Causes of Root Rot in Oilseed Peony and Its Control Measures
How to control root rot in oilseed peony? What are the specific control measures? In recent years, root rot in oilseed peony has occurred rather severely, especially in rainy years, often causing the death of entire plants or even whole patches. Below, the editor of Huinong Network summarizes the occurrence patterns and control of root rot in oilseed peony.
1 Occurrence patterns
The pathogen of root rot in oilseed peony is Fusarium solani, a fungus of the subphylum Deuteromycotina. It occurs mostly in the rainy season, caused by poor field drainage, prolonged waterlogging and a humid environment, and is related to some extent to soil pests and continuous cropping. Peony roots have a sweet taste, and soil pests bite and feed on the peony roots, forming wounds that allow the pathogen to invade. In addition, improper fertilization, with low-quality fertilizer, large granules, or fertilizer applied to the soil without fermentation, increases the pathogens in the soil and causes damage to the peony roots.
2 Main symptoms
Root rot mainly damages the roots. After part of the root system is infected, irregular black spots appear on the root bark, which continuously develop and cause the branch roots to turn black, spreading to the main root and causing all roots to turn black and rot. The aboveground part grows weakly, the leaves turn yellow, and part of the leaf mesophyll turns yellow; in severe cases, the leaves and branches die. If not controlled in time, the entire plant will die.
3 Control measures
3.1 Soil disinfection
When ploughing the soil, carry out soil disinfection, broadcasting 3~5 kg per mu of phoxim or isofenphos-methyl granules to control underground pests.
3.2 Soaking roots in medicinal solution
Before planting seedlings, soak the seedling roots in a 600~800 times dilution of thiophanate-methyl solution for 2~3 minutes, then air-dry and plant.
3.3 Drainage and crop rotation
During the rainy season, drain promptly to reduce water accumulation in the field. Avoid continuous cropping, implement crop rotation, and reduce the long-term accumulation of pathogens and the damage they cause.
3.4 Chemical control
Use nutrient-pot seedling raising and transplanting to prevent root wounds. In the early stage of the disease, drench the roots with a 150 times dilution of Genfu Suzhi, using it 3 times consecutively at half-month intervals. When diseased plants are found, dig them out promptly and burn them, and disinfect the diseased holes with lime.
That is all for today's content. Nowadays more and more people are starting to grow oilseed peony, because it has special significance for farmers in adjusting their planting structure and escaping poverty to become prosperous. If you also have ideas, first follow Huinong Network to learn planting techniques.
Control Measures for Violet Root Rot in Peony
Violet root rot of peony, commonly known as purple or black root rot or root decay disease, is a common fungal disease of peony. Old plants and plots with many years of continuous cropping have a higher incidence. Besides peony, it also harms forest trees, fruit trees and crops.
SymptomsIt mainly harms the plant root system and the root collar. The young tender roots are infected first, gradually spreading to the lateral roots, main root and root collar. In the early stage of the disease, a yellow-brown wet rot appears at the diseased part, turning deep purple or black in severe cases. A layer of cotton-like mycelium is produced on the surface of the diseased roots, and in the later stage the surface layer of the diseased roots completely rots and separates from the xylem. This disease has a long damaging period; affected plants usually die only after 3~5 years or longer. Affected plants show weakened growth vigor, yellowing, and smaller leaves, and bear flowers in alternate years; in severe cases, some branches or the entire plant die. Once cotton-like mycelium emerges at the root collar of the plant, it proves that most of the underground part has rotted, and the plant will die quickly.
PathogenThe pathogen is the purple corticioid fungus Helicobasidium purpureum (Tul.) Pat., a fungus of the subphylum Basidiomycotina. The fruiting body is membranous, purple or purplish red. The hymenium faces upward and is smooth. The basidia are curled, and the basidiospores are single-celled, kidney-shaped and colorless.
Occurrence patternsThe pathogen overwinters in the soil as rhizomorphs or sclerotia, or as mycelium in diseased residues. The pathogen in the soil can survive for 3~5 years. When conditions are suitable, the pathogen germinates and grows vegetative hyphae, invades the young roots of the host, and then spreads to the main root or lateral roots. In May~June it produces basidia and basidiospores, and the basidiospores germinate to produce hyphae. The pathogen spreads in the field through irrigation water or rainwater, farm tools, etc. Good soil permeability, a water-holding capacity of 60%~70%, and pH 5.2~6.4 are most suitable for the growth and development of the pathogen. Low-lying land, poor drainage, heavy clay soil and plots with high soil organic matter content have severe occurrence; too-dry soil also has severe incidence. In July~August each year, when there is more rain, the disease occurs more severely.
Control measures
1. Strictly disinfect seedlings and soil
Soak the seedling roots in 20% lime water for half an hour, or in a 100 times dilution of Bordeaux mixture for 1 hour, then soak the roots in 1% copper sulfate solution for 3 hours. Then wash them clean with water and plant. For soil disinfection, before ploughing, apply per mu 5-7.5 kg of 2.5% Ceresan powder or 2.5-5 kg of pentachloronitrobenzene powder, or 10-20 kg of sulfur powder, and turn it into the soil. For small-area planting, disinfect the seedbed or tree holes by spraying with a 500 times dilution of 30% liquid "Dijunxiao", using 3 liters per square meter.
