Hawthorn: Rust

• Categories: Hawthorn Hawthorn Diseases Ornamental trees Ornamentals
• Last review date: 2026-05-15 09:39

Biology

Rust is a fungal disease typically infecting leaves of hawthorn (occasionally also apple and crabapple). It may also be found on green stems and fruit.

Initial symptoms are the presence of yellow to orange spots or pustules on the leaves. Severe infections may cause leaves to turn yellow and drop.

Rust on stems and fruit causes these parts to be deformed. Mature sporulating rust infections are characterized by hairlike projections which bear the fungal spores.

The alternate hosts for hawthorn rust are junipers, which develop swollen galls along the twigs. The juniper galls release orange spores in the spring.

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!

• Plant resistant species or varieties such as Crataegu crus-galli, C. flava, C. intricata, C. laevigata ‘Autumn Glory’, C. phaenopyrum, C. pruinosa, or C. viridis ‘Winter King’.
• Remove alternate host
  (junipers) from the area when practical.
• Prune and destroy diseased leaves and branches on hawthorns in summer before sporulation. Prune out galls on junipers before sporulation in the spring.
• Avoid overhead watering.
• Space plantings and prune to improve air circulation and reduce humidity.

Chemical Management

• Protect new growth on hawthorn when fungal infections on juniper are active (between mid-March and mid-May).
• 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 Fung-onil Multi-Purpose Fungicide Concentrate
  Active ingredient: chlorothalonil
  EPA registration number: 60063-9-4
• 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
• Spectracide IMMUNOX Multi-Purpose Fungicide Spray Concentrate
  Active ingredient: myclobutanil
  EPA registration number: 9688-123-8845
• This list may not include all products registered for this use.