How to Treat Blackspot With a Natural Organic Solution
Blackspot is probably the rose disease most gardeners notice first. It usually starts as dark, rounded spots on the leaves, often with yellowing around the affected area. As it spreads, the leaves may turn yellow and drop from the plant.
A few spotted leaves are not the end of the world, but a bad case of blackspot can leave a rose looking almost bare. If the plant keeps losing its leaves, it has less energy to grow strongly and produce flowers.
Blackspot is one of the diseases that is incredibly difficult to get rid of. Year after year, you think you have it whipped, and back it comes. But we have a natural organic solution that works as well as (if not better than) those traditional toxic remedies.
A few spotted leaves are not the end of the world, but a bad case of blackspot can leave a rose looking almost bare. If the plant keeps losing its leaves, it has less energy to grow strongly and produce flowers.
Blackspot is one of those rose problems I try to manage early, rather than waiting until the whole bush is covered.
Why Blackspot Spreads
Blackspot is a fungal disease, and it loves moisture. It spreads more easily when leaves stay wet for long periods, especially in warm, damp, or humid weather.
Water splashing from infected leaves or fallen foliage can move spores onto healthy growth. That is why overhead watering, crowded planting, and poor air movement can all make blackspot worse.
I try to water roses at the base where possible, and I avoid wetting the foliage late in the day. If leaves are going to get wet, it is better for that to happen early enough that they can dry before night.
How To Recognize Blackspot
This starts, as the name would suggest ,with black spots on the leaves. As the spots get bigger, they develop a yellow halo around them, the leaf begins to wither, and eventually falls off. A bad infestation can see a plant totally stripped of foliage. The culprit is a fungus, Diplocarpon Rosae, and the spores from this can remain in the ground and reinfect the bush year after year.
Prevention:
The first step towards cutting down on the blackspot infestation, is to ensure that infected leaves are removed from the plant. Also, as it can remain dormant in the ground, pick up any dropped leaves and burn them (do not compost them!). The overall plant health plays a role as well, and a regular application of sulphate of potash will help control blackspot.
Remember that blackspot thrives in humid and/or damp conditions, so keep your roses well thnned out in the center to aid air circulation, and try to avoid watering the foliage. Instead, water around the base of the plant.
Treatment:
There are plenty of anti fungal sprays available for blackpot, just ask in your local garden center. However, natural and organic treamtments can work just as well, if not better than those toxic fungicides.
Milk:
Mix 1 part milk to 2 parts water and spray the bush, gettingboth sides of the leaves. Do this weekly. It really does work!
Bicarbonate of Soda:
2 teaspoons per 5 liters of water, mix in a little dishwashing liquid to help it stick to the foliage. As with the milk solution, spray weekly during the peak blackspot season.
Sometimes, no matter what you do, nothing seems to work. There will often be a bush or two in your garden that comes out with bad blackspot year after year. Unless you have sentimental reasons for keeping it, then just replacing it with a more disease resistant variety makes sense. But for the majority of your garden, vigilance with picking off infected leaves, picking up the fallen ones and regular applications of either milk or bicarb of soda should make a big difference.
Some Roses Are More Prone Than Others
It is worth saying this clearly: some rose varieties are just more prone to blackspot than others.
That does not mean you have done anything wrong. You can prune well, clean up fallen leaves, water carefully, and still find that certain roses get blackspot every season. Some older hybrid teas and very popular fragrant roses are beautiful, but they can need more disease care than tougher modern shrub roses.
For example, Mister Lincoln is a much-loved deep red rose with a wonderful fragrance, but it is also known to be susceptible to blackspot. Peace is another famous old favorite that many gardeners still grow, but in some gardens it can also need regular attention to stay clean.
I still think some roses are worth growing even if they are not perfectly disease-free. You just need to know what you are dealing with and decide whether the flowers are worth the extra care.
Final Thoughts
Blackspot is frustrating, but it is also very common. The aim is not always to have a perfectly spotless rose garden. Sometimes the aim is simply to keep the disease under control so the plant can keep growing, flowering, and looking reasonably healthy.
If one rose gets blackspot every single year no matter what you do, it may simply be a variety that is prone to it. In that case, you can either accept the extra care, move it to a better spot with more air movement, or eventually replace it with a more disease-resistant rose.
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