2. Strengthen soil water and fertilizer management
The main cause of root rot is mostly soil infection caused by the application of organic fertilizers such as human excrement and urine that have not been fully decomposed and fermented. Therefore, to strengthen soil water and fertilizer management, the main measures are:
① Increase potassium fertilizer to promote new root growth. During the growing period, 0.1-0.2% potassium dihydrogen phosphate can be used for foliar spraying, or potassium sulfate or potassium chloride (do not use in saline-alkali land) can be added during fertilization, at 5-7.5 kg per mu.
② Carry out reasonable intertillage and winter ploughing, so that the cultivated soil layer of the peony garden is kept at about 25 to 30 cm, preventing soil compaction and keeping the soil loose with good water and air permeability.
③ Avoid raw fertilizer and heavy fertilizer. Use little or no human excrement and urine; if organic fertilizers such as human excrement and urine are applied, they must be fully decomposed and fermented.
④ Control underground pests promptly. Root stocks bitten open by white grubs are prone to root rot infection. Therefore, in early spring each year, promptly spray an 800 times dilution of trichlorfon or a 1000 times dilution of phoxim.
⑤ Properly control the frequency and amount of watering for peony, especially in early spring and late summer during the active period of mycelium. When the soil moisture content is not less than 60%, water as little as possible or not at all, to reduce infection.
3. Carry out root drenching treatment
For severely diseased plants, dig them out and burn them, or cut off the diseased roots, disinfect them and replant. For newly infected plants or those with mild disease, open trenches and carry out root drenching treatment. The following drugs have a certain curative effect on root rot and can be selected for use: 1 degree Baume lime-sulfur mixture (2.5-7.5 kg/plant); 200-500 times copper sulfate solution (5-7.5 kg/plant); 500-800 times wettable powder of Tuzet (1.5-2.5 kg/plant); 1000 times dilution of 70% thiophanate-methyl (1.5-2.5 kg/plant). In early spring or late summer, dig 3-5 radial trenches around the trunk, as long as the canopy, 20-30 cm wide and about 30 cm deep, so that the roots are better exposed; after drenching with the medicine, cover with soil.
4. Replace soil with sand
Dig out the soil around the root collar of the diseased plant, replace it with clean new sandy soil, and replace it again after half a year.
5. Air-dry the roots and dig trenches for isolation
Dig away the soil around the diseased plant to expose the diseased roots to the air. Through sunlight exposure and ventilation, the development of the disease can be reduced and inhibited; this can be done from early spring to late autumn. In addition, between diseased and healthy plants, depending on the distribution depth of the plant roots, dig trenches 60-80 cm deep to prevent and block the extension of mycelium and the resulting contact infection.
6. To prevent the spread and infection of peony root rot, pine and cypress trees should be planted around the peony garden; poplar, willow, locust and white wax trees should not be planted.
Occurrence Patterns and Control Methods of Peony White Grubs
[Damage] White grubs is the general name for the larvae of scarab beetles, and is a common stubborn pest in peony gardens. It lives in the soil and mainly harms the root and stem parts of peony, Chinese peony and other flowering trees and shrubs, causing poor plant growth and affecting the ornamental effect. From mid-to-late May to late June each year is the peak season of white grub damage. Affected branches or plants first start from the top, with the leaves gradually turning reddish brown, then the leaf margins curling, turning yellow and drying and scorching, and finally the branches and leaves dry up and a single branch or the entire plant dies. After pulling out the dead plant, the root and stem area is found to be bitten off in a ring shape.
[Morphological characteristics] White grubs are nearly cylindrical in shape, milky white, and often curved into the letter "C" shape. The body surface is densely covered with brown fine hairs, the head is yellow-brown, and there are three pairs of thoracic legs.
[Occurrence patterns] The overwintering larvae cause greater harm to peony. After Awakening of Insects each year, the white grubs begin to move. In early April, the white grubs move from the overwintering soil layer at 30 to 50 cm to the surface soil layer at 10 to 20 cm to feed on the fleshy roots of peony. Because the wounds are prone to invasion by Fusarium, this leads to the occurrence of peony root rot. From mid-to-late May to late June, before the rainy season arrives, is the peak activity period of white grubs.
[Control methods] 1. Strengthen plant quarantine to prevent the roots of seedlings from carrying insects.
2. Treat the soil before planting peony, broadcasting 3 to 5 kg per mu of 30% carbofuran granules. If the previous crop in the peony garden was peanut or sweet potato, even more attention should be paid.
3. Organic fertilizer must be fully decomposed before use. Organic fertilizer that is not fully decomposed, especially chicken manure, very easily causes massive reproduction and large-scale outbreaks of white grubs.
4. In the early stage of the disease, drench the plants with a medicinal solution. A 1500 to 2000 times dilution of 50% phoxim emulsifiable concentrate is often used. The amount of medicinal solution per plant depends on the size of the peony plant. Generally speaking, 1 to 1.5 kg of medicinal solution is used for 1- to 2-year-old small seedlings, and 2 to 2.5 kg for 3- to 5-year-old seedlings. Before drenching, dig a small hole at the base of the peony so that the medicinal solution concentrates in the root soil.
5. In autumn, after white grubs become adult scarab beetles, use the adults' phototaxis and black light lamps to trap and kill them, so as to reduce the population density of white grubs in the soil the following year.
6. Prevention is the most active and effective measure. March to April and September to October each year are the periods when white grubs begin to move and the larvae grow; at this time, root drenching has the best effect. If control is done properly in both spring and autumn within one year, it can ensure that there will be no large-scale outbreak of white grub damage in the following 2 to 3 years.