An organic treatment for Black Spot on Roses

For any rose growers that are searching for an organic treatment for black spot on roses.

What is Rose Black Spot?

Black spot on roses is caused by a fungus, Diplocarpon rosae, and is one of the most serious diseases that affect roses. Dark brown to black spots appear on the leaves, gradually increasing in size, and ultimately turning the leaf yellow before it falls from the stem. Left untreated, black spot will spread to other leaves on the plant, and soon to other roses nearby.

According to the RHS, “badly affected plants can shed almost all their leaves and their vigour is greatly reduced. The symptoms are so severe that, anecdotally, the disease has been blamed for a decline in the popularity of roses in gardens in recent decades”

Royal Horticulture Society

How do you treat black spot on roses?

If, like me, you are averse to using chemicals in your garden, an organic treatment for black spot on roses is desirable. And that organic treatment comes in the form of milk. But more on that later.

The first step to be taken when treating rose black spot is to remove all of the affected leaves. This may result in the rose being left as a bare stalk, but don’t worry, this does not hinder the flowering of the plant and new leaves will grow back. As well as removing the diseased leaves, you should collect any of the fallen leaves from around the base of the plant. The fungus will linger here and continue to infect year after year. The removed and collected leaves should be destroyed. Do not put them in your compost bin, as again, the fungus will linger. The next step is to add a good layer of mulch around the base of the plant, such as woodchip.

Now, the organic treatment for black spot on roses. Mix up a solution of 1 part milk (full fat milk) to 2 parts water in a spray bottle. Spray the remaining leaves of the plant with this solution, and repeat every week. One word of warning would be to do this in the evening, as the smell of milk in the garden on a hot day is not great!

Can roses recover from black spot?

My own roses were suffering badly with blackspot – so much so, and as the RHS have already pointed out, I was going to give up on them. Deciding to take drastic action, I began by stripping all of the infected leaves. I carried out the organic treatment regime of spraying the 2 to 1 water/milk solution every week for a month, and my roses did recover, as you can see in the images. Keeping the plants as healthy as can be gives them a better chance. Giving them 5 litres of water per week (as per the David Austin’s basics of growing roses) and watering at the base. A good tip I got on Instagram was to remove the bottom few leaves to stop them getting splashed.