It’s not hard to miss Black Spot on roses because it is an obvious discolouration on the leaves and sometimes on the stems and branches.
There is no rose-growing area in Australia that is free from Black Spot but you’re roses are move likely to be infected if you live in an area with high summer rainfall and high humidity.
So, wherever you live Black Spot is going to be a problem that you have to deal with and the battle will be ongoing. Now that doesn’t sound terribly encouraging but, with the right care, your roses can have a better chance of fighting off black spot infection.
Causes and spread
Black Spot is caused by two fungal pathogens that only attack roses and the disease is spread by water. That may sound rather strange and it is when you consider that the spores of these pathogens spread when a water droplet splashes on an infected area. Water splashes on the black spot and the spores are then carried the spray from each splash.
Black Spot infections can spread faster on leaves and plants that are located in areas of poor light and poor air flow and the way a plant is watered can also help spread the spores.
When it’s time to prune there are several things you need to do to prevent the spread of this disease.
The first thing to do is to make sure that infected leaves and branches aren’t left on the ground. Pick everything up and put it in the garbage bin. Do not add them to your compost heap.
The second thing to do is to keep your secaturs clean. To do this you need a container filled with bleach that you can dip your secatur blades into between every cut.
If the Black Spot has reached the stems and branches prune right back to good wood and then spray with a garden fungicide. Yates have several products that are suitable or your local nursery can help you with other brands.
You should also remove any infected leaves or stems and spray during the growing and flowering season.
Healthy plants can do a lot to fight off Black Spot infections so be sure to feed your plant through the growing season.
The way you water your roses can go a long way to preventing an outbreak of Black Spot. If you can water the base of the plant without getting the water on the leaves then your ahead of all the others who choose to water from the top down.
Planting your roses in the right place is also a good way to keep Black Spot away. Plant them in a sunny area and don’t clump them together. Allow plenty of space between each plant so that air can move through the garden and help keep the leaves dry.
And be on the lookout for the first signs of an infection and remove the infected leaves before the spores have a chance to spread.