Occurrence Patterns and Control Methods of Jujube Fruit Shrink Disease

Jujube fruit shrink disease, also known as black rot, is a new disease of jujube trees. When this disease breaks out severely, it has a serious impact on both the quality and yield of jujube fruit.

1. Symptoms

The disease mainly damages the fruit, causing fruit rot and premature fruit drop. Affected fruit first develop a pale yellow halo on the shoulder or body, which gradually expands into sunken, irregular pale yellow lesions; then the peel becomes water-soaked and infiltrated, with scattered needle-like round brown dots, the flesh turns earthy yellow, loose and soft, and the diseased tissue becomes spongy and necrotic, while the outer peel turns dark red and lusterless. Diseased fruit are small, shriveled, bitter in taste, and unfit for consumption.

2. Occurrence patterns

Jujube fruit shrink disease is caused by the combined damage of bacteria and fungi. During the immature stage of jujube fruit, fungal damage predominates, while during the near-ripe stage, bacterial damage predominates. The pathogens mainly overwinter inside diseased fruit. Generally, they spread and infect jujube fruit during the coloring and ripening stage. The pathogens invade through fruit wounds carried by wind and rain, or directly penetrate the peel. In central and southern Hebei Province, the disease begins in early July, and the peak incidence period is from mid-August to early September. The severity of the disease is closely related to environmental conditions that year such as temperature, rainfall, insect pests and variety. 22-28°C is suitable for disease development. In particular, when there is continuous overcast and rainy weather, or sunny days with rain at night and foggy weather, outbreaks are very likely to occur. Wind and rain cause leaf and fruit friction wounds, and damage from scale insects, mites, leafhoppers, stink bugs and peach fruit borers feeding on the fruit makes infection easy. Varieties such as Li jujube and Ling jujube are more susceptible, while Dong jujube and Po jujube have stronger disease resistance. In addition, excessive application of nitrogen fertilizer, dense branches and leaves, and unreasonable intercropping cause poor light and ventilation, increase pest transmission of the disease, and lead to more severe incidence.

3. Control methods

1. Manual control: After fruit harvest each year, thoroughly remove diseased and rotten fruit from the jujube orchard, burn or bury them deeply in a centralized manner, eliminate overwintering pathogens, and reduce the incidence rate the following year.

2. Chemical control: Generally, the first spray can be applied in late July or early August, and 1-2 more sprays can be applied at 7-10 day intervals. The main chemicals include streptomycin 70-140 units/ml, kanamycin 140 units/ml, and oxytetracycline 140-210 units/ml. For fungal fruit shrink disease, 75% chlorothalonil wettable powder at 600 times dilution can be used. Before the peak incidence period, spraying 50% Zaosuoguoning No. 1 wettable powder at 600 times dilution has a significant control effect.

3. Pest control: Timely control leafhoppers, tortoise wax scales, peach fruit borers and other pests that harm jujube trees, so as to reduce wounds on jujube fruit and lower the pathogen infection rate.

4. Strengthen field management: Do not intercrop tall crops or crops that share the same pests and diseases with jujube trees in the jujube orchard; prune reasonably to improve light conditions; apply more organic fertilizer and phosphorus and potassium fertilizer, apply nitrogen fertilizer and trace elements such as boron and calcium reasonably, strengthen tree vigor, and improve the disease resistance of jujube trees.