Methods and Key Technical Points for Pest and Disease Control in Rosa omeiensis

1. Powdery Mildew

It is very likely to develop on leaves, petioles, young shoots and flower buds. Irregular powdery white spots appear on mature leaves, and then the diseased leaves slowly turn brown starting from the leaf tips or leaf margins, which ultimately causes the entire leaf to gradually dry up and fall off. If young leaves are accidentally infected, the spots gradually expand and their margins become indistinct; white powdery patches form on both the upper and lower surfaces of the young leaves, and later cover the entire leaf. The leaves also begin to turn pale gray or purplish red. If the petioles are infected, the internodes begin to shorten, the stems begin to thin, and some diseased shoots also dry up and become covered with white powder. If the flower buds are infected, the pedicels become deformed, and in severe cases the plant dies outright.

Control methods: Choose varieties resistant to powdery mildew. When pruning in winter, be sure to cut off all diseased branches and diseased buds. In the early stage of the disease, apply a little less nitrogen fertilizer and a little more phosphorus and potassium fertilizer, which can improve its disease resistance. In addition, pay attention to timely drainage after rain to prevent moisture from lingering for a long time, which can reduce the occurrence of the disease.

2. Black Spot

When the disease occurs, it generally attacks the leaves, petioles and young shoots. When the leaves first show symptoms, small purplish brown to brown spots appear on the upper surface, and after they expand they become round or irregular dark brown lesions.

Control methods: We can choose some drugs such as carbendazim or miconazole nitrate and spray them on the affected areas.

3. Anthracnose

The spots produced are generally on the leaf margins, roughly semicircular in shape. The edges of the spots are dark brown, while the centers become correspondingly brown to light brown, and afterward numerous small black dots form on the lesions. This pathogen can generally overwinter on diseased fallen leaves. In relatively warm, humid environments, the spores germinate and infect the leaves.

Control methods: Timely cleanup can be carried out in late autumn and early winter, collecting the diseased fallen leaves and burning them all together. Protection should also be strengthened, with appropriate pruning and tidying. Thin out the denser branches and leaves, keep ventilation smooth, and make sure the lower branches and leaves receive sunlight. Alternatively, using some drugs is also acceptable.