Diseases and their control of roses

Black spot of rose

Symptoms

Initially, small purple-brown to brown spots will appear on the leaves, while purple to black stripes will appear on the young branches and pedicels. In severe cases, the entire leaf at the bottom of the plant will fall off, leaving only a few new leaves.

Prevention

Remove diseased leaves promptly, prune in winter, remove pathogens remaining on diseased stems, and do not water at night. When the seeds germinate in early spring, you can spray lime sulfur mixture. After germination, spray Syngenta Huile, Guoguang Leaf Disease Control or Benomyl, and you can spray once every ten days. If the disease breaks out, the frequency should be shortened to once a week.

Rose powdery mildew

Symptoms

When infected with the disease, the leaves will shrink and curl, and the surface will be covered with a white powdery layer.

Prevention

Carry out appropriate pruning, pay attention to ventilation and light, and it is best not to apply nitrogen fertilizer to keep the plant healthy. When the disease first occurs, you can spray pesticides such as oxycarboxin, Guoguang black and white disease inhibitor or methyl thiophanate, about once every week, for two or three times in a row.

Downy Mildew of Rose

Symptoms

At the beginning, irregular chlorotic spots will appear on the back of the lower leaves, and they will be covered with frosty mildew. Later, they will turn dark purple to brown, and the spots will gradually change from polygonal to burn-like.

Prevention

Pay attention to ventilation and it is best not to plant too densely. You can spray 70% Guoguang mancozeb, thiophanate-methyl and other agents once every 7 to 10 days, and spray 2-3 times in a row.

Rose rust

Symptoms

Leaf rust disease can harm the buds, leaves, branches, flowers, etc. of roses, mainly the leaves. The most obvious symptom is the appearance of powdery particles like rust.

Prevention

Once discovered, it should be removed in time. You can use Guoguang Black and White Disease, 70% Guoguang Mancozeb, and Chlorothalonil alternately.

Rose root canker

Symptoms

The disease will appear at the root collar of the plant close to the ground surface. The stem bark will fade at first, and then expand into irregular black spots with dry edges.

Prevention

The breeding environment should not be too humid. Diseased branches should be removed in time if found. You can spray agricultural streptomycin or chloramphenicol, or you can spray 43% formaldehyde 40 times solution on the surface.

Rose dieback

Symptoms

This type of disease often occurs at the wounds of pruned branches or at the grafted sites. In the early stage, there will be small purple spots, which will slowly expand and become light brown in the middle and purple-red at the edges, in an irregular shape. In the later stage, the spots will crack and produce small dark brown spots. In severe cases, the lesions will circle around the branches, and the branches above the diseased part will wither or even the entire plant will die.

Prevention

It is best to prune on a sunny day and apply sulfur powder to the cut ends. If diseased branches are found, they should be cut off immediately. It is best to spray 500-800 times diluted 75% thiophanate-methyl wettable powder.

The above is all the content about rose diseases and prevention. I hope it will be helpful to everyone.