Spring is a gardener's favourite time of year, but this one unsightly disease can quickly take over much-loved rose gardens
Lifestyle Katherine McPhillips and Alexandra Whiddon Audience Writer 03:30, 20 Apr 2025
There’s no denying that roses need more care than other plants. However, gardeners are urged to pay close attention to their leaves, especially in the next couple of weeks, to ensure they don’t get infected by black spot disease.
The April showers create the perfect warm and moist environment for the black spot disease to flourish, and once it takes over, it’s incredibly hard to get rid of. Black spot disease is a fungal infection that mostly affects roses.
The unsightly disease, caused by the fungus Diplocarpon rose, leads to yellowing and premature leaf drop. Unfortunately, the disease weakens the plant, making it more susceptible to other stunted growth and reducing its bloom cycle.
Symptoms often start with small black and dark spots on the upper surface of the rose leaves. The spots often quickly grow and are surrounded by a yellow halo, ultimately leading the leaves to drop prematurely.
If left untreated, the roses will weaken over time as their energy will be spent fighting the infection. The weak roses are more prone to pests and other diseases that can enter the garden.
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However, gardeners are told this simple hack can help prevent the disease. If roses are pruned annually, they will have more airflow, which will help them dry and stop the disease spores from spreading.
Additionally, it’s important to only water the flowers close to the base to avoid any moisture on the leaves, making the plant much more vulnerable to infection. However, if roses do become infected, there is a unique solution using a common kitchen ingredient you most likely already have.
Kevin Lee Jacobs, gardener and founder of A Garden for the House , explains that cow's milk is the “smartest” way to control black spot disease. Kevin says: “A spray composed of one part milk and two parts water is the best answer to the disease. When applied weekly, the solution controls blackspot as well as any synthetic fungicide, including Chlorothalonil.”
While there’s no denying that using cow’s milk in the garden might sound a little odd, there’s actually some pretty impressive science behind it. The natural proteins and enzymes found in dairy have unique antifungal properties which can, weirdly enough, kill spores.
The milk works best when exposed to direct sunlight, as it can form an environment less hospitable to fungi. The liquid then creates a thin layer that will stop the spores from sticking to the plant.
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Kevin explains: “Spraying is work, but it isn’t hard work. Just be sure to wet both the top and bottom of the leaves. Pick up any fallen leaves, too. Otherwise, the spores of the fungus can splash back onto the rose during a rain storm.”
This unique milk solution has been proven to work incredibly well in eliminating black disease infection. So, try this natural alternative next time you see your roses break out with little dark spots. You might just be pleased with the results.
