Excuse me, experts, how to prevent jujube brown spot disease

Jujube brown spot, also known as jujube black rot, is an important disease in jujube areas in southern China. It is mainly distributed in Guangxi, Sichuan, Yunnan and other places, and also occurs in a large number of jujube areas in the north. In recent ten years, the disease has become more and more serious. As the main jujube producing areas in Sichuan, disasters have occurred one after another in Meishan, Xichang and Guanghan. In epidemic years, the rate of diseased fruit is as high as 50%, and in severe cases it can reach more than 70%, or even no harvest.

Symptoms (1) The disease mainly harms fruits, making them rot and fall off early. Generally, in June and July, when the jujube fruit swells, turns white and is about to be colored, a large number of diseases begin. At the early stage of jujube fruit damage, pale yellow irregular spots appeared on the shoulders or trunk with clear edges, and then the spots gradually expanded, and the affected parts were slightly sunken or wrinkled. The color deepened to reddish brown, and finally, the whole diseased fruit was dark brown and lost its luster. When the diseased fruit is cut open, you can see that the pulp of the diseased part is yellowish and mottled. In severe cases, most of the pulp turns brown until the whole pulp turns brown and finally turns gray-black to black. The diseased tissue is spongy necrosis, bitter in taste and inedible. In the late stage (September), brown spots appeared on the fruit surface, which gradually expanded and grew into oval lesions. Flesh soft rot, serious fruit soft rot. Generally, jujube fruit falls off early 2 ~ 3 days after onset. After the diseased fruit fell to the ground, many small black spots could grow on the diseased part under wet conditions, which is the conidia of pathogenic bacteria. After overwintering, a large number of dark brown spherical protrusions are produced on the surface of diseased fruits, which are conidia of pathogenic bacteria.

(2) Pathogenic fungi (Hemiptera subfamily) and aggregated small cell fungi. The daughter tissue of the pathogen was born under the epidermis of the host, and it broke through the epidermis and was exposed after maturity, showing a spherical bulge.

There are 1 to several conidia in each daughter. Conidia are nearly round with obvious pores, and the size is 34 1.3 ~ 160.3 μ m× 325 ~130 μ m. Conidiophore and conidia are colorless, the conidia are spindle-shaped or spindle-shaped, single cell, and the size is 29.2 ~ 18 μ m× 7.2 ~ 4.3 μ m (Figure 14 ~ 1 and 14-2).

(3) Disease cycle and epidemic pathogens overwinter on diseased branches and dead branches with hyphae, conidia and conidia. After the jujube tree germinated in the second year, conidia spread through wind and rain, insects and so on. Invasion from insect wounds, natural orifices or directly through the skin of jujube fruit. The pathogen began to infect after flowering and early fruiting, but it did not get sick and was in a latent state after invasion. When the fruit approaches maturity, the physiological and biochemical changes of pulp tissue and sugar content increase significantly, and the latent hyphae expand rapidly, causing fruit diseases. The reason why jujube fruit is easy to soften and rot when it is ripe is that with the ripening and aging of the fruit, the wax and horny membrane of the peel are thickened, the air permeability is weakened, the respiration of the fruit itself is enhanced, and the fruit is easy to release ether, which promotes the softening and accelerated decay of the fruit. When the humidity of fruit is high at maturity, conidia will be produced in that year, which will infect the fruit again. Through indoor and field artificial inoculation, it is proved that the incubation period of the disease is only 2 ~ 7 days, so the disease occurs quickly.

Fig. 14 pathogen of jujube brown spot 1. Spore 2. The occurrence time and severity of conidia are closely related to the rainfall in that year and the relative humidity of air in jujube orchard. In rainy years, the onset is early and severe; On the contrary, it happens late and lightly; Especially from mid-June to early August, if there are more rainy days, the disease will break out.

The incidence is related to the strength of trees. Weak trees are early and heavy, while strong trees are late and light. The disease is related to tree girdling and girdling. Field investigation shows that girdling and girdling trees have few new shoots, thin leaves and weak leaves, which cause early onset and serious harm.

The disease is related to varieties in intercropping crops. When planting tall crops such as corn between rows of jujube trees, the disease is serious because of poor ventilation and light transmission, high humidity. Jujube orchards intercropped with beans and cotton are seriously ill because there are many stinkbug insects and fruit eaters, which harm fruits and cause many wounds. Intercropping low-stalk crops such as peanuts and sweet potatoes in jujube orchard has good ventilation and light transmission, low humidity and light diseases.

(4) Early prediction. According to the observation in Meishan area, Sichuan, the disease first occurred on plants with weak tree vigor and serious illness in history, and diseased fruits appeared. The onset of the disease is closely related to the arrival of rain after fruit setting, rainfall and air relative humidity. When the relative humidity of air is 80%, the onset of disease can be predicted.

2 peak period. The time to enter the peak period depends on the number of rainy days and rainfall near the fruit maturity from late June to early August. If it rains continuously for 2 ~ 3 days, and the relative humidity reaches above 98%, the peak incidence can be predicted.

③ Duration. The length of the peak period depends on the end of the rainy season.

(5) Prevention and control methods ① Do a good job in clearing the garden. Remove the dead fruit from the ground and bury it deeply. For jujube orchards or plants with serious diseases, pruning should be combined with fine pruning to cut off dead branches, focus on burning pests and diseases, and reduce the source of diseases.

② Strengthen the comprehensive management, increase the application of organic fertilizer and phosphorus and potassium fertilizer, and enhance the tree vigor. Scientifically use "Tianda 2 1 16" to improve the disease resistance. Tall crops such as peanuts and sweet potatoes should be planted between rows of jujube orchards, and tall crops such as corn should not be intercropped, so as to keep the jujube orchard ventilated and transparent, reduce the air humidity and reduce the occurrence of diseases.

③ Spray protection.

A. Spraying 65,438+000 times of 40% thiram wettable powder or 5 Baume lime-sulfur mixture+65,438+000 times of sodium pentachlorophenol solution 5-65,438+000 days before germination to eliminate overwintering germs on trees.

B. Spraying "Tianda 2 1 16" in young fruit stage to control rust and other diseases, and spraying 10 ~ 05 days/800 ~ 1 000 times of 50% fenpropabamectin wettable powder solution (developed by Plant Protection Department of Henan Agricultural University

C, spraying 1 200 times Bordeaux solution every 20 days after young fruits set, and alternately using with the above liquid medicine.