Winter and Spring Control Techniques for Apple and Pear Tree Valsa Canker and Ring Rot Dry Rot
In winter and spring, temperatures are low, and poor orchard management by fruit growers can make apple and pear orchards prone to Valsa canker and ring rot dry rot. Both are fungal trunk and branch diseases that damage the bark of fruit trees, causing it to rot, branches to die back or trunks to die, and in severe cases the entire orchard can be wiped out.
I. Disease Symptoms
Apple Valsa canker is one of the major diseases in northern apple-producing regions. It mainly affects trees over six years old, weakening tree vigor and causing branches and trunks to die back; in severe cases it can destroy an entire orchard. Pear-producing regions are likewise affected by Valsa canker.
Ring rot dry rot is also an important disease affecting apple and pear trees. Both ring rot dry rot and Valsa canker are fungal trunk and branch diseases. The incidence rate in affected pear orchards is extremely high, reaching 50%-80%. Ring rot dry rot and Valsa canker differ in the depth of the lesions, odor, cracking, presence or absence of "oily skin," the size of the black dots on the lesions, and the substances exuded from the black dots, but the causes and treatment measures for the two diseases are the same. Therefore, this article discusses these two types of diseases together.
II. Causes of Disease
Main factors:Any tree with weak vigor has a higher incidence rate.Poor site conditions, poor management, insufficient fertilization, drought and water shortage, severe spider mite, leaf drop disease and root rot, and severe alternate bearing all induce disease occurrence. Winter frost injury to the tree body, wounds, pruning and saw wounds, insect damage, and sunscald on the sunny side of branches and trunks can also induce Valsa canker. If lesions are not scraped and treated in time, and diseased dead branches are not properly disposed of after pruning, a large amount of pathogens will accumulate in the orchard and the disease will become severe.
III. Transmission and Invasion Pathways
The pathogen overwinters in diseased bark or in the xylem of diseased scars. In early spring the lesions produce conidia, which spread with wind and rain, and can also be transmitted by pests such as the pear bark miner and the apple clearwing moth. After germination they invade the tree through pruning and saw wounds, frost injuries, insect and disease wounds, or leaf scars, fruit spurs, fruit stalk scars and rhytidome with dead tissue. After invasion they lie latent in the dead and injured tissue of the bark, and when the tree or a local tissue weakens and disease resistance decreases, they cause the cortex to rot. Disease peaks occur in spring and autumn.
IV. Control Measures
Control of apple Valsa canker should adopt integrated measures centered on building up tree vigor, with timely wound protection and reducing the pathogen carried by the tree as the main preventive measures, and scraping lesions and applying chemicals as auxiliary means.
The Valsa canker control technique can be summarized as: one application, two scrapings, three sprays, four coatings (abbreviated as the "1234 method").
One application: apply organic fertilizer once after fruit harvest to build up tree vigor;
Two scrapings: scrape Valsa canker lesions twice, in early spring and late autumn;
Three sprays: spray to prevent infection after fruit harvest, when two-thirds of the leaves have fallen, 15 days before bud break in early spring for orchard sanitation, after flowering, and after harvest;
Four coatings: apply chemicals after pruning to protect wounds, coat trunks during the growing season to promote rhytidome shedding, whitewash trunks before winter to prevent frost injury, and apply chemicals after scraping to prevent recurrence.
[Specific operations]
1. Chemical protection during the dormant period
① Spray chemical protection on wounds, pruning cuts and saw cuts: pruning cuts and saw cuts are the main sites where apple Valsa canker occurs. In winter, after pruning is completed, promptly apply chemicals to protect wounds caused by pruning and all unhealed pruning and saw cuts and insect wounds from the previous year. Apply Qingye coating kit undiluted.
② Coat the trunk: the trunk is one of the main sites where Valsa canker occurs and is also where rhytidome and surface cankers form. After scraping the Valsa canker lesions in winter, dilute the Qingye coating kit with 30 jin of water and brush the trunk and the bases of main branches. This helps eradicate the Valsa canker pathogen and can also provide nutrients to the tree and enhance disease resistance. However, frost protection measures must be taken during winter scraping.
2. Control during the bud break period
Lesion scraping - scrape and treat Valsa canker lesions promptly when found in early spring and autumn. Requirements: for lesions that have reached the xylem, scrape into an oval shape with upright edges; according to the thickness of the stem, the scraped surface should extend beyond the boundary between diseased and healthy tissue, scraping 1 cm horizontally and 3 cm vertically; for lesions that affect only the phloem, simply scrape away the discolored phloem tissue. Then apply chemicals. Chemical to apply: Qingye coating kit undiluted. The chemical needs to be applied 2-3 times consecutively, at 10-day intervals, to prevent recurrence of the lesions.
