Early defoliation of apples is a general term for the early detachment of leaves when apple trees do not reach normal leaves. In response to this symptom and regularity, the scientific solution for the selection of pesticides is as follows: Lighting Switch,H-Series Light Switch ,Light Switch Rocker Switch Co,.Ltd , http://www.onbswitch.net
I. Pathogenesis The pathogens of apple brown spot and spotted leaf disease are overwinter in the diseased leaves, branches or bud scales by mycelium or conidia discs. After the apple blossoms, the overwintering pathogens germinate with the rise of temperature, and then spread by rainwater to produce a large number of conidia, firstly infecting the new leaves; there are two peaks of infection in one year: the first time in late April to June In the first ten days, especially the injured leaves within 20 days of the exhibition leaves are most susceptible to infection; after the infection, the symptoms do not enter the incubation period, and the time is ripe (about the beginning of July), and small lesions and disease centers appear on the leaves; the second time In September, the bacteria appeared to infect again. At the early stage of the disease, brown spots appeared on the leaves, and there were purple-red halos around them. In the later stage, several lesions were connected, and the yellow leaves of the leaves fell off in advance, forming early leaves.
II. Etiology reason Apple early defoliation caused a lot of major infectious disease hazards leaf spot and leaf spot, as well as spider mites and gold miner pattern and other pests. Second, the management is extensive, and the pests and diseases are seriously endangered; the Qingyuan is not thorough, and the diseased branches and leaves carry a large number of pathogens to survive the winter. Third, the orchard is closed, and the ventilation and light transmission conditions are poor; the high temperature and high humidity in summer are conducive to the expansion and spread of the bacteria. Fourth, the tree is weak, partial fertilizer, lack of organic fertilizer; can not be fertilized according to the growth law of fruit trees, resulting in poor disease resistance. Fifth, the stripping (cutting) is too heavy, especially for trees that have been knives for years. Early defoliation is most evident in these trees. Sixth, the prevention and treatment time is too late. Most of the fruit farmers see no diseased leaves in the field, and they will not prevent or delay the prevention and control, neglecting the incubation period of the bacteria. The result is that the medicine spray is not used up; then the drug variety is not right, and blind prevention occurs. The phenomenon.
III. Comprehensive control measures 1. Strengthen the management of soil and fertilizer in orchard, scientifically pruning, reasonable load, enhance tree potential, and improve the disease resistance of fruit trees; re-applying organic fertilizer and increasing phosphorus and potassium fertilizer are the fundamental measures to reduce the occurrence of diseases.
2. Renovate the closed orchard and promote thinning; the closed orchard should be thinned. Generally, the orchard should be remodeled. No matter what kind of tree shape is used, it must be “ventilated and transparent, smooth between rows, and the branches are not handed over and convenient for operationâ€. Requirements.
3. Qingyuan: Combine the winter shears to remove the diseased insects on the trees, clean them together with the fallen leaves on the ground, and focus on destroying the pathogens that eliminate wintering.
4. Chemical control: Since early defoliation has an incubation period, the chemical control should reflect an "early" word; three key prevention and treatment periods should be seized throughout the year; the first is before germination (mid-March), spraying 5 degrees The sulphur mixture requires the tree, the trunk and the ground to be sprayed together to eliminate the overwintering pathogen. For the second time, 7 to 10 days after flowering, a therapeutic fungicide such as 43% good gram 5000 times, or 50% Pu Hai 1500 times, or 50% methyl thiophanate 1000 times solution is used. For the third time, before the bagging, use the bactericidal agent for the second time, and add insecticide and calcium supplement. After bagging, a protective fungicide such as 50% Antaisheng 800 times solution, or 1% polymycin 800 times solution, or 12.5% ​​diniconazole 800 times solution is used. In the prevention and treatment of pesticides after flowering, pay attention to the prevention and treatment from May to August. After each spraying, the interval is 12 to 15 days, pay attention to the rotation of medication; in the rainy June to August, it is recommended to use 1 or 2 times of Bordeaux mixture; The number of prevention and control times is controlled at 6 to 7 times.