Diseases and Pests of Rosa chinensis and Their Control

Diseases of Rosea rubra

powdery mildew

When powdery mildew breaks out on Rosea thorna, the main symptom is a sparse white powdery mold layer on both sides of the leaves, twisted leaves, young leaves turning purple-brown and dying, and when the disease is serious, the branches die, affecting the growth and appearance of the plant. The disease usually occurs in the tender shoots, leaves, petioles, etc. at the top of the branches.

The main method to prevent and control powdery mildew outbreaks on Rosa rugosa is to increase the application of phosphorus and potassium fertilizers and control nitrogen fertilizers. The second is to spray 800 times diluted 50% carbendazim wettable powder at the early stage of the disease, and spray 3-4 degrees Baume lime sulfur before germination. Other commonly used drugs include 1500 times diluted 20% triadimefon emulsifiable concentrate, applied once every 15-20 days, or 2500 times Heisha wettable powder, with the same interval as triadimefon. Fumigation cans can be used in greenhouses, using sulfur powder as the medicine.

Leaf blight

Rosea rubra sometimes suffers from leaf blight, which manifests itself as spots on the leaves that change from yellow-brown to gray-brown, with obvious or unclear purple-red edges. In the later stages, small black spots appear on the leaves, and the spots may break through.

The prevention and control method for Rosa rugosa skin color leaf blight is to spray 1000 times diluted 50% carbendazim wettable powder, or 200-300 times diluted 50% sulfur gel suspension, once every 10 days for 2-3 times in a row.

Pests of Rosea rubra

Rose sawfly

Rose sawfly appears between May and June and causes damage until July and August. The larvae feed on leaves, and the adults lay eggs on young branches, piercing the branches and causing cracks in the twigs. When the yellow rose is infested by the rose sawfly, you can spray 223 emulsion with 250-400 times water to kill the larvae. You can also manually cut off the branches with insect eggs and burn them in a concentrated manner.

Ligustrum moth

Yellow rose is also attacked by the moth, which occurs more frequently in June and July and often eats the young leaves. You can spray DDT or remove the overwintering cocoons manually.

aphid

Aphids are relatively common and often harm the tender tips of young branches of Rosa rugosa. They can be controlled by sprinkling 0.5-1.0% 666 powder or spraying wettable 666.