BLACK spot is the rose growers’ eternal nemesis. A fungal disease, black spot displays as exactly what the name says … black spots on the leaves of roses.
If it’s a problem on your roses now, it’s almost too late to worry about trying to fix it.
It thrives in wet and humid conditions and our summer climate.
The disease starts as a small black spot, which grows to about 1cm across. The leaves turn yellow and fall off, and if the infection is bad the rose can die.
The time to start managing your roses to prevent black spot becoming a problem is as soon as the new growth starts to appear after winter pruning.
Clean up any fallen rose leaves under the plants as these could harbour black spot fungal spores.
Spray your roses all over with a triforine-based fungicide spray (like Trifend or Rose Shield) and the ground around them too. This will neutralise any fungus spores on the plant or on the soil/mulch surface.
After that, you need to undertake an alternating fortnightly treatment of two types of sprays.
Firstly, spray with a copper-based fungicide as per the label instructions – Yates have a few different products.
A fortnight later, in a bucket of water mix 100g of bicarbonate of soda, 5ml of seaweed extract and a couple of drops of a dish washing liquid (or a wetting agent such as Searles Spedmax). Spray this over the whole plant.
Alternate and repeat these sprays right through the Autumn, Spring and Summer months as a fungal prevention regime.
At the same time, keep your plants strong, healthy and able to fight diseases by regularly (every six weeks) applying a rose fertiliser, like Dynamic Lifter for roses. You can stop the fertilising in Winter.
Every three months apply a handful of sulfate of potash around each plant as well. The potassium in sulfate of potash stimulates the growth of strong plant cells, helping the plant increase its disease resistance.
Mulch around the roses with a layer of cow manure topped with sugarcane mulch.
Good plant hygiene is also important, so clean up any fallen leaves and bin them – not in the compost.
Following this simple approach will give your roses the best chance at living a healthy, disease-free life, and they’ll reward you with spectacular displays of glorious roses for years to come.
