Control methods of Brown spot of Walnut

Walnut brown spot is mainly harmful to leaves and young shoots. At the initial stage of infection, gray-brown round to irregular disease spots appear in the leaves, and black spots are produced in the later stage of the disease. The leaves with heavy disease are scorched and fallen early, and the disease spots on the tender tips are dark brown, long oval and slightly sunken. Seedlings often form withered shoots. Let's take a look at the prevention and control methods of walnut brown spot.

Develop symptoms

The diseased leaves of walnut brown spot mainly harm walnut leaves, shoots and fruits. On the young leaves, the spots are brown and polygonal, while on the older leaves, the spots are round, the center is grayish brown, the edges are brown, sometimes there are yellow halos in the periphery, and sometimes perforations are formed in the central grayish brown part, and in severe cases, the spots are connected to each other. Sometimes disease spots appear on the petiole. The disease spot on the shoot is long, brown, slightly sunken, and in severe cases, the disease spot surrounds the branch and causes the upper part to die. When the fruit was damaged, the skin appeared small and slightly raised brown soft spots, then rapidly expanded and gradually sunken and blackened, there were water-stained halo lines on the periphery, and in serious cases, the nuts blackened and rotted. The old fruit was only invaded to the exocarp.

Morbidity regularity

The pathogen of walnut brown spot overwintered as conidia on the damaged leaves and shoots, and the diseased leaves and shoots after overwintering could still produce spores under suitable temperature and humidity and spread with wind and rain. The fruit is easy to be infected by bacteria before hard core, and the disease is serious when it is rainy in late spring and early summer. The severity of plant disease was related to humidity and spread rapidly after rain. the incubation period of the pathogen was 5-34 days in fruits and 8-18 days in leaves. Leaf spreading and flowering are the most susceptible to disease. The peak period of the disease is from late July to mid-August in central Hebei, and it generally occurs in Shandong from the middle to late May.

Prevention and cure method

1. Field management: clean the walnut orchard thoroughly before the spring rain, remove the diseased branches and leaves in time, bury them deeply or burn them. At the same time, strengthen the comprehensive management of walnut cultivation, enhance the tree potential, improve disease resistance, pay special attention to soil improvement, increase fertilizer application, improve ventilation and light transmission conditions.

2. Drug prevention: before the onset of walnut brown spot, "Olik-Liangguoan" was diluted and sprayed according to 300 times liquid, once in 15 days, and diluted and sprayed with "Wofengsu" according to 600 times liquid, once in 7 days. It can effectively prevent the occurrence of walnut brown spot.

2. Drug treatment: when mild onset, "Olik-Liangguoan" is diluted and sprayed with 300 times liquid, once every 10 to 15 days. If the condition is serious, it should be diluted by 200 times solution and sprayed once every 7 to 10 days. If the condition is serious, "Wofengsu" should be diluted and sprayed with 600 times liquid, once every 3 days. At the same time, strengthen orchard management, increase the application of organic fertilizer, improve tree disease resistance, pay attention to drainage after rain, and reduce orchard humidity.