How to Treat Rose Rust? Detailed Explanation of Damage Symptoms and Control Techniques
Recently, flower growers who have planted roses are troubled by a rather vexing problem: what should be done when roses contract rust? Is there still a way to treat it? Rose rust is actually a common and frequently occurring leaf disease during the growing season, affecting the buds, leaves, young shoots, petioles, receptacles, pedicels and other parts of roses, mainly occurring on buds and leaves. Below, let's learn about the control measures for rose rust together with the editor.
I. Damage Symptoms
During the spring budding period, diseased buds are initially pale yellow with swollen bases, and within 1 to 3 layers of scales a large amount of orange-yellow powdery material grows, resembling small yellow flowers. Diseased buds cannot grow, some become curved and deformed, and they die after 15 to 20 days. After young leaves are damaged, yellow small dot-like spore containers first cluster on the upper surface of the leaves, appearing as irregular yellow diseased patches. Later, orange-yellow summer spore piles form on the underside of the leaves, and in severe cases the leaf surface is covered with spots.
In autumn, dark brown powdery winter spore piles form on the diseased patches on the underside of the leaves. After axillary buds are infected by the pathogen in autumn, most die over the winter. The affected parts of the plant often become raised or overgrow or appear deformed, and infected plants drop their leaves early and grow weakly.
II. Disease Occurrence Patterns
The rose rust pathogen mainly overwinters as mycelium in diseased buds or affected parts, or as winter spores on dead branches, diseased leaves and fallen leaves. Leaves begin to develop the disease in late April each year. Late May to early July, and late August to late September are the peak periods of disease occurrence. In early August, when the average temperature is above 27°C, the disease does not develop; at temperatures above 28°C, summer spores do not germinate. After late September, only axillary buds develop the disease. Temperature plays a key role in the epidemic of this disease, and moisture is also crucial for the germination of rust spores and summer spores; generally, spores can only germinate in the presence of free water. Therefore, in years with abundant and evenly distributed rainfall and in warm, rainy and foggy regions throughout the four seasons, the occurrence and spread of this disease are favored, while in regions with high summer temperatures or cold winters, the disease is milder.
III. Control Techniques
Application of disease-resistant varieties: Selecting rust-resistant rose varieties and disease-free mother plants is one of the important measures for controlling rose rust. Attention should be paid to promoting and applying them in production, as they play an important role in controlling rose diseases.
1. Horticultural Measures
In rose production, continuous cropping should be avoided and crop rotation should be practiced to prevent the pathogen from spreading between fields with water flow. When growing in pots, the soil should be changed in a timely manner. Choose high, dry and fertile sandy loam for planting, avoid dense planting, and keep the plants well ventilated and exposed to light. Fertilize reasonably, use nitrogen fertilizer reasonably, and use fully decomposed fertilizer to promote robust plant growth. Remove diseased residues in a timely manner to reduce sources of infection, collect diseased residues, and destroy them in a centralized manner. Inspect from late March to early April, and immediately remove and cut up any diseased buds found. Generally, the rate of diseased buds is less than 0.5%, and removal can prevent the spread of spores.
2. Chemical Control
After pruning in early spring, spray 2 to 5 degrees Baume lime sulfur mixture. Before the two peak disease periods in early April or late August, spray 1 to 2 times to control the development of the disease. During the disease period, spray 50% mancozeb 500-fold solution, 25% triadimefon wettable powder 1500-fold solution, or 0.2 to 0.4 degrees Baume lime sulfur mixture, once every 10 to 15 days, for 2 to 3 consecutive sprays, or use 20% carboxin emulsifiable concentrate 800-fold solution, once every 30 days; all can achieve relatively good control effects.
The above is all the content about the occurrence patterns and control methods of rose rust. If the roses you grow at home have also suffered this damage, then hurry to Huinong Network to learn more about how to prevent it!
Symptoms and Control of Rose Rust
Rose (scientific name: Rosa chinensis Jacq.): known as the queen of flowers, also called "yueyuehong", is an evergreen or semi-evergreen low shrub that blooms in all four seasons, generally red, or pink, occasionally white and yellow; it can be used as an ornamental plant and also as a medicinal plant, and is also called yueji. It has three natural varieties. Modern roses have diverse flower forms, including single-petaled and double-petaled, as well as elegant flower forms such as high-centered with rolled edges; their colors are brilliant and rich, not only including single colors such as red, pink, yellow and white, but also varieties with mixed colors and silver edges; most varieties are fragrant. There are many rose varieties, with nearly ten thousand in the world, and China also has more than a thousand. The rose rust pathogen damages leaves, young shoots, flowers and fruits. Symptoms on leaves and buds are the most obvious. In the early stage of the disease, small slightly raised yellow spots appear on the underside of the leaves, gradually expand, and then break through the lower epidermis to release orange-red powder, namely the pathogen's rust spore piles. They are 0.5-1.5 mm in diameter, and the outer edge of the diseased spot often has a faded ring. On the upper surface of the leaves, small orange-yellow blister spots form, namely the pathogen's spermogonia. As the disease develops, slightly polygonal larger diseased spots about 3-5 mm form on the underside of the leaves, with rusty powdery material, namely the pathogen's summer spore piles. In late autumn, brown-black powdery material also forms on the underside of the leaves, namely the pathogen's winter spore piles. When young shoots and fruits are infected, the diseased spots are noticeably raised, round or oblong.Rose rust is caused by infection by Phragmidium rosae-multiflorae, belonging to Basidiomycota, Teliomycetes, Uredinales, Pucciniaceae, Phragmidium. The pathogen produces five types of spores, namely spermatia, aeciospores, urediniospores and teliospores, while teliospores germinate to produce basidiospores. These spores all have different morphologies, functions and infection and transmission abilities.