3. Whitewashing trunks to prevent frost injury
Before the soil freezes in winter, prepare the whitewash: water + quicklime + salt + Kuifuling mixed in a ratio of 3::1:1:0.025, and coat the trunk to prevent frost injury. The requirement is to coat the entire trunk and coat the main branches up to 50 cm from the trunk.
4. Orchard sanitation
Purpose: to reduce the amount of pathogen in the orchard and prevent transmission of conidia.
Orchard sanitation after fruit harvest, when two-thirds of the leaves have fallen, and 15 days before bud break in early spring: spray Qingye orchard sanitation kit.
Spray prevention before and after flowering: spray Qingye nutrition kit.
5. Build strong tree vigor
① Increase organic fertilizer application. Orchards that have long used livestock and poultry organic fertilizer should switch to high-quality compost or bio-organic fertilizer, and combined application of organic and inorganic fertilizers is advocated; appropriately reduce nitrogen and phosphorus fertilizer amounts according to soil fertility conditions and yield level; pay attention to the combined application of calcium, magnesium, boron and zinc.
② Combine with high-quality, high-yield cultivation techniques such as rational pruning, straw mulching, film mulching, natural grass growing and ridging; control the total annual nitrogen and phosphorus fertilizer application with reference to the suitable fruit load and soil fertility indicators, and regulate nitrogen, phosphorus and potassium fertilizers by stages according to tree vigor and tree age.
③ Emphasize autumn base fertilizer application. Apple autumn base fertilizer should be applied promptly after harvest, using the trench method or hole application.
Therefore, in winter and spring fruit growers should strengthen orchard management to protect fruit trees from damage by Valsa canker and ring rot dry rot.
How to treat pear tree dry rot? Control methods for pear tree dry rot
Pear is a fruit that everyone relatively likes; it clears heat and reduces internal heat, and moistens the lungs and stops cough. Pear trees encounter many pests and diseases during growth. Today the editor explains the control methods for pear tree dry rot.
Symptoms of pear tree dry rot
It mainly damages branches and trunks and fruit. When branches and trunks are infected, the cortex turns brown and slightly sunken, and later the diseased branch dies back, densely covered with dark brown small granules, namely the pathogen's pycnidia. When the trunk is infected, ring-patterned canker spots appear initially; after the lesion encircles the trunk, the aboveground part dies. When fruit is infected, ring-patterned spots appear on the diseased fruit, with symptoms similar to pear ring rot, and the pathogen must be identified to distinguish them. When seedlings and young trees are infected, dark brown elongated slightly moist lesions appear on the bark, causing leaves to wilt or branches to die back. In the later stage the diseased part loses water and becomes sunken. The surrounding area cracks. And it is densely covered with small black granules.
Causes of pear tree dry rot
The occurrence of disease on branches and trunks is related to the growth condition of the tree. Weak tree vigor, continuous drought, and insufficient soil water content can all cause rapid expansion of the lesions. Generally, the disease is more severe in areas and orchards with poor water conservancy conditions, low soil fertility and extensive management, and within the same pear orchard, individual trees with weak growth vigor are more severely affected.
Control of pear tree dry rot
1. Promptly inspect and scrape off lesions: in the early stage of damage this disease is generally limited to the surface layer, so disease inspection should be strengthened and lesions scraped and treated promptly. After scraping the diseased part, apply Kuifuling undiluted;
2. Spray protection: before bud break, spray Kuifuling 300-fold dilution + organosilicon to eradicate latent infecting pathogens and prevent disease occurrence.
3. Avoid causing various mechanical wounds; for trees that already have wounds, apply Kuifuling undiluted to protect them, promote healing and prevent pathogen invasion.
4. Rational fertilization and foliar fertilizer spraying: when spraying chemicals, dilute Duodasu and Wofengsu 1000-fold and apply them at the same time, spraying evenly on the front and back of leaves to improve photosynthetic capacity and enhance the plant's disease resistance.
Damage symptoms and control methods of apple tree Valsa canker
Apple tree Valsa canker is one of the more seriously damaging diseases in apple-producing regions of China, commonly known as stinking bark disease, rotten bark disease, and girdling bark disease. In northern apple-producing regions of China, Valsa canker is very severe, with trees covered in disease scars and branches and trunks incomplete, often causing tree death and orchard destruction, and in recent years there has been a worsening trend. Below let us take a look at apple tree Valsa canker control techniques!
