What is walnut branch blight? Get to know this walnut disease
How to grow walnuts efficiently? Please give guidance. Walnut cultivation can refer to the following planting methods: Seedling selection: high-quality seedlings should be selected for planting. High-quality seedlings refer to those with pure varieties, well-healed graft unions, more than 15 lateral roots, a basal stem diameter of more than 1.2 cm, a seedling height of more than 60 cm, straight and smooth stems, and no damage or pests and diseases...
What is walnut branch blight? What methods can prevent and control it? Please introduceWalnut branch blight:
1. Symptoms It mainly harms walnut branches and trunks, causing dead branches and dead trunks, and in severe cases causes a large number of branches to die, reducing yield. The disease first starts on young short branches, then spreads downward to the trunk. The cortex of affected branches is initially dark gray, then becomes light reddish brown, and finally turns dark gray. And many small black grain-like spots form (that is, the pathogen's acervuli), the leaves of infected branches gradually turn yellow, fall off, and the branches die. When humidity is high, a large number of black short columnar bodies grow on the diseased area (that is, conidia).
2. Pathogen Melanconium oblongum Berk, called rectangular black disk spore, belongs to the Deuteromycotina fungi. The acervuli are embedded in the host epidermis, then break through the epidermis and become exposed. The conidiophores are densely borne on the acervuli. They are light gray. The conidia are borne at the tips of the conidiophores, oval to round, mostly with bluntly rounded ends. Some have one end slightly pointed, dark brown.
3. Transmission routes and disease conditions The pathogen mainly overwinters as acervuli or mycelium in the diseased parts of branches and trunks. The conidia produced under suitable conditions the following year spread through wind and rain or insects, and invade through wounds. This fungus is a weak pathogen, and weak-growing walnut trees or branches are susceptible to the disease. In years with spring drought or freezing damage, the disease is severe.
4. Control methods
1. Biological control:
(1) Apply more organic fertilizer to strengthen tree vigor and improve disease resistance.
(2) During the growing season, promptly prune diseased branches and bury them deeply or burn them.
(3) In autumn, whitewash the trunks to prevent freezing damage.
(4) If the trunk is diseased, scrape off the diseased spots, disinfect the wounds with 1% copper sulfate solution, and apply a healing ointment or other wound protectant externally.
2. Chemical control: From June to August, use 70% thiophanate-methyl wettable powder at 800-1000 times dilution or mancozeb wettable powder at 100-500 times dilution for spray control, spraying once every 10 days, for 3-4 consecutive sprays, with good results.
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