WSU Extension


Bacterial blight 
Leaf and shoot blight 
Leaf blister 
Leaf rust 
Marssonina leaf spot 
Oystershell scale 
Poplar petiole gall aphids 
Poplar-and-willow borer 
Satin moth 
Tent caterpillars 

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Caption: Poplar rust
Photo by: R.S. Byther
Poplar : Leaf rust
(revision date: 4/11/2018)

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

Non-Chemical Management
  • 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.
Select non-chemical management options as your first choice!

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.

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.
  • Bonide Fung-onil Multi-Purpose Fungicide Conc
    Active ingredient: chlorothalonil  |  EPA reg no: 60063-9-4
  • Bonide Infuse Systemic Disease Control
    Active ingredient: propiconazole  |  EPA reg no: 100-773-4
  • GardenTech Daconil Fungicide Conc
    Active ingredient: chlorothalonil  |  EPA reg no: 67572-82-71004
  • Ortho Max Garden Disease Control Conc
    Active ingredient: chlorothalonil  |  EPA reg no: 239-2522
  • This list may not include all products registered for this use.

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Caption: Poplar rust
Photo by: R.S. Byther
Caption: Poplar rust
Photo by: R.S. Byther