How to prevent and control damping-off in garland chrysanthemum? A detailed guide to practical methods

Garland chrysanthemum (Chrysanthemum coronarium L.), also known as tonghao, penghao, haocai, juhuacai, tanghao, haozigan, haozi, and tonghuacai (called ecai and yicai in places such as Fujian), is an annual or biennial herbaceous plant of the Asteraceae family, with alternate leaves that are long and pinnately lobed, and yellow or white flowers, very similar to wild chrysanthemum. The achene is ribbed, the plant is two to three chi tall, and the stems and leaves are edible when tender and can also be used medicinally.

Growth habits of garland chrysanthemum

Garland chrysanthemum is a semi-cold-tolerant vegetable with no strict light requirements, generally preferring weaker light. It is a short-day vegetable, and cool, mild conditions with soil relative humidity maintained at 70%-80% favor its growth. Under long-day conditions, vegetative growth cannot develop fully and the plant quickly enters reproductive growth, flowering and setting seed.

Geographical distribution of garland chrysanthemum

It originated in the Mediterranean and has a cultivation history of more than 900 years in China, with a wide distribution, though the cultivation area in each region of the north and south is very small. It is distributed in provinces such as Anhui, Fujian, Guangdong, Guangxi, Guangzhou, Hainan, Hebei Shijiazhuang, Hubei, Hunan, Jilin, Shandong, and Jiangsu.

How to prevent damping-off in garland chrysanthemum?

What is damping-off in garland chrysanthemum?

Damping-off in garland chrysanthemum mainly damages the roots and root crown. Initially, light brown to brown water-soaked oval lesions form on the diseased parts; after the diseased parts sink, the diseased stems gradually shrink or dry up. The diseased seedlings first become wilted and then gradually die, but the diseased plants mostly remain standing rather than falling over, which is why it is called damping-off.

Damage symptoms of damping-off in garland chrysanthemum:

Damping-off in garland chrysanthemum mainly damages the roots and root crown. Initially, light brown to brown water-soaked oval lesions form on the diseased parts; after the diseased parts sink, the diseased stems gradually shrink or dry up. The diseased seedlings first become wilted and then gradually die, but the diseased plants mostly remain standing rather than falling over, which is why it is called damping-off. Under high humidity, light brown sparse cobweb-like mold often grows on the diseased parts, and damping-off spreads slowly on seedbeds, making the above characteristics obvious.

Transmission routes and disease conditions of damping-off in garland chrysanthemum:

It overwinters in the soil as mycelium or sclerotia and can live saprophytically in the soil for 2-3 years. The mycelium can directly invade the host and spread through water flow and farm tools. The optimum temperature for pathogen development is 24°C, with a maximum of 40-42°C and a minimum of 13-15°C, and a suitable pH of 3-9.5. Sowing too densely, failure to thin seedlings in time, and excessively high temperatures easily induce the disease.

Control methods for damping-off in garland chrysanthemum:

1) Strengthen seedbed management and ventilate scientifically to prevent high temperature and high humidity conditions in the seedbed or seedling trays.

2) Spray 7500-9000 times diluted Zhibaosu or 0.1%-0.2% monopotassium phosphate during the seedling stage to enhance disease resistance.

3) Treat seeds with 40% banzhongshuang at 0.2% of seed weight.

4) Treat the seedbed or seedling trays with medicated soil. You can use 40% banzhongshuang powder alone, or mix 40% banzhongling with thiram at 1:1, applying 8 grams of pesticide per square meter of seedbed. The medicated soil treatment method is the same as for damping-off (Pythium). In areas where damping-off occurs alone, banzhongling used alone has low control efficacy and must be mixed with an equal amount of thiram to be effective. You can also use the chloropicrin film-covering method: after preparing the bed, apply 2-4 mm chloropicrin deeply at a depth of 10-15 cm every 30 cm, covering with soil as you apply, and after all applications are complete, cover the bed with plastic film, then sow and transplant after 12-15 days.

5) At the early stage of disease, spray or drench with 20% tolclofos-methyl EC (Rizolex) 1200 times dilution, or 5% jinggangmycin aqueous solution 1500 times dilution, 10% lifulling aqueous suspension 300 times dilution, or 15% hymexazol aqueous solution 450 times dilution; 2-3 liters per square meter. When damping-off (Pythium) and damping-off (Rhizoctonia) occur together, use 72.2% Previcur aqueous solution 800 times dilution plus 50% thiram wettable powder 800 times dilution for spray or drench, 2-3 liters per square meter. You can also try the plant growth regulator yizailing mixture. Depending on disease severity, apply once every 7-10 days, for 2-3 consecutive treatments.

6) Biological control. Use antagonistic microorganisms for biological control. Bacillus cereus cultured in Wu's pig manure compost can be used to treat soil, seeds, and propagating tissues, and can control damping-off.

7) Fruits close to the ground are prone to Rhizoctonia fruit rot; it is best to make rings from straw rope to prop up the melons, or spray the above fungicides for control. In addition, you can choose 15% xiaomieling (copper substitute preparation) aqueous solution 600 times dilution, 45% tujunxiao aqueous solution 450 times dilution, or 80% xinwansheng wettable powder 600 times dilution.

8) Use seed coating. Using seed coating agent No. 9-2, the seed coating technique uses seeds as the carrier, coating the seed surface with highly efficient systemic fungicides, insecticides, trace elements, hormones, etc. with the help of a film-forming agent, 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 translocated 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 (active ingredient amount), converted to commercial product amount as (0.5×100)÷20=2.5 grams≈2.5 (ml), that is, 2.5 ml can treat 100 grams of seeds. The commercial effective concentration is 20%.