Summer in Perth brings out the very best in our roses: brilliant blooms, beautiful foliage, and the sheer joy of a healthy garden. But high temperatures and warm nights also mean it’s prime time for certain pests and diseases to make an appearance. I believe that healthy roses start with knowing what to look for and being prepared. Here’s Part 1 of a guide to the most common threats facing Perth roses in summer—plus practical tips to keep your bushes thriving through the heat.
Fungal Foes: What to Watch For
Among the most prolific threats in Perth’s warm climate are fungal diseases. Powdery mildew is notorious in our region, appearing as a white, powdery coating on leaves, stems, and buds. It loves cool nights following hot days, which are all too common in a Perth summer. Keeping plants well-spaced, ensuring good air circulation, and preventing overhead watering can help reduce its spread. If you spot powdery mildew, promptly remove affected leaves and consider organic fungicide sprays.
Rust, recognizable by its orange or rust-coloured spots on the undersides of leaves, can defoliate roses if left unchecked. It thrives in humid conditions and can quickly spread. Regular checking and early removal of infected foliage, along with clean-up of leaf litter, are essential.
Black spot—a disease marked by black circular spots with yellow halos—weakens roses by causing premature leaf drop. It often appears after periods of high humidity or overnight dew. Removing and destroying affected leaves, both on the plant and fallen on the ground, will help, as will regular fungicide applications if needed.
If you need help to care for your roses, please call me.
John Kelly