Walnut trunk branches, if only a small branch dry, it is due to spawning in the sprig. If large branches occur, or the occurrence of branchlets is more common, it is caused by locust or branch blight. Diseases need to be combined with multiple organic fertilizers and sprayed with systemic pesticides or biological pesticides.
Branch blight fungal disease mainly damages the dried walnut branches, resulting in dead branches and withered stems. In severe cases, it can cause a large number of shoots to die and has a great impact on the yield. The disease begins with young shoots and then spreads down to the trunk. The affected branch cortex was dark gray at first, then turned reddish-brown at the end, and finally turned dark gray, and formed many small black spots (ie, the conidia plate of the pathogen). The leaves on the diseased branches gradually turned yellow and fell off, and the branches died. When the humidity is high, the disease minister produces a large number of black short columns (ie, conidia). Mycelia and conidia discs in winter in the diseased part of the disease, contagious spores are produced in late spring conditions, spread by wind and rain, insects. The onset usually begins in May-June, and the onset occurs in July-August; the incidence of severe branches and freezing injury or severe drought in spring is serious.
Control methods
(1) Agricultural control. Increase organic fertilizers, increase tree vigor, and increase disease resistance; timely cut off diseased branches in the growing season and burn them; autumn trees are painted white to prevent freezing damage; main diseases can be scraped off, and 1% copper sulfate solution is used to disinfect wounds. Apply a wound protection agent.
(2) Chemical control. In 6-8 months, use 70% thiophanate-methyl WP 800-1000 times or mancozeb WP 400-500.
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