Walnut is one of the four major nuts in China, and it is also the category that many growers choose to grow. Have you ever encountered blackened walnut skin? Is this a disease or a pest? The following small series will give you detailed answers.
1 Cause
According to the continuous investigation of multiple walnut gardens for many years, it is known that there are two direct causes of this phenomenon: one is pests, the other is diseases, and often it is mixed and harmful. The specific reasons are as follows.
(1) The harm of walnut limb moth. In mid-June of each year, when the wheat is matured and harvested, the newly hatched larvae will be drilled into the walnut skin to feed. The early damage can cause the black skin of the walnut to fall off, and the walnut black skin will be dried up later. July is the most serious hazard.
(2) The harm of walnut fruit weevil. Every year in mid-May, the larvae penetrate into the walnut skin and harm the nuts, causing the fruit to become black and fall off.
(3) The harm of walnut anthracnose. The peak incidence period is from June to August each year. After the walnut is damaged, round brown or dark brown lesions can appear on the peel, and the lesion is centrally concave and has small black spots. After severe occurrence, the lesions are contiguous, causing the fruit to become black and rot, causing fruit drop after early damage. In the orchard with heavy rainfall, high humidity, high temperature, weak tree and poor ventilation, the disease occurs early and severe. The germs spread by wind and rain and insects, and are easily invaded from wounds and pests.
(4) The harm of walnut black spot disease. The disease is a bacterial disease. After the fruit is damaged, it will produce small spots of brown water stains, which will expand into irregular shapes without obvious edges. When severe, the fruit will turn black and rot, and the nuts will dry up.
2 Preventive measures
(1) Before germination, plow the land under the tree and eliminate the wintering walnuts.
(2) Before germination, evenly spray 3 to 5 waves of sulphur sulphur mixture to prevent diseases such as walnut anthracnose and walnut black spot.
(3) At the beginning of May, the whole garden sprayed 2.5% beta-cypermethrin EC 2000 times solution and 75% chlorothalonil wettable powder 600 times solution to prevent walnut pests and walnut diseases.
(4) In late May, the whole garden sprayed half of the Bordeaux mixture to prevent diseases such as walnut anthracnose and walnut black spot.
(5) In mid-June, when the wheat was opened, the whole garden was sprayed with 25% chlorpyrifos No. 3 suspension agent 1000 times liquid and bacteriostatic WP powder. Prevention and treatment of walnut limb moth and walnut anthracnose, walnut black spot.
(6) In the middle of July, the whole plant is sprayed with methyl thiophanate WP powder for prevention and treatment. Generally, it can be sprayed once every 10 days, which can effectively prevent walnut diseases.
(7) After harvesting the walnuts, clean the diseased leaves, diseased fruits, and diseased branches in time, and burn and destroy the overwintering bacteria and pests.
(8) After the walnuts are harvested, the whole garden is spread with organic fertilizer, phosphorus and potassium fertilizer. After fertilization, turn soil and water, promote root growth and development, enhance tree potential, and improve disease resistance.
(9) Anti-sunburn during high temperature in summer, can spray 5% lime water; anti-freeze damage at low temperature in winter, white coat on trunk, can reduce the probability of walnut being infected by pathogens.
In fact, the blackening of the black peach skin is caused by pests and diseases. Once this phenomenon occurs, it will seriously affect the quality and yield of walnuts. Therefore, you must take precautions in the process of planting walnuts. The above are detailed preventive measures. Learn from.
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