Prevention and Treatment of Rose Black Spot and Powdery Mildew

This is day 838 of Lan Yao's daily original article

This article is one of Lan Yao's original theories

Excerpt from the "Three-Step Rose Growing Method" series

In yesterday's article, Lan Yao introduced the rose stem sawfly. Actually, in this season, besides the high incidence of the rose stem sawfly, the two major diseases of roses are also in their budding stage, namely black spot and powdery mildew.

Black spot and powdery mildew are extremely harmful to roses, and their incidence rate is very high, especially in spring, in seasons with high air humidity and high temperatures, rose black spot and powdery mildew easily break out.

Today Lan Yao will talk about the prevention and treatment of rose black spot and powdery mildew.What is black spot?

Rose black spot is caused by fungal infection, a disease in which black spots appear on rose leaves, petioles, leaf tips, young tender branches and pedicels. It mainly harms rose leaves, causing black spots on the leaves, which turn yellow and eventually fall off.Characteristics of black spot:

Black spot mainly occurs when temperatures are relatively high and there is more rain, with high incidence from June to September, and it also easily occurs when there is a lot of rain in spring. Rose leaves infected with black spot develop black spots, and as it develops further the leaves turn yellow and then fall off. If roses infected with black spot are left untreated, the leaves will soon drop completely.Prevention and control measures for black spot:

Prevention and control of black spot is relatively simple. Zineb can be used for prevention. If you do not want to use chemicals for prevention, you can use the method of covering with plastic film to prevent the production of black spot fungal spores.

If roses are found to be infected with black spot, measures should be taken promptly: remove the infected leaves and spray with fungicides such as thiophanate-methyl and mancozeb for treatment. Do not leave them untreated and let them develop, or all the rose leaves will fall off and the plant will most likely die in the end.What is powdery mildew?

Powdery mildew, like black spot, is a fungal disease. After roses are infected with powdery mildew, white powder appears on the rose leaf surface, tender tips, flower buds, etc. In severe cases the leaves turn yellow and fall off, affecting the normal growth of the rose and causing the flower buds to wither.Characteristics of powdery mildew:

Powdery mildew tends to occur from April to June and from September to October, in seasons with high air humidity. In the early stage of the disease, the edges of rose leaves curl, and when you turn them over you can see white powdery substance on the back, which then gradually spreads to the stems and flower buds, where a layer of white powdery substance can be seen covering the stems and flower buds.Prevention and control measures for powdery mildew:

The occurrence of powdery mildew is mainly due to excessively high air humidity, so keeping the environment ventilated and relatively dry can effectively prevent powdery mildew. Before the disease occurs, zineb can be used for prevention. If infection with powdery mildew is found, first cut off the infected leaves, then spray with myclobutanil.

Lan Yao's own summary of medication use is that lime sulfur mixture has a relatively good effect on powdery mildew, it just smells a bit strong. Flower friends growing outdoors can first use lime sulfur mixture for treatment. When treating with myclobutanil or kresoxim-methyl, zineb or a small amount of soapy water should be added to increase the spreading property of the solution.

Because ordinary agents do not easily adhere to the fungal spores of powdery mildew, the treatment effect is relatively poor. Adding soapy water can increase the spreading property of the solution, making it easy to adhere to the powdery mildew fungus, for a better sterilizing effect.

Besides black spot and powdery mildew, rose downy mildew is also a disease with high incidence in spring.Characteristics of downy mildew: When downy mildew occurs, smeared brown spots appear on rose leaves. In the early stage of the disease, water-soaked scars appear, which need attention.

Downy mildew, black spot and powdery mildew all belong to fungal diseases, and the medications used should all be fungal medications. If bacterial disease medications are used to treat fungal diseases, the effect is minimal, and this must be kept firmly in mind.

Besides these three major diseases, there are many other common rose diseases. What other rose diseases would you like to know about? Feel free to leave a message for Lan Yao below. In tomorrow's article, Lan Yao will further discuss the prevention and treatment of common rose diseases.

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