Prevention and control techniques of black spot of rose

Rose black spot occurs in many places. The disease harms the rose, makes the leaves withered and yellow, falls early, causes the second leaf of the rose in the same year, weakens the growth potential of the plant and reduces the yield of cut flowers.

First, symptoms

Rose black spot mainly affects leaves, but also affects petioles, veins, shoots and other parts. In the early stage of the disease, small brown spots appeared on the front of the leaves, which gradually expanded into round, round or irregular spots. The lesion is 2-12 mm in diameter, dark purple and radiating at the edge. In the later stage, the central tissue of the lesion turned gray, with many black dots scattered on it. In some varieties, the disease spot tissue turns yellow, and the disease spot connects with each other, so that the leaves turn yellow and fall off.

Second, the law of the disease.

The overwintering mode of pathogens varies with planting methods. Rose cultivated in the open field overwintered with pathogenic mycelium on bud scales, leaf scars and litter, while in protected cultivation rose overwintered with conidia and mycelium in the diseased part. The way of infringement is to spread by Rain Water and irrigation water splashing. After the conidia germinated, the epidermis could directly invade the plant tissue, the incubation period was 3-4 days under suitable conditions, and the fruiting body was produced after 15 days of inoculation.

1. The relationship between disease and climate

Rose cultivated in the open field, generally speaking, the disease occurs early in the year when the rainy season comes early, and when the rainfall is large, the disease is serious. When the rose cultivated in greenhouse is below 25 ℃, the higher the air relative humidity is, the more favorable the disease is.

2. The relationship between disease and cultivation management

For cut rose cultivation, the density should be 35 cm apart, too dense and susceptible to disease, and too sparse would lead to poor greenhouse utilization and economic benefits. In open rose cultivation, the row spacing should be determined according to the use and seedling age, and it is suitable for uncrowded, good ventilation and light transmission. In fertilization, we should pay attention to the reasonable collocation of nitrogen, phosphorus and potassium fertilizer, and avoid partial application of nitrogen fertilizer.

3. The relationship between disease and variety

All the common varieties of rose can be infected by black spot, but there are significant differences in disease resistance among varieties. Summary of cultivation experience: peace, Elizabeth, black thousand layer, David, Thompson and other varieties are highly resistant varieties.

4. The relationship between disease and leaf age.

The results showed that the old leaves were more resistant, the new leaves were susceptible to disease, and the leaves were most susceptible to disease when they were unfolded for 6-14 days.

III. Prevention and control measures

1. Reduce the source of disease

Withered branches and leaves should be thoroughly removed in autumn, and cut off disease and insect branches, over-dense branches and cross branches in combination with winter cutting, and concentrated burning. 1% copper sulfate solution can be sprayed to kill the source of overwintering bacteria on the diseased remains during the dormant period from November to February before the defoliation of leaves in winter to the germination of new buds in the following spring.

2. Scientific management

The application of fertilizer and water should be scientific and reasonable, adding phosphorus and potassium fertilizer, suitable nitrogen fertilizer and more organic fertilizer to enhance the disease resistance of the plant. It is best to use drip irrigation or watering along the edge of the basin, avoid sprinkler irrigation, watering time to sunny morning is better, in order to keep the leaves dry. Planting or potted flowers in a large area should not be too dense, so as to facilitate ventilation and light transmission and reduce the occurrence of diseases.

3. Chemical control

At the initial stage of the disease, 80% Dysen zinc wettable powder was sprayed with 1000-fold solution of 70% methyl topiramate wettable powder, or 50% carbendazim wettable powder. The control effect was better when it was sprayed once every 10 days and continuously for 3 times. In order to prevent pathogenic bacteria from producing cattle drug resistance, it is better to use agents alternately.