Pear Rust
Risk near you, next 48h
See whether your local forecast favours this disease right now.
When it strikes
Treat, then re-check in 5–7 days
Pick off the worst material, apply the organic option below, and look again after five to seven days. If the spread continued, escalate rather than repeating the same treatment.
Rain and irrigation splash
Water splashing off soil and infected leaves carries it upward and along the row. Watering at the base and mulching the soil surface break the route.
It carries over to next season in soil, debris or seed — which is why rotation matters here, not just treatment.
Hot compost only
A heap that reaches and holds 55–65°C throughout will destroy it. A cool corner heap will not, and will return the problem to the beds with the finished compost.
When and where to look
Scout the planting while temperatures hold between 12°C and 24°C, with humidity above 85%, after rain or heavy dew, while the leaves are still wet. Risk builds after roughly 6 unbroken hours of those conditions, so the morning after such a night is the moment to look.
Rule these out first
Same category, and at least one host crop in common — so they are genuinely confusable in the same part of the garden.
The signs that lead here
Full problem lists for these crops
About
Pear rust (Gymnosporangium sabinae) needs two hosts to complete its life cycle: a juniper, where it overwinters, and a pear, where it does the visible damage. It has spread rapidly across Europe wherever ornamental junipers have been planted near fruit trees.
Symptoms
Bright orange spots with a red rim appear on the upper leaf surface from late spring. By late summer each spot develops a cluster of brown, horn-like outgrowths on the underside. Heavily spotted leaves drop early and the tree loses vigour.
Organic Treatment
There is no organic spray that cures it — the cure is the juniper. Remove every Juniperus sabina, chinensis and virginiana within a few hundred metres, or at minimum cut out the swollen, gelatinous galls on their stems in early spring before the spores release.
Chemical Treatment
Triazole fungicides (difenoconazole, tebuconazole) applied from bud burst at 10–14 day intervals reduce infection, but they only protect new growth and cannot stop reinfection while a juniper host stands nearby.
Prevention
Never plant junipers near pears. Rake and remove fallen leaves in autumn, keep the tree vigorous with balanced feeding, and choose resistant pear varieties where the disease is established locally.
Crops at risk
Related problems
Pear Rust risk by location
Each location has a month-by-month profile computed from the weather archive: how many hours a year actually meet this disease’s thresholds.