Latest Technical Methods and Tutorial for Preventing and Treating Apple Tree Canker
Apple tree canker is one of the more serious diseases affecting apple-producing areas in China, commonly known as stinky bark disease, rotten bark disease, and running bark disease. In the northern apple-producing areas of China, canker occurs very severely, with trees covered in disease scars and branches and trunks incomplete, often causing tree death and orchard destruction. In recent years there has been a worsening trend. Let us take a look together at apple tree canker prevention and treatment techniques!
Symptoms of Apple Tree Canker Damage
When branches and trunks of diseased trees are affected, the lesions have two types: canker type and branch blight type. In the canker type, the diseased area is reddish-brown, water-soaked, slightly raised, with the diseased tissue soft and rotten, often exuding yellowish-brown sap with a vinasse smell; later it shrinks and sinks, and the diseased area has obvious small black dots (pycnidia). When moist, an orange-yellow tendril-like substance oozes from the small black dots. The branch blight type mostly occurs on small branches, fruit spurs, and dry stubs; the diseased area is not water-soaked and rapidly loses water and dries up, causing the entire branch to die, with small black dots forming on it. When fruit is affected, the lesions are dark reddish-brown, round or irregular, with concentric rings, soft-rotten, with a slight vinasse smell, and the center of the lesion often has obvious small black dots.
Transmission Routes of Apple Tree Canker
Apple tree canker mainly overwinters as mycelium, pycnidia, and perithecia in diseased tree tissues and residues. The pathogen can survive in diseased areas for about 4 years. The following year, conidia are released from the pycnidia and spread by rain splash, invading through wounds. The pathogen has latent infection characteristics; when the tree body or its local tissues weaken, it will expand and spread. Generally, infection occurs from March to May, disease onset begins in July to August, with the early spring being the peak period of onset. After late spring, disease resistance increases and disease incidence drops sharply. The occurrence of apple tree canker is closely related to tree vigor, number of wounds, and wound-healing ability. Extensive management and periodic freeze damage are the main epidemic factors.
Conditions for Apple Tree Canker Onset
The optimal temperature for germination of canker pathogen conidia and ascospores is 25-30°C, and they can also germinate at 5°C after a relatively long period. Extensive cultivation management and freeze damage are the main predisposing factors for canker epidemics. Orchards with low soil organic matter, compacted soil or poor water and fertilizer retention, poor root growth, insufficient compound fertilizer, excessive nitrogen fertilizer application, excessive fruiting, severe alternate bearing, and early defoliation that cause weakened tree vigor all have more severe disease incidence, and vice versa. Orchards in low-lying areas with prolonged waterlogging in the later period, as well as those prone to freeze damage due to excessive vegetative growth and delayed dormancy, also have severe disease incidence. Periodic freeze damage in the north, causing large-scale bark frost injury to tree bodies, is an important reason for large-scale canker epidemics.
Apple Tree Canker Prevention and Treatment Techniques
1. Strengthen cultivation management: Strong trees resist disease. Prune reasonably, adjust tree vigor, regulate tree load, overcome alternate bearing, increase organic fertilizer application, reasonably balance nitrogen, phosphorus, and potassium fertilizers with medium and trace elements, do a good job of fruit tree cold protection, reduce freeze wounds, and apply whitewash to bearing trees. The commonly used whitewash formula is lime:salt:water:animal oil (10:1:30-35:0.2). It is generally applied after fruit trees drop their leaves, with a trunk coating height of 2 m.
2. Clean the orchard in a timely manner: Timely cleaning of the orchard can reduce pathogens. When disease lesions are found, scrape them off promptly. During pruning, pay attention to removing diseased branches, residual stubs, and diseased fruit spurs. Pruned diseased branches and dead diseased trees should be removed and burned promptly. Pruning and saw cuts and other wounds should be sealed with chemicals or paint to reduce pathogen infection routes.
3. Use chemical prevention: Spray fungicides before tree bodies sprout in early spring. Chemicals include Green or Shenaning aqueous solution at 500 times dilution, 3-5 degree lime sulfur mixture, 5% Jun Du Qing aqueous solution at 500 times dilution, etc. From June to July, the above chemicals can be used to brush large branches and trunks of the tree body. Continuous treatment over several years has obvious effects.
4. Use lesion treatment
① Scraping method: Around the lesion, extend 0.5 cm outward and cut a protective ring deep to the xylem with a knife, then thoroughly scrape off the diseased bark and healthy bark within the ring. The diseased tissue scraped onto plastic sheeting should be collected and burned. For the exposed xylem, cut deeply 1-1.5 cm with a knife and then apply chemical treatment. Green at 5 times dilution, 5% Jun Du Qing aqueous solution at 5 times dilution, etc. can be applied. After treatment, apply again 20 days later.
② Mud application method: Mix water and soil into a mud cake, apply it to the lesion and its surrounding 5-8 cm area, 3-4 cm thick, then tie tightly with plastic sheeting or kraft paper. This method is best carried out in spring. In the following spring, remove the wrapping material, clear the diseased residual tissue, and apply chemical disinfectant protection.
③ Foot grafting method: Using foot grafting (or bridge grafting) can improve the tree body's ability to transport nutrients and water, help restore tree vigor, and extend the fruit-bearing years. This method is widely used in old fruit areas and can be actively promoted in new fruit areas.