Rust
Orange, brown or black powdery pustules, usually on the leaf undersides, with small yellow spots above. Badly affected leaves drop; common on roses, hollyhocks, leeks, beans, pears (orange spots) and willows.
Rust fungi spread in damp weather; some, such as pear rust, alternate between two hosts, here pear and ornamental juniper.
What can you do?
- Pick off affected leaves and clear up fallen ones; put them in the green waste bin or general waste, not on your compost heap.
- Give plants more space and water at the base to keep the leaves dry.
- For pear rust: remove ornamental junipers (Juniperus sabina and relatives) with rust galls near your pear, or prune out the galls.
Prevention
Choose resistant varieties, go easy on nitrogen and pick an airy spot. Rotate leeks and beans every year.
When to watch out: May–September