Integrated Prevention and Control Methods and Technical Key Points for Prickly Ash Diseases
Prickly ash (scientific name: Zanthoxylum bungeanum Maxim.), also known as hui, dajiao, Qin pepper, Shu pepper, Chuan pepper or mountain pepper. It is a deciduous shrub or small tree of the genus Zanthoxylum in the Rutaceae family, and can be planted as a solitary specimen or used as a protective thorn hedge. Its fruit peel can be used as a seasoning, and aromatic oil can be extracted from it; it can also be used as medicine, and its seeds can be eaten or processed into soap. Prickly ash is not only one of the most commonly used seasonings, but also a traditional Chinese medicine. It can warm the middle and relieve pain, remove dampness and dispel cold, and so on. Prickly ash enters the lung, kidney and liver meridians, and has the effects of dispelling cold, tonifying kidney yang, improving eyesight, promoting digestion and guiding fire back to its source. Soaking the feet in prickly ash water and soaking the feet in angelica and safflower have similar effects, both can promote blood circulation and dredge collaterals, keeping the blood vessels of the whole body unobstructed.
During the growth and development of prickly ash, due to unsuitable environment or invasion by pathogenic bacteria, diseases often occur that affect the growth, fruit bearing and fruit setting of the pepper tree, as well as product quality. Common diseases include prickly ash dodder, prickly ash rust, prickly ash root rot, prickly ash leaf fall disease, prickly ash anthracnose, prickly ash canker, prickly ash shoot blight, prickly ash branch blight, prickly ash leaf spot, prickly ash plaster disease, etc. The main ones introduced here are prickly ash root rot, prickly ash rust and prickly ash plaster disease.
1. Prickly ash root rot
Prickly ash root rot often occurs in nurseries and mature pepper orchards. It is a soil-borne disease caused by Fusarium solani. The roots of affected plants become discolored and rotten, with an off-odor; the root bark separates from the xylem, and the xylem turns black. The aboveground parts have small, yellow leaves, and the branches develop incompletely. In severe cases, the entire plant dies.
Prevention and control measures:
① Reasonably adjust the layout, and improve pepper orchards with poor drainage and a damp, shady environment so that they are well ventilated and dry.
② Do a good job in seedling-stage management, strictly select nursery sites, and disinfect the soil with a 500-800 times dilution of 15% triadimefon. Use raised beds with deep furrows, and apply heavy base fertilizer. Remove diseased seedlings in time.
③ When transplanting seedlings, soak the roots in a 500 times dilution of 50% thiophanate-methyl for 24 hours. Disinfect the soil with quicklime. Also drench the roots with a 500-800 times dilution of thiophanate-methyl, or a 500-800 times dilution of 15% triadimefon.
④ In April, drenching mature trees with a 300-800 times dilution of 15% triadimefon can effectively prevent the disease from occurring. Root drenching in summer can slow the severity of the disease, and root drenching in winter can reduce the overwintering structures of the pathogen.
⑤ Promptly dig out diseased and dead roots and dead trees, and burn them to eliminate sources of infection.
2. Prickly ash rust
Prickly ash rust is one of the important leaf diseases of prickly ash. It is widely distributed in prickly ash cultivation areas in Shaanxi, Sichuan, Hebei, Gansu and other provinces. In severe cases, prickly ash defoliates early, directly affecting fruit setting the following year. At the early stage of the disease, 2-3 mm water-soaked chlorotic spots appear on the upper surface of the leaves, and yellow-orange blister-like structures, which are uredinia, appear on the lower leaf surface opposite the lesions. This disease is caused by Coleosporium zanthoxyli. The uredinial and telial stages occur on the prickly ash tree. The occurrence of prickly ash rust is mainly related to climate. Wherever rainfall is abundant, especially when there is a lot of rain and many rainy days in the third quarter, damage is very likely to occur.
Prevention and control measures:
① Chemical prevention: before the disease occurs, spray Bordeaux mixture or 0.1-0.2% Baume lime-sulfur mixture, or from early June to late July spray prickly ash trees with a 200-400 times dilution of carboxin for protective spraying.
② Chemical control: for trees that have already developed the disease, spray a 1000 times dilution of 15% triadimefon wettable powder to control the production of uredinia. At the peak of the disease, spray a 1:2:200 Bordeaux mixture, or 0.1-0.2 Baume lime-sulfur mixture, or a 1000-1500 times dilution of 15% wettable triadimefon powder.
③ Strengthen fertilizer and water management, remove weeds, and prune reasonably. In late autumn, promptly remove dead branches, fallen leaves and weeds and burn them. ④ Cultivate disease-resistant varieties, and mixed planting of prickly ash varieties with strong disease resistance can be carried out.
3. Prickly ash plaster disease
Prickly ash plaster disease is a common disease of prickly ash, and its pathogen is Septobasidium of the Basidiomycota subphylum. The basidiocarp is plaster-like and clings tightly to the branches and trunks of prickly ash. In mild cases, it causes poor growth of branches and trunks and fewer fruits; in severe cases, it causes branches and trunks to die. In many areas, dead branches and trunks, few fruits, and small fruits of prickly ash are all related to plaster disease. The occurrence of plaster disease is related to tree age, humidity and variety. According to surveys, prickly ash plaster disease mainly occurs in shaded, humid mature pepper orchards; in addition, the occurrence of this disease is related to damage by scale insects. Plaster disease uses the honeydew secreted by scale insects as nutrition, so in pepper orchards with severe scale insect damage, plaster disease occurs severely.
Prevention and control measures:
① Strengthen management, prune appropriately, remove dead branches and fallen leaves, and reduce the humidity of the pepper orchard.
② Control planting density, especially in old mature pepper orchards in full fruit period; where it is too shaded, thinning should be carried out appropriately.
③ Apply 4-5 degrees Baume lime-sulfur mixture to the diseased spots.
④ Strengthen the control of scale insects.
4. Prickly ash gummosis
Prickly ash gummosis is caused by fungi and is highly contagious. It can rapidly cause necrosis, rot and gum exudation in the phloem at the base of the trunk, leading to leaf yellowing and branch death.
Prevention and control methods:
① Clean the orchard and disinfect it. Cleaning in winter should be thorough. Gather diseased branches and leaves and burn them or bury them deeply, and at the same time spray "Hushu Jiangjun" for whole-orchard disinfection.
② Spray medicine at the appropriate time, carry out prevention well, and promptly increase the application of organic fertilizer. At the early stage of the disease, spray fungicide in time. Apply "Hushu Jiangjun" promptly at the gum exudation openings to prevent and control prickly ash gummosis; this can dredge the conducting vessels and improve the stress resistance of the plant.
③ Ensure sufficient fertilizer and water, and remove weeds. At the flower bud stage, young fruit stage and fruit expansion stage of prickly ash, spray "Huajiao Zhuangdi Ling" once each time to improve the disease resistance of prickly ash trees. At the same time, it can make the prickly ash peel thick, the pepper fruits plump, the color bright, and the natural flavor rich and fragrant.
④ Chemical control. Gummosis (dry rot) often occurs together with longhorn beetles and jewel beetles, so longhorn beetles and other pests and diseases should be controlled in time, and targeted pesticides plus "Xin Gao Zhi Mo" should be sprayed to enhance the efficacy, prevent the invasion of airborne pathogens, and spray "Hushu Jiangjun" throughout the orchard for disinfection.