Have you ever noticed that the leaves of rose plants often have black or brown spots (see pictures below)? The leaves may also be yellow or very slightly green around the dark spots. This condition is called sooty mold (also called black spot disease) or in scientific terminology asDiplocarpon rosedesignated. Any gardener who has ever grown roses has seen black spot disease up close - too close and too often, because most roses are affected by this disease. You can first combat them with homemade black spot sprays before resorting to a chemical fungicide or extreme pruning. Discover helpful tips and good home remedies for sooty mold below!
As the name suggests, the first signs of black spot disease are irregularly shaped spots up to 1.5 cm in diameter, especially on the top of the leaves. Ifthe disease developsworsens, the leaves begin to yellow and eventually fall off the plant prematurely, predominantly from the bottom up. Over time, the entire plant can become defoliated and the canes can also become infected.
What causes star sooty mold on roses?
The main cause of black spot on roses is a fungal infection: it is the most serious disease for rose bushes. The fungus, Diplocarpon rosae, weakensthe vitality of the plant, by attacking the leaves and gradually killing the plant.
Star sooty mold occurs mainly at the beginning of spring and in very few cases in winter. By midsummer, many roses have already lost their leaves. Like most fungal diseases, black spot is favored by moist, wet environments and cool temperatures - conditions most likely to occur early in the growing season. If this disease is not controlled, it canhinder flower formation. Black sooty mold usually does not cause plant death in the first year or two, but if it continues unchecked, your roses will become more susceptible to other diseases and unable to survive harsh winters. You may notice that star sooty mold produces spores that are carried by the wind to other leaves or plants, so as the spores spread, other rose bushes will also be affected.
Yellow leaves and brown spots – prevent sooty mold
Perhaps the most common phrase you hear when discussing plant health with a botanist is: “Prevention is better than cure.”
Use sunlight:Choosing a location with maximum sunlight per day (we're talking about 6-8 hours) will improve the roses' resilience and vitality. Therebrown spots and yellowLeaves caused by moisture, constant sunlight and warmth prevent the formation of fumes, eliminating the risk of infection or other fungal diseases.
Water enough:When watering, be careful not to get the top of the leaves wet, as moisture could accumulate there and never evaporate. Rose plants do not require much watering, so a small watering at ground level is more than sufficient.
Treat star sooty mold with natural remedies
Once you have noticed the symptoms of black spot, there are some treatment options you can use to save your roses.
Remove the infestation
Cutting back the yellow leaves on the canes will reduce the risk of the disease spreading. If you notice diseased shoots before the leaves appear,remove theseimmediately from your rose plant. Try not to throw the infected leaves and stems into the compost. Even a slight breeze could blow the fungal spores back into your rose bushes.
Healing with baking soda and vinegar
Baking soda (baking soda) is a popular home remedy for treating sooty mold. The typical mixture is 1 heaped tablespoon of baking soda to 1 liter of water. Most gardeners recommend adding a little liquid soap to help the mixture adhere better to the plant.
Alternatively, you can make a mixture at home of 1 tablespoon of white vinegar, 1 tablespoon of baking soda and 1 tablespoon of liquid soap mixed with 4 liters of water.
Neem oil for brown spots
Neem oil is a biological pesticide and is cold pressed from the seeds of the neem tree. The organic oil penetrates the rose plant's system and protects it from the inside out. Just be careful not to spray the oil on the leaves in the hot sun as it will burn the foliage.
Fight star sooty mold with milk
Milk has been shown to be effective against fungal diseases in some cases, particularly black mold. Mix 1 part milk and 2 parts water in a spray bottle and you're good to go. Moisten both the top and bottom of the leaves and remove any diseased leaves or other debris underneath the rose. Use the product once a week or every two weeks.
Ideally, you should apply the remedy before you notice yellow leaves and brown spots. This method is more of a prevention strategy to help prevent the spread of soot.
