As autumn approaches, it brings with it more cold, wet weather and the ‘most serious disease of roses’ according to the RHS.
Rose black spot, also known as Diplocarpon rosae, is a fungal disease that infects the perennial species’ leaves, causing black or purple spots to appear on the surface and leaves the flower vulnerable to other disease ahead of the winter months.
The disease thrives in cold and wet weather, “the rain allows the spores to germinate and the splash spreads the spores, and it can spread quite quickly,” says Guy Barter, chief RHS horticultural advisor.
If left untreated it can cause rose plant leaves to shed, reducing its chances of reflowering the next year.
With symptoms ‘so severe that, anecdotally, the disease has been blamed for the decline in popularity of roses in UK gardens in recent decades,’ says the RHS.
“At the end of the season you can reduce the infection pressure for the following year by pruning out the worst of the damaged foliage, picking up infected leaves.”
Black spot is among the most common fungal diseases, that “few roses in Britain are completely unaffected.”