A Detailed Guide to Common Pests and Diseases of Rose and Their Control Methods

The rose has a beautiful appearance, comes in a thousand forms, is richly fragrant, and blooms in all four seasons. In particular, it has a great many varieties and is easy to propagate and cultivate. It is praised by people as the “Queen of Flowers” and is one of the ten most famous flowers of our country. However, rose pests and diseases often cause poor growth and even death, seriously affecting its ornamental value. Now let us take a look together at the control methods for common rose pests and diseases!

Rose Powdery Mildew

[Symptoms] In the early stage, chlorotic yellow spots appear on diseased leaves, then expand and become covered with white powder. The leaves curl backward, shrink, and thicken. After the petioles and young shoots are infected, they swell slightly and bend backward. After flower buds are infected, the flower form becomes deformed. In severe cases, the leaves wither and yellow, and the plant becomes weak.

[Occurrence Pattern] The pathogen overwinters on buds, leaves, and branches, and spreads by wind. The optimum temperature for disease onset is 17-25°C. May to June and September to October are the peak periods of onset. The disease is likely to occur when there is too much nitrogen fertilizer or too little potassium fertilizer in the soil.

[Control Methods] 1. Select disease-resistant varieties. 2. Fertilize reasonably and avoid nitrogen fertilizer. 3. Remove and burn diseased leaves in early spring. 4. Prune moderately to keep the plant well ventilated and exposed to light. 5. Spray fungicides such as triadimefon and chlorothalonil before and after disease onset for control.

Rose Black Spot

[Symptoms] Rose leaves, flower stalks, and young branches can all be damaged. In the early stage, the disease spots are seed-brown to brown small dots, then expand and turn black or dark brown, often surrounded by a yellow halo. In severe cases, all the leaves on the middle and lower parts of the whole plant fall off, and branches die.

[Occurrence Pattern] The pathogen overwinters in diseased branches, leaves, or fallen leaves, and spreads by wind and rain. It is most severe after late summer. In high temperature and drought, disease expansion is slow. Weak plants are prone to the disease.

[Control Methods] 1. Remove diseased leaves promptly and heavily prune diseased plants in winter. 2. Prune often during the growing season to maintain good ventilation. 3. Fungicides such as chlorothalonil, carbendazim, zineb, and thiophanate-methyl can be used for control.

Rose Leaf Blight

[Symptoms] It occurs on rose leaves. In the early stage, yellow-green needle-point spots appear on the leaf surface. Later, the disease spots expand into round or irregular shapes with purple edges. After expansion, they merge into patches, with a clear boundary between diseased and healthy tissue. In the later stage, small black dots appear on the diseased parts, and the edges of diseased leaves look as if burned by fire.

[Occurrence Pattern] The pathogen overwinters in diseased leaves or soil, and spreads by wind and rain. Old leaves, weak branches, rainy seasons, and extensive management lead to severe onset.

[Control Methods] 1. Remove and destroy diseased leaves promptly. 2. Select disease-resistant varieties, plant at a reasonable density, and strengthen maintenance. 3. Spray 3-degree lime sulfur mixture during the dormant season. 4. Spray fungicides such as chlorothalonil before disease onset for prevention. 5. Spray fungicides such as carbendazim in the early stage of disease onset for control.

Rose Crown Gall

[Symptoms] Tumors of varying sizes and shapes appear on the roots and stems of the rose. The plant grows poorly, with short branches and leaves, yellowed and early-falling leaves, and small flowers or no flowers.

[Occurrence Pattern] The pathogen survives in the soil and spreads through water and tools. In the early stage, the galls are small, soft, and white; later they gradually enlarge, turn dark brown, have a rough and cracked surface, and become hard and lignified.

[Control Methods] For open-field planting, try not to grow continuously on the same land. Improve grafting standards, change grafting methods, reduce wounds, and avoid infection.

Rose Mosaic Virus

[Symptoms] It mainly manifests as mosaic patterns, with some showing ring spots or oak-leaf patterns, and some showing chlorotic spots, yellow veins, or dwarfing.

[Occurrence Pattern] It is a viral disease. Diseased plants used as propagation material, sap contact, and piercing-sucking pests can all spread it. Strong light and drought in summer favor symptom expression and expansion.

[Control Methods] 1. Avoid using diseased plants as propagation material. 2. Pull out and destroy diseased plants promptly when found. 3. Select disease-resistant varieties or tissue-cultured seedlings. 4. Pay attention to controlling aphids and other transmission vectors during the growing season. 5. Spray amino-oligosaccharin aqueous solution in the early stage of disease onset to inhibit virus expansion.

Rose Flower Rot

[Symptoms] It occurs on rose flowers and flower stalks. In the early stage, the disease spots are inside the base of the outer petals, appearing as fuzzy brown small spots. After expansion, the flower is covered by brown disease spots until it dries up to a yellow-brown color, and black granular material appears.

[Occurrence Pattern] The pathogen overwinters on diseased plant residues and spreads with wind and rain. It is prone to occur when growth is weak and humidity is high.

[Control Methods] 1. Select disease-resistant varieties and maintain ventilation and light penetration. 2. Spray fungicides such as lime sulfur mixture, anilazine, and carbendazim for control.

Rose Citrus Blackfly

[Occurrence Pattern] It occurs 4 generations a year, reaching peak occurrence in late May, late July, late August, and late September to early October respectively. It overwinters as mature larvae on the underside of leaves, causing leaf yellowing.

[Control Methods] 1. Remove dead leaves and weeds in winter to eliminate overwintering adults. 2. During the occurrence period, use fungicides such as crystalline trichlorfon, omethoate, dichlorvos, and fenitrothion for control.

Rose Aphids

[Occurrence Pattern] It occurs 10-30 generations a year, overwintering as eggs on branch tips, bud axils, and bark cracks. It begins to cause damage in mid-March, with the most serious damage in April and May.

[Control Methods] 1. Cut off branches with eggs during winter pruning. 2. Use yellow sticky boards to trap and stick winged aphids. 3. In the early hatching period and before egg laying, spray pesticides such as imidacloprid and deltamethrin for control. 3. In the early hatching period and before egg laying, spray pesticides such as imidacloprid and deltamethrin for control.

Rose Scale Insects

[Occurrence Pattern] It occurs 1-4 generations a year, overwintering as females in waxy shells. It can parasitize branches and leaves, causing tree decline and poor growth, and in severe cases the whole plant dies. Severe occurrence happens when canopy density is high and ventilation and light penetration are poor.

[Control Methods] 1. Manually scrape off the insects and waxy shells on dry branches. 2. Strengthen management, prune appropriately, increase ventilation and light penetration, and reduce the probability of occurrence. 3. Cut off and destroy infested branches promptly. 4. In the early hatching period of nymphs, spray chemical pesticides such as huabao, imidacloprid, and jiemanling for control. 5. Apply systemic pesticides such as carbofuran in a ring trench around the roots for control.

Rose Yellow-Breasted Thrips

[Occurrence Pattern] It occurs about 10 generations a year. Adults and nymphs hide inside flowers to cause damage, and eggs are half-buried under the epidermis of petals and stamens. It has a mixed diet. High temperature and drought favor its occurrence, while rainy and strong-wind conditions are unfavorable to this pest.

[Control Methods] 1. Remove dead branches and weeds in the infested area and burn them on site. 2. Spray pesticides such as imidacloprid for control. 3. Bury and apply pesticides such as carbofuran and aldicarb granules for control.

Common Pests and Diseases of Spring Flowers and Their Control Methods

Control of Common Pests and Diseases of Rose