Skip to content Skip to navigation
UMass Collegiate M The University of Massachusetts Amherst
  • Visit
  • Apply
  • Give
  • Search UMass.edu
Center for Agriculture, Food, and the Environment
UMass Extension Landscape, Nursery and Urban Forestry Program
  • LNUF Home
  • About
    • Program Overview
    • Faculty & Staff
    • Contact Information
    • Disclaimer
  • Newsletters & Updates
    • Landscape Message
    • Hort Notes
    • Garden Clippings
  • Publications & Resources
    • Fact Sheets
    • Weed Herbarium
    • Professional Disease Guide
    • Professional Insect & Mite Guide
    • Nursery Best Management Practices (BMP) Manual
    • Garden Calendar
    • Useful Links
    • Association Certification
    • Pesticide License Information
    • Pesticide Resources
    • Nutrient Management
  • Services
  • Education & Events
    • Events
    • News
    • Green School
    • Invasive Insect Certification
    • Invasive Plant Certification
    • Turf Winter School
    • InsectXaminer
    • Invasive Insect Webinars
    • TickTalk with TickReport Webinars
    • Pollinator Steward Certification Program
  • Make a Gift

Spruce Needle Rust

Image
Swollen and rupturing lesions on one-year-old blue spruce (Picea pungens) needles infected by Chrysomyxa weirii
Image
Spore dispersal from one-year-old needles corresponds with budbreak on blue spruce (Picea pungens) from early to late May
Image
Erupting pustule of rust-colored spores from an infected Serbian spruce (Picea omorika)

Spruce needle rust, also known as Weir's cushion rust, is caused by the fungus Chrysomyxa weirii. 

Hosts

Most spruce (Picea) species are susceptible to the disease but Colorado blue spruce (P. pungens) is particularly susceptible. Other common hosts include white spruce (P. glauca), black spruce (P. mariana), red spruce (P. rubens) and Sitka spruce (P. sitchensis).

Symptoms & Disease Cycle

In late winter to early spring, orange to yellow spots or bands appear on one-year-old needles. In late winter, the symptoms may be hard to detect, but when spring advances and bud break approaches in early to mid-May, the bands swell to produce waxy, yellow-orange pustules containing masses of rust-colored spores. At bud break, the pustules erupt and the spores are dispersed by wind and rain to newly emerging needles on nearby shoots. Wet weather will prolong the spore production period. Newly infected needles do not show symptoms until the following winter or spring. After the pathogen sporulates on one-year-old, they may become rusty brown and drop during the summer. As with most needle diseases, spruce needle rust tends to affect the lower branches more severely but, because C. weirii spores are wind dispersed, the upper foliage may also be infected over time. Severely infected trees can have a orange-colored appearance from the lesions and repeated defoliation can retard growth and reduced aesthetic appearance. However, in many cases the disease is not particularly desctructive to otherwise healthy trees but does reduce their aesthetic value. Spruce needle rust is differs from other common landscape rust diseases (e.g. cedar-apple rust) in that the pathogen is autoecious; it occurs only on spruce and has no known alternate host.

Management

When the disease is severe, infected shoots can be pruned to slow or potentially stop the spread of the disease to newly developoing needles. Pruning of diseased shoots should take place in late spring when the needle lesions are visible but have not yet ruptured to release spores. Removal of severely infected trees will reduce spread of wind-blown spores to nearby healthy trees but this action is rarely required in most landscape settings. Disease severity tends to be higher when spruce are growing in tight hedgerows or in deep shade. Fungicides may be practical to protect new growth and stop spread of the disease on small, high-value specimen trees. Copper hydroxide or mancozeb can be effective and is labeled for use on spruce in the landscape. The first application should be made just before bud break and subsequent applications made on labeled intervals until needles mature. Trees infected with spruce needle rust, especially blue spruce, are often harboring additional needle and stem diseases (e.g. Rhizosphaera and Stigmina needle cast) in addition to insect and mite problems.

Author: Nicholas Brazee
Last Updated: March 8, 2018

Connect with UMass Extension Landscape, Nursery and Urban Forestry Program:

Facebook   Twitter

Subscribe to GreenInfo Mailing List »

Home Lawn & Garden Information »

Center for Agriculture, Food, and the Environment

 

Stockbridge Hall,
80 Campus Center Way
University of Massachusetts Amherst
Amherst, MA 01003-9246
Phone: (413) 545-4800
Fax: (413) 545-6555
ag [at] cns [dot] umass [dot] edu (ag[at]cns[dot]umass[dot]edu)

 

Civil Rights and Non-Discrimination Information

College of Natural Sciences

Login for faculty and staff

CAFE Units

Mass. Agricultural Experiment Station

UMass Extension

UMass Research and Education Center Farms

UMass Cranberry Station

Water Resources Research Center

Interest Areas

Agriculture

Commercial Horticulture

Energy

Environmental Conservation

Food Science

Nutrition

Water

Youth Development & 4-H

Services

Pesticide Education

Plant Diagnostics Laboratory

Soil and Plant Nutrient Testing Laboratory

Hot Water Seed Treatment

Water Testing / Environmental Analysis Laboratory

Projects

Conservation Assessment Prioritization System (CAPS)

Extension Risk Management/Crop Insurance Education

Mass. Envirothon

Mass. Herp Atlas

Mass. Keystone

MassWoods

North American Aquatic Connectivity Collaborative

RiverSmart

UMass Design Center in Springfield

Resources

Extension Sales Portal

Agriculture & Commercial Horticulture Resources

Community & Economic Vitality

Disaster Preparedness

Food Safety

Home Lawn & Garden

Integrated Pest Management (IPM)

Land Conservation Tools

Pollinators

Tick testing

Resources for Faculty and Staff

Extension Programs

4-H Youth Development

Agriculture

Crops, Dairy, Livestock and Equine

Fruit

Greenhouse Crops and Floriculture

Landscape, Nursery and Urban Forestry

Pesticide Education

Turf

Vegetable

Clean Energy

Climate Change

Food Science

Nutrition Education

Value-Added Food

Seal of The University of Massachusetts Amherst - 1863
©2025 University of Massachusetts Amherst · Site Policies · Accessibility