Control Techniques of Early Non-disease Apple Defoliation

In the process of apple planting, non-disease factors can also lead to early defoliation. The prevention and control techniques are introduced as follows for fruit growers' reference.

I. early defoliation caused by insect pests

The main pests harmful to leaves are Spodoptera litura, leaf miner, boat caterpillar, beetle, pear net bug, red and white spider and so on. Leaf mites mainly suck leaf juice on both sides of leaf veins by piercing and sucking mouthparts. When the damaged leaves are serious, the leaves lose green, turn white and red on the front, and obvious white catkins can be seen on the back, and finally the leaves fall off. In the prevention of mites, it is necessary to grasp four key periods, namely, the dormant period, the spawning period, the egg incubation period, and the high temperature and humidity period. In the early stage of occurrence, 3000-fold solution of 20% Altair and 10% 6000-fold solution of mites can be used to kill female adult mites and mite eggs and hatch young mites; in the middle and later stage of major occurrence, 1.8% mites 10000 times solution, 1.8% insect mites light 8000 times solution, 200% triazotin 3000 times solution can be used to eliminate adult mites and nymphs in all growth stages. Most of the pests of Spodoptera litura and Caterpillar are larvae clustered on the back of the leaves to feed on the mesophyll or juice, causing damage to the leaves and leading to early shedding. It can be used for water agent kungfu, thiazuron 3, Wanling and pyrethroid pesticides for control.

Second, early defoliation caused by man-made or improper technology

The defoliation caused by artificial or improper technology mostly refers to the defoliation caused by the technical and operational mistakes of some fruit growers. For example, when administering medicine, randomly increase the concentration of the drug, and cause fallen leaves after the formation of drug damage; in the process of topdressing, excessive concentration and use of quick-acting chemical fertilizers (especially nitrogen fertilizer) form fertilizer damage and cause fallen leaves; again, when thinning flowers and fixing fruits in orchards, pulling branches and taking branches, the technology is not good enough to cause fallen leaves. The preventive measures are as follows: when administering the pesticide, the pesticide must be applied according to the effective concentration and the lowest effective dose of the pesticide; when topdressing, according to the tree age, tree potential, fruit amount, cultivation conditions, fertilizer types, etc., increase or decrease fertilizer as appropriate, do not apply too much fertilizer; when working in the orchard, be careful and standard operation, do not damage branches and leaves.

III. Early defoliation caused by adverse environment

1. Drought and waterlogging. In the hot summer day, when the temperature is more than 34 ℃, the soil moisture in the garden is quite low, which is far from enough to meet the needs of the trees. in this extremely dry condition, it often leads to the acceleration of cork, the imbalance of physiological regulation and serious self-thinning, and finally leads to the early fall of leaves. In addition, sudden torrential rain or continuous rainy days will make the orchard stagnant water and cause soil consolidation. In this environment, it is most likely to cause the physiological function of the root system to decline, the transport tissue is blocked, forcing the tree can not carry out normal physiological operation, resulting in leaf discoloration, atrophy, green dry or dry, resulting in early shedding. To this end, orchard water management should be done: timely irrigation during drought, quick drainage when waterlogging, skillful water control by watching the sky and trees.

two。 Poor lighting. In some orchards with poor light, the middle and lower branches and leaves can not see direct light for a long time, parasitic growth, most of them are in a state of ineffective consumption. The leaves were light green and thin in the early stage, and ethylene was produced and released in the later stage, which turned to egg yellow and matured prematurely. This symptom needs to be greatly reshaped, and measures such as dry lifting, head dropping and branch pulling should be taken to make the light transmittance of the orchard reach 35% to 40%, so that the leaves will not turn yellow and fall early.

3. Hailstorm. Hailstorms often occur after the beginning of summer every year. After the fruit trees were attacked by hail, the branches were cracked, the leaves were incomplete, and the organs and tissues were necrotic, so they could not perform normal physiological functions. The photosynthesis of injured leaves decreased sharply, and early defoliation occurred soon after a short interval. Rescue measures: first, immediately after the hail disaster, the whole garden was carefully sprayed with fungicides to strictly control the disease, followed by topdressing and foliar spraying to restore the tree as soon as possible; the second is to clean up the residual branches and leaves in the disease area to reduce the source of disease bacteria; the third is to install anti-hail nets in the orchard to reduce disasters.

4. Deficiency of elements. In recent years, in the application of base fertilizer in autumn, fruit farmers only pay attention to the use of farm fertilizer and a large number of element fertilizers, ignore the collocation of trace elements, and fail to achieve the purpose of formula fertilization, resulting in the lack of a certain trace element in the orchard. In the production, it was found that the flesh of the young leaves of iron-deficient fruit trees lost green and yellowed, and when the leaves were serious, they withered and fell off. Magnesium-deficient fruit trees, the leaves at the base of the new shoots gradually appeared light green patches, slowly turned yellowish brown, and fell after curling for a few days. For this reason, before fertilization, soil sampling test should be carried out, according to the test situation, fertilization scheme should be determined, formula fertilization should be popularized, and attention should be paid to the nutritional balance of nitrogen, phosphorus, potassium and various trace elements.