Disease and insect pest control of planting zinnia

White star disease of hundred-day grass

Symptoms: disease on the leaves. A small dark brown spot at birth, followed by a dark brown surrounding spot with a gray-white center, 2mm in diameter. Most of the disease occurred on the lower leaves, and the leaves curled and withered in severe cases. There is a dark green mildew on the surface of the lesion.

The pathogen CercosporazinniaeEllisetMartin is Cercospora chrysanthemum, which belongs to the subphylum of fungal semisinospora.

The way of transmission is that the mycelium overwinters on seeds or diseased bodies, and it can also overwinter on diseased plants cultivated in greenhouse, which becomes the source of primary infection. Germs on disease spots can also be spread through wind, rain and gardening operations.

The disease condition of zinnia is beneficial to the occurrence of the disease under the condition of high temperature and humidity. The suitable temperature for the onset of the disease is 22-28 ℃ and the relative humidity is more than 85%. However, in the case of high temperature and drought and condensation at night, it is also easy to occur. In addition, lack of fertilizer, lack of water, or flood irrigation, poor growth and so on are easy to develop.

Control methods of zinnia

1. Strengthen management, apply enough fertilizer, cultivate strong seedlings, protect against rain and shade, and water at the right time after planting to prevent flooding. Strengthen the ventilation of the shed and reduce the humidity. Remove the disabled body in time.

2. In the early stage of drug control, remove the diseased leaves in time, and then spray immediately. Add 0.1% sulfur powder to Bordeaux solution with 1% 0.5% Bordeaux, or 500 times with 65% zinc wettable powder, or 500 times with 75% chlorothalonil wettable powder, or 800 times with 50% dichlorothalonium. 1000 times.

Zinnia nigra black spot

The black spot of hundred-day grass is also known as brown spot. It happens all over the country. The leaves of the infected plants turned brown and withered, and the petals shrunk, affecting ornamental.

Symptoms: leaves, stems and flowers can be harmed by the disease. Small black-brown spots appeared on the leaves at first, and soon expanded into large spots of regular shape, with a diameter of 2 mm ~ 10 mm, reddish brown. With the expansion and increase of spots, the whole leaf became brown and withered. The disease on the stem begins at the base of the petiole, develops longitudinally and becomes a long dark brown spot. The symptoms of flower organ damage were similar to those of leaves, and soon the petals shrunk and dried up. In the seedling stage, when the base of the stem is damaged, a dark brown central sunken ulcer spot is formed, and the disease spot gradually surrounds the stem, making the seedling show the symptom of standing blight.

The pathogen is fungus Alternaria AlternariazinniaePa-pe.

Infection route: this pathogen overwintered on diseased leaves, diseased stems and other remnants. Those with disease may also be the source of primary infection. The pathogen is spread by wind and rain and can be infected in the whole growth process of zinnia. Especially in the high-temperature and humid climate, the disease is the most serious.

Prevention and control methods:

1. Choose the area with good arrangement for planting. Planting density should be appropriate. Avoid continuous cropping. The seeds should be disinfected before sowing (inoculated with 1000 times of carbendazim wettable powder for 10 minutes). After autumn, diseased leaves and stems were destroyed to eliminate the source of infection in the coming year. Leave seeds from healthy mother plants that are disease-free.

2. Spray with 5000 times of 50% mancozeb or mancozeb or 80% Xinwansheng right wet powder. When spraying, you should pay special attention to spraying evenly on the back surface of the leaves.

Zinnia mosaic disease (CMV)

It occurs all over the country, which often causes plant dwarfism, degradation and ornamental decline.

Symptoms: the upper part of the leaf was slightly mottled at the beginning of the disease, and later became deep and shallow green mottle disease. The symptoms are more obvious in the new leaves.

Pathogen: the main virus causing zinnia mosaic disease is cucumber mosaic virus CMV.

Route of transmission: this virus disease can be transmitted by a variety of aphids, the host range of cucumber mosaic virus is very wide, and the hundred-day grass growing season is the active period of aphids, there is a great correlation between aphids and the occurrence of the disease.

Control methods: the control of aphid and disease has a certain control effect on the mosaic disease of zinnia. In addition, attention should be paid to sanitary management in the field, eradication of diseased plants and removal of other hosts of CMV in order to reduce the source of infection.