In recent years, the early deciduous phenomenon of apple in Hengshui City was serious, which seriously affected the fruit yield, quality, and the formation and differentiation of flower buds, resulting in declining tree growth year after year, worsening of trunk diseases, and even dead trees. To this end, we conducted a comprehensive survey and analysis of the apple orchards in Hengshui District. We will now summarize our analysis of the survey results.
First, early defoliation caused by disease infection
Foliage caused by leaf diseases is the most common and most serious form of early apple defoliation. The diseases that cause early defoliation in apple are mainly brown spot, spotted deciduous disease and other diseases. Sometimes the leaves are full of many lesions, but not all are yellowing off. The disease occurs sooner or later and has a heavy weight. It is closely related to the morning and evening of the rainy season and the amount of rainfall. The rainy season comes early, and rain and rain are the main sources of its serious occurrence. In addition, the majority of fruit growers attach importance to the prevention and control of pests and diseases before bagging, neglect the prevention and control of pests after bagging, and cause serious early defoliation, severely affect tree vigor, affect the formation and differentiation of flower buds, and then affect the output and quality of the year.
Prevention and control measures: First, clear the garden work, remove fallen leaves, and reduce the source of the disease. The second is to strengthen the comprehensive management of orchards, increase phosphorus and potash fertilizers, increase tree vigor, and increase disease resistance. The third is chemical control. After bagging apples, it is necessary to focus on protecting the leaves and continue to strengthen the control of pests and diseases. Starting in early June, the control of brown spot is mainly for Red Fuji and Jura, spraying once every half month or so, paying attention to rain, after catching rain, the agent is generally 1:2:200 Bordeaux fluid. In the rainy weather, thiophanate-methyl, carbendazim, and other systemic agents may be used to prevent and control spraying in the rain. Red stars, new red stars, gold crowns and other varieties should be sprayed once a half of 1.5% polymycin or acetaminophen. If there is more rain, the interval between sprays or spraying should be reduced.
Second, early defoliation caused by insect pests
The pests that cause defoliation in apple trees include: spider mites, two-leafhoppers, leafminers, pears, and other insects. The cricket sucks the leaf juice with a sucking mouthpart, resulting in a chlorosis of the leaf, whitening, reddening, and finally shedding of the leaf.
Measures to control mites: The winter is the basis of prevention, treatment after flowering is a critical control point sheet damage, protection and utilization of natural enemies. Over the winter dormancy scrapes old bark to eliminate overwintering, after flowering and before wheat harvest, it is the critical period of medication. The agent for preventing and controlling spider mites is schizophylline, and avermectin and triazotin also have good control effects on red and white spiders. Most of the caterpillar pests are larvae that feed on the back of the leaves to feed on the leaves or juice, leading to premature shedding. They should spray out urea urea 1500 times at the peak of adult emergence and have a good control effect.
Third, the early fall leaves caused by environmental impact
1. Tree malnutrition. Apple blossoms and fruit set consume large amounts of nutrients. The fruits are in a period of rapid increase until June and July. If the trees are not well stocked with nutrients and they are not supplemented with fertilizers in time, they will cause nutrient breakage and cause the leaves to fall off. Therefore, in late May to early June, timely recovery of fertilizer should be used to make up for the nutritional loss caused by flowering and fruit setting, and timely watering after fertilization.
2. Drought and disaster relief. Severely drought-defoliated deciduous leaves begin to fall off from the base leaves and inner leaves. As the drought continues to become more severe, the fallen leaves are golden yellow, and no spots, watering or leaves immediately after the rain stopped. Stagnant water into deciduous leaf, mostly in the viscous soil or low-lying area, the area of ​​water, poor soil ventilation, root suffocation and loss of absorption capacity, sudden emergence of serious defoliation. This kind of deciduous chlorosis turns yellow and there is no disease spot. Before the rainy season comes, we should do a good job of drainage system and eliminate excess water in time.
3. The trees are closed, the long-term illumination is insufficient in the internal condyle, and the leaves are thin and yellow and fall off. This situation should focus on summer pruning, timely cutting off dense branches, leggy branches, competing upright branches, overlapping branches, improve lighting, improve photosynthesis, so that the orchard canopy light transmittance of more than 30%.
4. The lack of disease. If the soil is iron-deficient, the young leaves of the fruit tree will lose their greenness and yellow, and the leaves will fall off and fall off when they are serious. Therefore, soil testing and formula fertilization should be carried out to achieve the balance of nitrogen, phosphorus, potassium and various trace elements.
Fourth, the early fall caused by human factors
Arbitrarily increase the concentration of medication, resulting in phytotoxicity; in the fertilization process, over-application of fertilizers, resulting in fertilizer damage, causing early defoliation. Preventive measures: When fighting drugs, be sure to use the effective concentration of the pesticide instructions, and do not buy cheaper quality pesticides. When top dressing, it is necessary to determine the amount of fertilizer depending on the age, vigor, and amount of fruit, and do not use excessive fertilizer.
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