From the symptoms of chrysanthemum plants, at the early stage of the disease, the whole plant or half plant began to wilt slightly, and with the passage of time, the wilting degree gradually increased, the leaves began to turn green and yellow, and then continued to develop, the plant growth stagnated, and the leaves withered from the tip or outer edge until the whole plant died.
when the root system of the diseased plant is pulled out, the main root turns black with white mold on it, and the fibrous roots are few, small, weak and curved. The color of fibrous roots changes from healthy white to morbid grayish brown, and the epidermis at the base of the stem begins to turn grayish brown in different shades, and the vascular bundles also turn brown, and gradually extend to the plant. Second, the cause of disease
To sum up, this is that chrysanthemum suffers from Fusarium oxysporum, which is caused by a specialized fungus infection of chrysanthemum, that is to say, this fungus belongs to chrysanthemum patent and generally does not harm other crops.
The control of chrysanthemum wilt is more difficult because of the following reasons:
1. Wrong judgment of the disease. Because the symptoms of chrysanthemum Fusarium wilt and root rot are similar, it is generally difficult for inexperienced growers to confirm from the plant performance. Although some fungicides for controlling root rot are also effective for Fusarium wilt, they are not targeted treatment after all, so the control effect is not obvious.
2. Continuous cropping is a disaster. Chrysanthemum planting with continuous cropping is generally not recommended. Once continuous cropping for more than three years, soil-borne diseases will begin to increase, and Fusarium wilt of chrysanthemum is also a kind of soil-borne diseases.
Fusarium oxysporum spores can overwinter in the soil. The longer the continuous cropping, the more germs in the soil. The germs can occur at 17-37℃, and the best temperature is 24-28℃. The germs can be spread by irrigation water, diseased soil, manual operation, etc., especially in acid soil, too much nitrogen fertilizer application, and then encounter high temperature and humidity, water accumulation after rain, or improper artificial watering methods, resulting in water quantity.
3. Prevention measures in advance are not in place. For the chrysanthemums planted with continuous cropping, or the chrysanthemums transplanted with continuous cropping (even if it is new cropping, the chrysanthemum seedlings bred with continuous cropping will also carry germs), the soil or seedlings must be disinfected before planting, and the chrysanthemum wilt can be prevented in the bud through a series of treatment measures. Three effective control techniques
1. Avoid continuous cropping for many years and maintain soil organic matter content. If the planting space is limited, and it needs to be replanted year after year, it is necessary to pay attention to the supplement of soil organic matter, and to supplement it every year, so that the content of organic matter and nutrient elements in the soil are not unbalanced and the soil pH is moderate. As the saying goes, rotten eyes attract dust and weak seedlings attract disease, and only by promoting plant health is the root of less illness.
2. It is very important to master watering skills. As potted plants are the main way to plant ornamental chrysanthemums, the planting steps are as follows: now transplant chrysanthemum seedlings on the ground, cover the flowerpot after the slow seedling period, and fill the pot with soil while the chrysanthemum seedlings grow in the flowerpot until the pot is filled with soil, and the chrysanthemums basically begin to take shape.
Because of this planting method, the common advanced irrigation measures can't be used. In hot summer, it is the critical period of chrysanthemum growth, and a large amount of water transpiration requires continuous water replenishment irrigation. If the irrigation measures are unscientific, when watering the chrysanthemum pot, it will often cause the phenomenon of excessive watering, which will lead to stagnant water and root retting. Coupled with high temperature and high humidity, it is most likely to induce Fusarium wilt, and at the same time increase the number of root retting and root retting.
Therefore, it is suggested that when watering chrysanthemums, we can sum up the rules of watering chrysanthemums and water requirements, and do not water them violently or frequently, and we should not only water them half-way for fear of watering. 3, chemical prevention and treatment of specific programs.
For the continuous cropping chrysanthemum fields, while paying attention to organic matter supplement, it is suggested that 2 grams of 25% copper acetate or 5 grams of 5% captan+1 billion spores/gram of Bacillus subtilis should be applied per mu in soil consolidation. These two formulas have obvious effects on preventing Fusarium wilt. Of course, in case of serious continuous cropping fields, other preventive measures should be combined.
For example, there is an ideal preventive measure, that is, root dipping. The commonly used formula is 62.5g/L of metalaxyl-m fludioxonil and 1ml of 11% metalaxyl-m fludioxonil-azoxystrobin suspension seed coating agent, which is mixed with 1kg of water and a little soil to make it into a thin paste (the dosage is one mu). After soaking the roots of chrysanthemum seedlings in liquid medicine, it is transplanted, and the disease prevention effect is obvious.
For chrysanthemums that have already suffered from Fusarium wilt, the healthy plants should be sprayed and the diseased plants should be irrigated at the same time, so that the effect will be better. The suggested formula is: 32.5% bensulfuron methyl 1ml+1 billion spores/g Bacillus subtilis 1g +8% captan 15g, or 7% thiophanate methyl 5g +25%.