As a rose owner, you must know how to control black spot disease. Black spot is a fungal disease characterized by the appearance of black spots on the upper side of the leaves. The disease tends to occur when temperatures are warm and humid, usually in the wet summer. Infected rose leaves will turn yellow and fall off. This disease will weaken the plant by making it more susceptible to other diseases or will expose the plant to sores the following winter. The organisms that cause black spots can spread quickly and move from one plant to another if not eradicated immediately.
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Method 1 of 3: Planting Roses Resistant to Dark Spots
Step 1. Plant roses that are resistant to black spot
Many varieties of beautiful roses are resistant to disease and fungus. Prevent black spot by not planting varieties that are susceptible to this disease. Maintenance of resistant varieties is much easier than those that are susceptible to various types of rose disease.
You can find specific lists of disease-resistant roses online, and nurseries usually have their own lists too. Types of roses vary by region, so find out what local varieties are best suited for your area
Method 2 of 3: Reducing the Risk of Dark Spots
Step 1. Choose the planting site carefully
The best tactic for preventing black spot is to plant roses in a good growing spot for the plant, but not for the fungus.
- Roses should get 6-8 hours of sunlight per day. Morning sun is best as it will dry the previous night's dew quickly.
- The planting location must have good air circulation. Plant the rose clumps well enough apart from each other for good air circulation, and prune some stems in the middle of the clump for internal circulation.
- Prepare the soil well. Make sure the soil is rich in weathered organic matter and is well drained. Compost that has been weathered will enrich the nutrient content of the soil.
Step 2. Water the roses sufficiently
Excessive moisture will stimulate the appearance of black spots. So, water carefully and don't overdo it. When the weather is cold, water once a week until the base of the plant is completely wet. When the weather is hot and dry, water more often, but don't let the leaves get wet.
- Use a soaker hose or drip irrigation system to irrigate the roots more frequently.
- Be careful when watering, black spot spores can move when you spray water. The use of a soaker hose or drip irrigation is the best option over a hose with a spray sprinkler.
- Water the roses only in the morning so that the leaves have dried up by nightfall.
Step 3. Prune regularly
Remove weak or damaged branches and leaves during periodic pruning.
Method 3 of 3: Treating Dark Spots Penyakit
Step 1. Know what you are looking for
Black spot disease has the following characteristics:
- The presence of rounded black spots with uneven edges on the leaves.
- The leaves at the bottom of the clump are usually infected first, then the disease will spread rapidly.
- The top leaves will turn yellow and fall off.
- Plants become weaker and flower less or not at all.
Step 2. Discard and place the infected leaves and branches in the trash as soon as you see any signs of black spots
This step will help prevent further fungal growth.
Immediately clean and dispose of leaves that are infected with black spots and leaves that fall to the ground in a safe manner. If infected leaves are left lying under a rosebush, fungal spores will return to the plant as soon as temperature and humidity allow in the spring
Step 3. Spray the roses every 7 to 14 days with a fungicide during the growing season
Even if the plant shows no signs of black spot infection, this spraying is an important step for good preventive maintenance. Fungicides that you can use include trifloxystrobin, Ziram, chlorothalonil, mancozeb, Thiophanate-methyl, and several others. For advice on proper spraying or powdering in your area, check directly with your local landscaping service.
Step 4. Prune rose stems that are infected with black spots before the growth period arrives
In severe cases, black spots can infect the stems of roses. Remove any infected stems as soon as you see them.
Tips
- A simple way to tell if a rose needs watering is to stick your finger as deep as possible into the soil near the base of the plant. If the soil feels dry, the roots will likely need to be watered abundantly.
- Add a spreader (adhesive, leveling, and penetrating surfactant) to the spray fungicide to make spraying on waxy rose leaves more effective.
- Black spots most often appear in early summer.
