter. It is not advisable to build parks in the floodplain areas with high groundwater levels and prone to water accumulation. Seedlings should not be planted too deep. It is advisable to keep the roots of the seedlings and the ground at the same level after irrigation. However, it should not be too shallow to avoid watering the seedlings and affecting the landscape and growth.
2. Strictly control the production of products without unilaterally pursuing high yields. Do not use fruit bulking agents. The yield per mu should be controlled at 2000 to 2500 kg in the fruit period to prevent excessive loading and maintain strong tree vigor.
3. Implement balanced fertilization
1 Vigorously promote balanced fertilization techniques so that nitrogen, phosphorus and potassium can be combined, and a large number of elements can be combined with trace elements.
2 Try to use physiological acidic fertilizers or neutral fertilizers such as ammonium sulfate, potassium sulfate, superphosphate, potassium dihydrogen phosphate, urea, ammonium phosphate, etc. Do not use physiological alkaline fertilizers.
3 increase organic fertilizer, increase soil organic matter content, promote the formation of soil aggregate structure. In the fruiting period, the tree grows 4000-5000 kg of organic fertilizer per acre in autumn, and appropriate amount of trace element fertilizer such as ferrous sulfate is added to increase the effective iron content in the soil. The farmyard fertilizer should be decomposed and should not be too deep when fertilized. Green manure such as clover is planted and covered in the garden after being castrated, and then turned into the soil after decomposing.
4. Reasonably irrigated kiwifruit trees in orchards are both hi and afraid of water. When irrigation, we must strictly control the amount of irrigation, change the flood irrigation into small water irrigation or separate row irrigation, to avoid blind irrigation, excessive irrigation, reduce the number of irrigation, beware of garden Water inside. The moist leaves on the early morning usually do not need watering. For conditional orchards, furrow irrigation, drip irrigation or infiltration can be used.
5. Timely cultivating loose soil After irrigating or under heavy rain, loosen the soil when it is suitable, break the soil compaction, keep the soil breathable, and ensure that the root system has a strong vitality. If the soil in the garden is heavy, it is necessary to combine deep plowing with more organic fertilizers, and soil conditioners may be used to “treat the soil deeper†to treat the soil.
6. Symptomatic treatment of medicines For plants that have already developed yellowing disease, they can be treated with foliar spray of kiwifruit special liquid or hanging on the trunk with hanging bottles. According to the author's production practices over the past few years, how to determine the apple harvest time on the foliage spray Tsuien 1 800 to 1000 times the liquid effect is particularly evident. In the spring, when the shoot length reaches 15 cm, the tree body can be sprayed. After 5 pm on the sunny day, the effect is better. Each spraying interval is 7 days, and the spray is repeated 3 times. For the yellowing plants induced by pathological root diseases, on the basis of cutting off the diseased roots and scraping off the diseased skin, use 5% sputum poisonous liquid 200 to 300 times liquid or 50% carbendazim wettable powder 500 to 600 times liquid, alternating Use, Irrigate 2 or 3 times. The root-knot nematode-induced deficiency of the yellowing tree, can use 48% chlorpyrifos EC 1000 times spray rhizosphere soil, kill root-knot nematodes, combined with the removal of diseased fibrous roots, and promote the restoration of physiological functions of roots as soon as possible.
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