Poplar: Leaf rust

• Categories: Ornamental trees Ornamentals Poplar Poplar Diseases
• Last review date: 2026-08-28 02:15

Biology

Rusts of poplar are fungal diseases which usually require alternate hosts to complete their life cycle. They overwinter on the poplar leaves, then infect the alternate host in the spring (alternate hosts include pines, larch, and Douglas fir, depending on the rust species).

Infection of new poplar leaves occurs around midsummer. Bright yellow or orange velvety rust pustules develop on either or both leaf surfaces (mainly on the underside).

Severe infections cause leaves to develop large yellow areas. In fall, the rust pustules may also show dark brown areas, which are associated with dead gray to brown spots on the other side of the leaf.

Heavy infections can result in considerable leaf loss. Rust fungi are favored by mild, wet weather.

Management Options

See "Using Integrated Pest Management (IPM) in the Landscape" for successful problem management techniques.

Non-chemical Management

Select non-chemical management options as your first choice!

• Do not plant alternate hosts in close proximity to susceptible poplars.
• Provide proper culture. Healthy plants are more tolerant of disease.
• Space plantings and prune to improve air circulation.
• Avoid overhead watering.
• Rake and destroy leaves from infected trees.
• Prune and destroy severely infected shoots of either host when noticed.

Chemical Management

• Effective if applied shortly after rust appears.
• Homeowners should not make foliar applications to trees over 10 ft tall.
• Consult a commercial pesticide applicator for treatment of trees and shrubs over 10 ft. tall.

Approved Pesticides

If you choose to use a pesticide, some examples of products that are legal in Washington are listed below. Some products are labeled for just INDOOR or just OUTDOOR use, or may allow both uses. Be sure to choose a product appropriate for your situation. Always read and follow all label directions.

• Bonide Infuse Systemic Disease Control
  Active ingredient: propiconazole
  EPA registration number: 100-773-4
• GardenTech Daconil Fungicide Concentrate
  Active ingredient: chlorothalonil
  EPA registration number: 67572-82-71004
• Ortho Max Garden Disease Control Concentrate
  Active ingredient: chlorothalonil
  EPA registration number: 239-2522
• This list may not include all products registered for this use.