Damage symptoms of apple tree Valsa canker
When branches and trunks of diseased trees are affected, the lesions are of two types: canker type and branch dieback type. The canker type shows a reddish-brown, water-soaked, slightly raised diseased part; the diseased tissue is soft and rotten, often exuding yellowish-brown juice with a distillers' grain smell, and later shrinks and sinks; the diseased part has obvious small black dots (namely pycnidia), and when moist, an orange-yellow tendril-like substance emerges from the small black dots. The branch dieback type mostly occurs on small branches, fruit spurs and stub shoots; the diseased part is not water-soaked, quickly loses water and dries up, causing the whole branch to die back, with small black granules on it. When fruit is affected, the lesions are dark reddish-brown, round or irregular, with ring patterns, soft-rotten, with a slight distillers' grain smell, and obvious small black dots often in the center of the lesion.
Transmission pathways of apple tree Valsa canker
Apple tree Valsa canker mainly overwinters as mycelium, pycnidia and perithecia in diseased tree tissues and residues, and the pathogen can survive in the diseased part 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 or a local tissue weakens, it expands and spreads. Generally infection occurs from March to May, disease onset begins in July to August, early spring is the peak period of disease onset, and after late spring disease resistance increases and disease incidence drops sharply. The occurrence of apple tree Valsa canker is closely related to tree vigor, number of wounds, and healing ability; extensive management and periodic frost injury are the main epidemic factors.
Conditions for apple tree Valsa canker onset
The optimum temperature for germination of Valsa canker conidia and ascospores is 25-30°C, and they can also germinate at 5°C after a long period. Extensive cultivation management and frost injury are the main inducing factors for Valsa 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, excessive fruiting, severe alternate bearing, and early leaf drop that cause weak tree vigor all have more severe disease, and vice versa. Orchards in low-lying areas where water accumulates too long in the later period, and orchards prone to frost injury due to excessive vegetative growth and delayed dormancy, also have severe disease. Periodic frost injury in the north, causing large-area bark frost injury to trees, is an important reason for large-scale Valsa canker epidemics.
Control techniques for apple tree Valsa canker
1. Strengthen cultivation management: strong trees resist disease; prune rationally, adjust tree vigor, regulate tree load, overcome alternate bearing, increase organic fertilizer application, rationally combine nitrogen, phosphorus, potassium fertilizers and medium and trace elements, do a good job of cold protection for fruit trees to reduce frost wounds, and whitewash bearing trees. Commonly used whitewash: lime:salt:water:animal oil (10:1:30-35:0.2). It is generally applied after fruit trees lose their leaves, coating the trunk to a height of 2 m.
2. Promptly clean the orchard: promptly cleaning the orchard can reduce pathogens. Scrape and treat lesions promptly when found. During pruning, take care to remove diseased branches, residual stubs and diseased fruit spurs; promptly remove and burn pruned diseased branches and dead diseased trees; seal pruning and saw cuts and other wounds with chemicals or paint to reduce pathogen invasion pathways.
3. Use chemical prevention: spray fungicides before the tree body breaks dormancy in early spring. Chemicals include Gerun or Shinaning aqueous solution 500-fold dilution, 3-5 degree lime sulfur mixture, 5% Junduqing aqueous solution 500-fold dilution, etc. From June to July, the above chemicals can be used to brush large branches and trunks of the tree; continuous control over several years has obvious effects.
4. Use diseased scar treatment
① Scraping method: cut a protective ring reaching the xylem with a knife 0.5 cm beyond the edge of the diseased scar, then thoroughly scrape away the diseased bark and healthy bark within the ring, and collect the diseased tissue scraped onto a plastic sheet and burn it. For the exposed xylem, cut deeply 1-1.5 cm with a knife and then apply chemicals. Gerun 5-fold dilution, 5% Junduqing aqueous solution 5-fold dilution, etc. can be used for application, and apply once more 20 days after treatment.
② Mud poultice method: mix water and soil into a mud cake, apply it to the diseased scar and a 5-8 cm surrounding area, 3-4 cm thick, then tie tightly with plastic sheet or kraft paper. This method is suitable in spring; remove the wrapping in the following spring, clear the diseased residual tissue, and apply chemicals for disinfection and protection.
③ Foot grafting method: using foot grafting (or bridge grafting) can improve the tree's ability to transport nutrients and water, help restore tree vigor, and extend the fruiting years. This method is widely used in old fruit regions and can be actively promoted in new fruit regions.