Detailed Guide to Identifying and Controlling Damping-Off Disease in Crown Daisy
Crown daisy (Glebionis coronaria) refers to the stems and leaves of the Asteraceae plant crown daisy. Also known as ponghao, chrysanthemum greens, hao cai, tonghao cai, yi cai (goose vegetable) and ai cai, it is an annual or biennial herbaceous plant of the genus Chrysanthemum. The roots, stems, leaves and flowers of crown daisy can all be used as medicinal material, with effects of purifying the blood, nourishing the heart, lowering blood pressure, moistening the lungs and clearing phlegm. Crown daisy has a distinctive aroma, and its seedlings or tender stems and leaves are eaten stir-fried, in cold dishes or in soups. In Europe, crown daisy is used as a flowerbed ornamental.
Crown daisy is a shallow-rooted vegetable, with its root system distributed in the topsoil layer. The stem is round, green and has a hao aroma. The leaves are elongated, with wavy or deeply lobed margins and thick leaf flesh. The flower head is a capitulum with yellow flowers, and the achene is brown. The seed used in cultivation, botanically called an achene, has angular ridges and an average thousand-grain weight of 1.85 g. Crown daisy prefers cool conditions and cannot tolerate high temperatures; its optimum growing temperature is around 20°C, growth is slow below 12°C, and growth is poor above 29°C. Crown daisy is not demanding about light and generally does better with weaker light. It is a long-day vegetable; under long-day conditions, vegetative growth cannot develop fully and the plant quickly enters reproductive growth, flowering and setting seed. Therefore, in cultivation it is best scheduled for the shorter-day spring and autumn seasons. It is not demanding about fertilizer and water conditions, but it is best not to have standing water. Crown daisy varieties are divided by leaf size into two types: large-leaf crown daisy and small-leaf crown daisy.
Crown daisy is a green vegetable we see often, and most of us enjoy eating it. Of course, because crown daisy has its own unique flavor, many people cannot eat it either. So what are the dietary therapeutic effects of crown daisy? Let us take a look together today.
Because crown daisy contains various amino acids, it has effects such as moistening the lungs and tonifying the liver, stabilizing mood and preventing memory decline. Crown daisy also contains crude fiber, which helps intestinal peristalsis, promotes defecation and thus can achieve the purpose of relieving constipation and promoting bowel movement. Crown daisy is rich in vitamins, carotene and so on; its fragrance can reduce phlegm and relieve cough. Crown daisy contains protein and relatively high amounts of mineral salts such as sodium and potassium, which can regulate water and fluid metabolism in the body and eliminate edema. Crown daisy also contains a volatile essential oil, as well as substances such as choline, and has the effects of lowering blood pressure and nourishing the brain.
Introduction to and control of damping-off disease in crown daisy
What is damping-off disease in crown daisy?
Damping-off disease in crown daisy mainly harms the tender stems of seedlings. Symptoms appear once the cotyledons unfold: the base of the seedling stem becomes light brown and water-soaked, then basal rot occurs; the seedling collapses before it has even wilted, and soon the whole plant withers and dies. At first only a disease center is seen on the seedbed, but under conditions of low temperature and high humidity it spreads rapidly, and patches of dead seedlings appear. Damping-off disease in crown daisy is caused by a fungal pathogen.
Harmful symptoms of damping-off disease in crown daisy:
It mainly harms the tender stems of seedlings. Symptoms appear once the cotyledons unfold: the base of the seedling stem becomes light brown and water-soaked, then basal rot occurs; the seedling collapses before it has even wilted, and soon the whole plant withers and dies. At first only a disease center is seen on the seedbed, but under conditions of low temperature and high humidity it spreads rapidly, and patches of dead seedlings appear.
Transmission routes and outbreak conditions of damping-off disease in crown daisy:
It overwinters in the soil as mycelium or sclerotia and can live saprophytically in the soil for 2 to 3 years. The mycelium can directly invade the host and is spread by water flow and farm tools. The optimum temperature for pathogen development is 24°C, with a maximum of 40 to 42°C and a minimum of 13 to 15°C, and a suitable pH of 3 to 9.5. Sowing too densely, failure to thin seedlings in time and excessively high temperatures easily induce the disease.
Control methods for damping-off disease in crown daisy:
1) Spray the seedlings with 7500 to 9000 times dilution of Zhibaosu or 0.1% to 0.2% potassium dihydrogen phosphate, which can enhance disease resistance.
2) Treat seeds with 40% banzhongshuang at 0.2% of seed weight.
3) Treat the seedbed or seedling tray with medicated soil. Either 40% banzhongshuang powder alone can be used, or 40% banzhongling mixed with thiram 1:1, applying 8 grams of pesticide per square meter of seedbed. The medicated soil treatment method is the same as for damping-off disease. In areas where seedling blight occurs alone, banzhongling alone has low control efficacy and must be mixed with an equal amount of thiram to be effective. Chloropicrin film mulching can also be used: after preparing the bed, place 2 to 4 mm of chloropicrin at a depth of 10 to 15 cm every 30 cm, covering with soil as you apply; after all applications are finished, cover the bed with plastic film, and sow or transplant after 12 to 15 days.
4) At the early stage of disease, spray with 20% tolclofos-methyl emulsifiable concentrate (Rizolex) at 1200 times dilution, or 5% jinggangmycin aqueous solution at 1500 times dilution, 10% lihuiling aqueous suspension at 300 times dilution, or 15% hymexazol aqueous solution at 450 times dilution; use 2 to 3 liters per square meter. When damping-off disease and seedling blight occur together, spray with 72.2% propamocarb aqueous solution at 800 times dilution plus 50% thiram wettable powder at 800 times dilution, using 2 to 3 liters per square meter. A plant growth regulator, yizailing mixture, can also be tried. Apply once every 7 to 10 days depending on disease severity, for 2 to 3 consecutive treatments.
5) Biological control. Use antagonistic microorganisms for biological control. Antagonistic bacteria Bacillus cereus cultured in Wu's pig manure compost can be used to treat soil, seeds and propagating tissue, and can control seedling blight.
6) Fruits close to the ground are prone to Rhizoctonia fruit rot; it is best to make a ring out of straw rope to prop up the fruits, or spray the above fungicides for control. In addition, 15% xiaomieling (a copper substitute preparation) aqueous solution at 600 times dilution, 45% tuJunxiao aqueous solution at 450 times dilution, or 80% xinwansheng wettable powder at 600 times dilution can also be used.
7) Use seed coating. Using seed coating agent No. 9-2, the seed coating technique uses seeds as the carrier and, with the help of a film-forming agent, coats the seed surface with efficient systemic fungicides, insecticides, trace elements, hormones and so on, quickly solidifying into a drug film that does not easily fall off. After sowing, the seeds absorb water, germinate, emerge and grow, and the active ingredients on the seed coating are gradually absorbed by the roots and conducted to all parts of the plant, providing control against pathogens, pests and mice both above and below ground. Cucumber seed coating agent No. 9-2 is effective on vegetables and cucurbits. The usage amount is 0.5% of seed weight (amount of active ingredient); converted to commercial product amount this is (0.5×100)÷20=2.5 grams≈2.5 (milliliters), that is, 2.5 ml can treat 100 grams of seeds. The commercial effective concentration is 20%.