Prevention and control of black spot of rose

Rose black spot, also known as brown spot, is a worldwide rose disease.

Symptom

Rose leaves, twigs and pedicels can all be damaged. The spot on the leaf is purple-brown to brown at first, and then expands into a diameter of 1. 5%. The round spot of 13 mm is black or dark brown, the edge is ciliate, but the upper edge of some varieties can also be neat and smooth. The plaque is often surrounded by a yellow halo. Under the magnifying microscope, black blister-like microsomes can be seen in the disease. The disease spot is often connected by several, and the leaves around the disease are yellowed in a large area, making the disease spot a "small island" with a green edge. Diseased leaves fall off easily, but some rose varieties do not fall off. Purple to black striped spots appear on young shoots and pedicels, slightly sunken. When the disease is serious, the lower and middle parts of the whole plant fall off, leaving only a few new leaves at the top.

Pathogen

It belongs to actinonema rose (lib.) fr. The conidia are placed under the protagonist's cytoplasmic layer and then protrude the epidermis. The size is 108 to 198 microns, and the meristematic peduncle is short and inconspicuous. The meristem is oval or fish-shaped, with a size of 18 "25 x 5" 6 microns, two-celled, small at the top and large at the bottom, with a slight constriction at the separation. The top is like a beak, often leaning to one side.

Route of infection

The hyphae overwintered on diseased branches, diseased leaves or diseased leaves, and the conidia were formed in the early spring of the following year, resulting in the harm of conidial transmission. The meristem tractor is also one of the sources of primary infection. Conidia spread harm by wind, rain and splashing water droplets, so it is easy to occur when it is rainy, foggy and dewy. According to the experiment, when there is water retained on the leaves, the spores can sprout and invade within 6 hours. Prevention and control of rose black spot, also known as brown spot, is a worldwide rose disease. Symptomatic rose leaves, twigs and pedicels can all be damaged. The spot on the leaf is purple-brown to brown at first, and then expands into a diameter of 1. 5%. The round spot of 13 mm is black or dark brown, the edge is ciliate, but the upper edge of some varieties can also be neat and smooth. The plaque is often surrounded by a yellow halo. Under the magnifying microscope, black blister-like microsomes can be seen in the disease. The disease spot is often connected by several, and the leaves around the disease are yellowed in a large area, making the disease spot a "small island" with a green edge. Diseased leaves fall off easily, but some rose varieties do not fall off. Purple to black striped spots appear on young shoots and pedicels, slightly sunken. When the disease is serious, the lower and middle parts of the whole plant fall off, leaving only a few new leaves at the top. The pathogen is Actinonema rose (Lib.) Fr. The conidia are placed under the protagonist's cytoplasmic layer and then protrude the epidermis. The size is 108 to 198 microns, and the meristematic peduncle is short and inconspicuous. The meristem is oval or fish-shaped, with a size of 18 "25 X 5" 6 microns, two-celled, small at the top and large at the bottom, with a slight constriction at the separation. The top is like a beak, often leaning to one side. In the route of infection, hyphae overwintered on diseased branches, diseased leaves or diseased fallen leaves, and conidia were formed in the early spring of the following year, resulting in conidial transmission harm. The meristem tractor is also one of the sources of primary infection. Conidia spread harm by wind, rain and splashing water droplets, so it is easy to occur when it is rainy, foggy and dewy. According to the experiment, when there is water retained on the leaves, the spores can sprout and invade within 6 hours. The suitable temperature for germination and invasion was 20 ℃, the PH value was 7 8, the incubation period was 10 11 days, and the incubation period of old leaves was 13 days. The pathogen can be repeatedly infected for many times and can occur throughout the growing season. In general, the disease is serious in the rainy season and typhoon season, and the disease spreads slowly in the hot and dry season in summer. Plants are susceptible to disease when they are weak. There were differences in disease resistance among varieties, but there were no immune varieties. Prevention and control methods: 1. Clean the fallen leaves and remove the diseased leaves at any time to reduce the source of infection. The seriously diseased plants were heavily pruned in winter to remove the overwintering pathogens on the diseased stems. 2, potted plants should not be placed too dense, it is best not to put them directly on the ground, lest the basin soil is too wet when the ground is flooded, and it is best to put it on the stepped planting platform. To improve the watering method and time, it should be poured from the edge of the basin to avoid spraying. Do not water at night, lest the leaves can not dry quickly when there is water, which is beneficial to the invasion of germs. 3. Chemical control. Spraying should begin as soon as the new leaves unfold in summer, usually once every 7 to 10 days. The agents used are 50% carbendazim wettable powder 500 times 1000 times liquid, or 75% chlorothalonil wettable powder 500 times liquid, or 80% Dysen zinc wettable powder 500 times liquid, or 1 hundred times Bordeaux solution, or 70% methyl thiophanate 1000 times liquid. After winter pruning, Baume 3-5 degree stone flow mixture can also be sprayed to eradicate germs. Prevention and control of black spot of rose

Rose black spot is a common and serious disease. It not only harms rose, but also roses and roses. It can cause a large number of yellow leaves, withered leaves and fallen leaves, affecting plant growth, flowering and ornamental. In particular, the incidence of rose placed and planted is more serious, which occurs in most parts of our country. Therefore, strengthening the prevention and treatment of the disease plays an important role.

-, harmful symptoms

The disease mainly harms leaves, as well as tender shoots, petioles, veins and buds. At the beginning of the disease, the leaves were purple-brown spots, and then gradually enlarged into round, near-round or unplanned disease spots, with a diameter of 4 to 12 mm, the disease spots were purple-brown or dark brown, and the periphery was inconspicuously radial, and in the later stage, the leaves around the disease spots turned yellow. there are small black spots on the disease spot, that is, the conidium disk of the pathogen, and when the disease spot is serious, the disease spot becomes yellow, and the lower leaves fall off early. Gradually spread upward and finally the upper leaves were lighted.

The disease spot on the tender shoot is long oval and dark purplish red. The disease spots on petioles and veins are similar to those on tender shoots. Most of the buds are purple-brown oval spots.

Cycle of infection and conditions of disease

The pathogen of black spot spends the winter on the diseased body or in the soil or on the diseased branch with hyphae as conidia. In the spring of the following year, with the rise of temperature, the bacteria latent on the diseased body or in the soil or on the diseased branches began to active. when the humidity was high, the bacteria were spread by watering and Rain Water splash, and the temperature was suitable. When there were water droplets on leaves and branches, they invaded through stomata or lenticels in 6 to lO hours, and symptoms appeared in 3 to 6 days. The incubation period is 3 to 4 days at 22 to 30 degrees Celsius and from lO to ll days. In the northern region, when the humidity is high from May to June, the leaves mostly start to infect from the lower leaves, and produce molecular spores with the expansion of the disease spot, which can spread with the wind and rain, and then infect after the expansion of the disease spot. The disease was serious from August to September, and the disease was rampant when the temperature was about 24 degrees Celsius and the relative humidity was about 98%. Warm, rainy, foggy, dewy, suitable for the disease in the muggy season after rain, dense among plants, over-dense potted plants, poor drainage, poor ventilation and light transmission and partial application of nitrogen fertilizer, the plant is weak, the leaves are large and soft, the disease is serious, and the disease degree is different among varieties.