Identification and Prevention of Branch Blight of Walnut

1. Symptoms mainly harm walnut stems, resulting in dead and dry stems. When severe, they cause a large number of shoots to die and the yield drops. The disease begins with young shoots and then spreads down to the trunk. The affected branch of the cortex was dark gray at first, then it turned reddish-brown, and finally turned dark gray. And many small black spots (ie, pathogenic conidia discs) were formed, and the leaves of infected branches gradually became yellow, fell off, and the branches died. When the humidity is high, the disease minister produces a large number of black short columns (ie, conidia).

II. Pathogen Melanconium oblongum Berk is said to be a subphylaxis fungus of the subphylum Aspergillus subtilis, which is buried in the epidermis of the host and then breaks through the epidermis. Conidiophores are densely formed on the conidia disc. Light gray, conidial spores apical, oval to round, more than two ends blunt. Some ends are slightly pointed and dark brown.

Third, the route of transmission and the incidence of pathogenic bacteria mainly in the spores or mycelium in the branches, trunk disease overwintering. Conidia produced at appropriate conditions in the following year spread by wind and rain or spread by insects and invade the wound. The fungus is a weakly virulent strain, and it is easy to grow diseased walnut trees or branches. The incidence is severe in the early spring or in the cold.

Fourth, control methods

1, biological control:

(1) Increase organic fertilizers, increase tree vigor, and increase disease resistance.

(2) The diseased branches are cut off in time for the growing season and buried or burned.

(3) Autumn trunks are painted white to prevent freezing damage.

(4) Main disease, scraping the lesions, disinfecting the wound with 1% copper sulfate solution, and applying a wound healing agent such as a healing healing paste.

2. Chemical control: In the period of 6-8 months, use 70% thiophanate-methyl WP 800-1000 times solution or Manson Mn-Zn WP 100-500 times spray control, spray once every 10 days, even spray 3-4 times, the effect is good.

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