How to control powdery mildew of Calendula

Harmful plant: calendula (calendula ofeinalis l.).

Distribution and damage: the disease is common in Hebei, Liaoning, Yunnan and other places, and the damage is serious.

Symptoms: after the leaves and stems are infected, the leaves appear 0.5-1.2 mm powdery round spots, irregular distribution, and then throughout the whole leaf, so that the leaf surface is covered with a layer of white powder. The stems are also covered with white powder, and the stems and leaves of seriously diseased plants turn yellow and even die.

Pathogen: the pathogen is powdery mildew of Compositae. The mycelium-like leaves are two-sided, and a few leaves are dorsal. The meristem is barrel-shaped to cylindrical. The ascomycete is oblate. Dark thirst. The parietal cells are irregular and polygonal. There are accessory filaments ii-85 root, mostly 18-40,-like unbranched. Most of the thickness is uneven. Septate, dark brown. The ascus is ovate, rectangular to oval in shape, 24 in shape, mostly 10 or 20 stipitate or a few subsessile. The ascus is ovate, rectangular round to ovate, with yellowish eggs,-2, 3, and rarely 4.

Disease regularity: the pathogen overwintered with ascomycetes (closed cysts) or mycelia in diseased tissues, and ascospores and conidia were mainly transmitted by wind and rain. The disease is serious when the climate is dry and the temperature is 17-25 degrees Celsius.

Prevention and treatment: diseased plants should be removed and burned centrally in order to reduce the source of infection. Strengthen management, pay attention to ventilation and light transmission, apply less nitrogen fertilizer, increase phosphorus and potassium fertilizer, and control humidity. Don't plant too closely. At the initial stage of the disease, 15% Tingning wet powder 800-1000 times, or 20% antimycin 120 times, or 50% sulfur suspension 300 times.

Injured condition of Calendula

Prevention and treatment of powdery mildew of Calendula

First, the harmful symptoms: the primary round white powder spot on the leaf surface, the gray-white powder layer on both sides of the expanded leaf and the stem, and the sparse black-brown spots in the later stage of the disease, that is, the closed capsule of the pathogen. If the disease is serious, the growth of the plant is stagnant and the leaves are yellowed and withered.

2. Morphological characteristics of pathogens: the pathogen is ascomycetes of Erysiphe cichoracearum DC. The hyphae crawl on both sides of the host leaves and use haustorium to extend into human epidermal cells to absorb nutrients. Short stalks are produced from the hyphae, the stem ends are serially conidia, and the conidia are oval in size, 30-40X18-25 (um). In the later stage of the disease, there were sparse black-brown spots, that is, the closed cysts of the pathogen were 85-114um in diameter, with accessory filaments on the shell, 6-21 endophytic ascomycetes, oval-shaped, 44-107X 23-59 (um), and 2 endophytic ascospores of 19-38X11-22 (um).

Third, the characteristics of the disease: it can occur all the year round in the south, there is no obvious overwintering period, warm and humid, foggy or dewy in early spring in February and March. In the cold region of the north, the closed capsule overwintered with the diseased remains on the soil surface. In the following year, when the conditions were suitable, the ascospores were produced for primary infection, and the conidia on the disease spot were transmitted by airflow for re-infection.

Fourth, epidemic trends: lack of soil fertility or partial application of nitrogen fertilizer in production, shade between plants, poor drainage, easy to develop the disease.

5. Prevention and control methods:

The main results are as follows: (1) careful maintenance, pay attention to clear ditches and drainage, and reduce the humidity in the field. Increase the application of phosphorus and potassium fertilizer and avoid partial application of nitrogen fertilizer or lack of fertilizer.

(2) spray 25% triadimefon wettable powder 1000-1500 times or 50% sulfur suspension 300 times in time at the initial stage of the disease. In addition, 2% agricultural antibiotic 120 water agent or 150-200x solution of Bo-10 can be sprayed, once every 10-15 days depending on the disease, for a total of 2-3 times.

(3) 7000 times EC of 40% Fuxing EC can be used in areas with severe disease or drug resistance, which has a long duration and excellent control effect.

6. Commonly used agents: 25% triadimefon wettable powder 50% sulfur suspension 2% agricultural anti-120 water agent 40% Fuxing EC

Calendula powdery mildew

Hebei, Liaoning, Beijing, Shanghai, Jiangsu and other places.

[symptoms] both leaves and stems can be damaged. In the early stage, white powdery spots appeared on the positive and negative tolerance surfaces of the leaves; after the spread of the disease, the leaves were covered with a layer of white powder, and the stems were also covered with a layer of white powder; in the later stage, there were sparse black-brown spots, that is, the closed cysts of the bacteria. If the disease is serious, the growth of the plant is stagnant and the leaves are yellowed and withered.

[pathogen] the pathogen is a fungus, Erysiphe cichoracearum, whose closed capsule is oblate, and the hyphae prostrate on both sides of the host leaf. Short stalks are produced from the hyphae, the stem ends are serially conidia, and the conidia are oval in size, 30-40X18-25 (um). In the later stage of the disease, there were sparse black-brown spots, that is, the closed cysts of the pathogen were 85-114um in diameter, with accessory filaments on the shell, 6-21 endophytic ascomycetes, oval-shaped, 44-107X 23-59 (um), and 2 endophytic ascospores of 19-38X11-22 (um). Only conidia were found in Shanghai.

[characteristics of the disease] the pathogen overwintered in the diseased tissues of the injured leaves and stems in closed cysts or hyphae. The pathogen was mainly transmitted by wind and rain. When the temperature was 17-25 ℃ and the climate was dry, the disease was serious. It can occur all the year round in the south, and there is no obvious overwintering period. it is easy to develop warm and humid, foggy or dewy in early spring in February and March. In the cold region of the north, the closed capsule overwintered with the diseased remains on the soil surface. In the following year, when the conditions were suitable, the ascospores were produced for primary infection, and the conidia on the disease spot were transmitted by airflow for re-infection.

[incidence regularity] the pathogen overwintered on the diseased tissue of stems and leaves in closed cysts or hyphae, and the host range of the pathogen was wide, which could harm other Compositae flowers.

[epidemic dynamics] the disease is easy to occur due to lack of soil fertility or partial application of nitrogen fertilizer, shade among plants and poor drainage.

[prevention and control methods]

(1) Horticultural control: careful maintenance, pay attention to ditch drainage, reduce the humidity in the field. Increase the application of phosphorus and potassium fertilizer and avoid partial application of nitrogen fertilizer or lack of fertilizer. Remove the pathogen and do not continue cropping.

(2) Chemical control: choose 70% methyl topiramate 1500 times, or 20% trimethoprim 3000 times, or 12.5% uniconazole 3000 times, spray once every 10 to 15 days, 2 times for 3 times. Or 20% antimycin 100m / 100m 200 times liquid spray. Spray 25% triadimefon wettable powder 1000-1500 times or 50% sulfur suspension 300 times in time at the initial stage of the disease. In addition, 2% agricultural antibiotic 120 water agent or 150-200x solution of Bo-10 can be sprayed, once every 10-15 days depending on the disease, for a total of 2-3 times. Areas with severe disease or drug resistance can use 7000 times of 40% Fuxing EC, which has a long duration and excellent control effect.