The latest control methods of walnut rot

Walnut rot is caused by a kind of fungus, which is the peak in spring and autumn, especially from mid-April to late May. Generally, walnut trees with extensive management, poor soil layer, poor drainage, insufficient fertilizer and water, weak tree potential or suffering from freezing injury and salt injury are easily infected with this disease. Let's take a look at the prevention and control methods of walnut rot disease.

Symptoms of walnut rot

Walnut rot mainly harms branches, trunks, trunk and lateral branches of young trees. At the beginning of the disease spot, it is nearly fusiform, dark gray and swollen, foamy liquid is pressed by hand, the diseased skin becomes brown and has the smell of wine lees, the diseased skin loses underwater concave, and many small black spots are scattered on the diseased spot. When the humidity is high, orange-red glue gushes from the small black spots, and in severe cases, the plaque expands and causes the cortex to split longitudinally and flow out black water. The initial symptoms of the trunk infection are hidden in the phloem, but the appearance is not easy to see. When you see the symptoms, the subcutaneous disease has expanded by more than 20 to 30 centimeters, and there is sticky black water, which is often pasted on the trunk. In the later stage, black water flows out along the bark cracks and shines after drying, as if painted with a layer of black paint.

Occurrence regularity of walnut rot

The pathogen overwintered in the diseased part with mycelium or conidium and conidia. After the walnut sap flowed in the next spring, the conidia were produced under suitable conditions. The conidia were transmitted by wind, rain or insects and invaded from the graft interface, wound and so on. The disease spread gradually after the occurrence. Multiple infections can occur during the growing period, and the peak of the disease is in spring and autumn, especially from mid-April to late May. Generally, walnut trees with extensive management, barren soil layer, poor drainage, insufficient fertilizer and water, weak tree potential or suffering from freezing injury and salt injury are easy to be infected with the disease.

Control methods of walnut rot

The main results are as follows: 1. Strengthening tree management and strengthening tree potential are the basic measures to control walnut rot disease. Walnut disease resistance can be increased by deep ploughing and weeding, increasing application of organic fertilizer, reasonable intercropping, timely irrigation and drainage, reasonable pruning and so on.

2. Combine pruning after harvesting walnut, cut off the branches of diseases and insect pests, and scrape off the diseased skin. At the same time, it is necessary to do a good job in the hygiene of walnut orchards, eliminate diseased branches, withered branches and diseased branches in time, and burn them out of the garden in order to reduce the source of germs.

3. The trunk of walnut should be whitened, especially the newly planted young trees should pay more attention to white trunk in winter and summer to reduce the invasion of pathogens. The formula of whitening agent is quicklime 12 kg, salt 1.5 kg, vegetable oil 250 g, sulfur powder 500 g, water 50 kg.

4. In spring, the disease spot should be thoroughly scraped with slightly exposed new skin, and the scraping area should be about 0.5 cm wider than the discolored necrotic tissue. The scraping wound should be coated with 5-10 Bomedo stone-sulfur mixture or 1% copper sulfate solution, and then the scraped bark should be centrally burned.

5. Spraying the tree crown before or at the beginning of the disease can be sprayed with 50% carbendazim wettable powder 800x or 75% chlorothalonil 600x or 50% methyl thiophanate wettable powder 1000 times, once every 7 days for 3 times in a row.