There are often walnut growers asking: Is black walnuts awkward? How to do? In fact, this is one of the common diseases of walnuts, known as walnut bacterial black spot. It mainly harms the leaves, fruits and young shoots of walnuts, which can cause fruit to fall off or even fail.
First, the symptoms of harm
In the early stage of the disease, small brown lesions appeared in the vicinity of the veins, and there were yellow halos around the periphery. The central gray-brown part formed perforation in the late stage. In severe cases, the lesions were connected to each other; the lesions on the branches were long, brown, slightly concave, and severely diseased. The plaque surrounds the branches and causes the upper part to die; the surface of the fruit suffers from a small, slightly bulging brown soft spot, which then rapidly enlarges and becomes dark and sag, with watery stains on the periphery, and the nucleolus becomes black and rot in severe cases.
Second, the law of incidence
The pathogenic bacteria mainly overwinter on the diseased branches, diseased fruits, diseased leaves and diseased buds, and the length of the disease incubation period is closely related to the host. The incubation period in the fruit is 5-34 days, 8-18 days in the leaves, and generally only 15 days in field conditions.
The occurrence of the disease is closely related to rainwater. In the years with heavy rain, the incidence is heavier, and in dry years, the incidence is lighter. In addition, it also determines the degree of tenderness of the various parts of the host, the state of water accumulation in the tissue and the size of the opening of the pores. In the case of young tissue, large open pores and many wounds, the disease occurs more seriously.
Third, prevention and treatment methods
1. Thoroughly clean the walnut garden after defoliation, and timely remove the diseased fruit, branches and leaves of the tree, buried or burned;
2. Strengthen the comprehensive management of walnut trees, timely supplement nutrition, apply more phosphorus and potassium fertilizer, enhance tree potential, improve disease resistance, and use less sticks to knock when harvesting fruits, reducing tree wounds;
3. Pay attention to keep the inside of the canopy ventilated and light, trim the inner lychee and long branches, and use the 1500 times of the eucalyptus + 1000 times of the sensation before the onset to prevent the occurrence and spread of the disease.
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