The rose rust pathogen overwinters as mycelium or teliospores on diseased buds and diseased branches and leaves. The following year, teliospores germinate to produce basidiospores, which invade the plant and produce spermatia and aeciospores; aeciospores reinfect and produce urediniospores; urediniospores invade through stomata and are spread by wind and rain, causing repeated infections during the growing season and spreading damage. The optimum temperature for the growth and development of teliospores is 18°C, for aeciospores 10-21°C, and for urediniospores 19-27°C. Generally, with more autumn rain, the rate of diseased buds in spring is high; with more spring rain, the rate of diseased leaves is high. When summer temperatures are high or winter temperatures are low, and the cold period is long, the disease generally occurs less severely; if the four seasons are warm and there is more rain and more dew and fog in a given year, urediniospores can grow and infect year-round, and the disease occurs severely. Among varieties, the double-petaled red rose and the Gansu small-leaf rose are the most susceptible, while the Beijing single-petaled red rose, white rose, Soviet perfume rose and others are relatively resistant.
Control Methods
1. In conjunction with clearing the planting site and pruning, remove diseased branches, diseased leaves and diseased buds, sweep up fallen leaves in the field, and burn them in a centralized manner.
2. Appropriately increase the application of calcium, potassium, phosphorus and magnesium fertilizers to improve plant disease resistance.
3. During the disease period, spray 25% triadimefon 1500-fold solution, or 50% dinitrocaphene wettable powder 200-fold solution, or 75% oxycarboxin emulsifiable concentrate 3000-fold solution.
Symptoms and Control Methods of Rose Rust
Rose rust occurs in climatically suitable regions in countries around the world. It sometimes causes serious damage to greenhouse-cultivated roses. In addition to roses, the disease can also infect flowers such as rugosa roses and multiflora roses.
Pathogen
There are many species of pathogens causing rose rust; 10 species have been reported abroad, and 3 species are known in China. Among them, Phragmidium montivagum (Pers.) Schlecht. is the main pathogen, belonging to the fungal subphylum Basidiomycotina, genus Phragmidium.
Symptoms
The disease mainly damages leaves, petioles and buds, and can also damage shoots, calyces and fruits. In spring, the affected upper leaf surface produces very small orange-yellow blisters, which are the pathogen's spermogonia; slightly later, slightly raised orange-yellow spots appear on the underside of the leaves, namely aecia, which after maturing break through the epidermis and release orange-red rust spore piles, and the outer edge of the diseased spot often has a faded ring. Soon afterward, orange-yellow summer spore powder piles also form on the underside of diseased leaves. In the later part of the growing season, brown to black small winter spore powder piles form at the sites where summer spore piles had formed. The affected parts of the plant often become raised or overgrow or appear deformed, and infected plants drop their leaves early and decline in growth.
Occurrence Patterns
The pathogen overwinters in diseased buds or affected parts, or as teliospores on dead branches, diseased leaves and fallen leaves. This pathogen is an autoecious rust fungus, that is, all 5 stages in its life cycle occur on the same host. The following spring, teliospores germinate to produce basidiospores, and basidiospores germinate and invade new leaves to cause primary infection. During the growing season, urediniospores are spread by wind and rain and invade through stomata, and multiple reinfections can occur.
Epidemic Characteristics
Temperature plays a key role in the epidemic of this disease. The optimum temperature for teliospore germination is about 18°C, and at 25°C basidiospores are difficult to form. The optimum temperature for aeciospore germination is 15-21°C. Although most urediniospores can germinate at 9-25°C, the optimum temperature for germination is 18-21°C. Moisture is also crucial for the germination of aeciospores and urediniospores; generally, spores can only germinate in the presence of free water. Therefore, warm rainy and foggy regions throughout the four seasons favor the occurrence and epidemic of this disease, while it occurs more mildly in regions with high summer temperatures or cold winters.
Control Methods
1. Reduce sources of infection: in conjunction with pruning, collect diseased residues and destroy them in a centralized manner.
2. Do not plant diseased seedlings, and use nitrogen fertilizer reasonably.
3. Chemical control: after pruning in early spring, spray 2-5 degrees Baume lime sulfur mixture. During the disease period, spray 50% mancozeb 500-fold solution, or 97% sodium dinitro-o-cresolate 250-300-fold solution, or 0.2-0.4 degrees Baume lime sulfur mixture, or 50% dinitrocaphene wettable powder 200-fold solution, once every 10-15 days, for 2-3 sprays. Or use 20% carboxin emulsifiable concentrate 800-fold solution, once every 30 days.