Needle Rusts

Gymnosporangium spp.

42 host plants · Fungal

Last updated

Data Maturity Baseline

This profile contains verified disease data from extension databases. Regional field notes and expert review are in progress.

Pine needles develop rust pustules and may drop prematurely from Gymnosporangium species, which alternate between conifers and deciduous hosts. Separate pines from nearby junipers and hawthorns by 0.5-2 miles if possible. Prune galls from junipers in spring before spore release; remove infected deciduous foliage promptly.

Rust fungi often need two different host plants to complete their life cycle, so identifying and managing the alternate host can break the cycle. Remove heavily infected leaves and dispose of them away from the garden. Improve air circulation to speed leaf drying after rain. Fungicide applications are most effective as preventive treatments before symptoms appear; once pustules are visible, the current infection cycle is already underway.

Quick Reference

Agent Type
fungal
Causal Agent
Gymnosporangium spp.
Host Plants
42
Spread
Basidiospores from juniper telia to alternate host needles/leaves; aeciospore...
Favorable Conditions
Wet spring weather at temperatures 50-65°F triggers telia swelling and basidi...

Management

Vulnerability Window

Juniperus (telial host): telia present April-May during spring wet season. Pine hosts: susceptible during spring needle emergence (April-June). (Source: PNW Plant Disease Management Handbook)

What Triggers Infection

Wet spring weather at temperatures 50-65°F triggers telia swelling and basidiospore release from Juniperus hosts. Infection of pine needles occurs during spring growth in cool, moist conditions. (Source: Gymnosporangium spp. lifecycle; PNW climate phenology)

Cultural Controls

  • Check the vicinity for infected juniper; if they have no value, remove them. If you are growing both hosts as crops, separate them as widely as possible. Separating hosts by 0.5 to 2 miles has been recommended.
  • Prune out any visible galls or swellings on juniper before spring and remove visible infections on hawthorn or other deciduous hosts before spring spore release.
  • Collect and burn infected leaves. Space plants for good air circulation and rapid drying.

Host Plants (42)

Pinus albicaulis Whitebark Pine, Scrub Pine, White Pine Pinus aristata Bristlecone Pine, Rocky Mountain Bristlecone Interior Bristlecone Pinus attenuata Knobcone Pine Pinus banksiana Jack Pine, Scrub Pine, Banksian Pine, Hudson Bay Pine Pinus bungeana Lacebark Pine, Whitebark Pine, Baipi Song Pinus canariensis Canary Island Pine Pinus cembra Swiss Stone Pine Pinus contorta Lodgepole Pine Pinus contorta var. contorta Shore Pine Pinus contorta var. latifolia Rocky Mountain Lodgepole Pine Pinus coulteri Coulter Pine, Bigcone Pine Pinus densiflora Japanese Red Pine Pinus edulis Pinyon Pine, Piñón Pine, Two-needle Pinyon Colorado Pinyon Pinus elliottii Slash Pine, Swamp Pine Pinus flexilis Limber Pine, Rocky Mountain White Pine Pinus halepensis Aleppo Pine, Jerusalem Pine Pinus heldreichii Bosnian Pine, Snakeskin Pine Pinus jeffreyi Jeffrey Pine, Western Yellow Pine, Bull Pine Pinus kwangtungensis Kwangtung Pine, Guangdong Pine Pinus lambertiana Sugar Pine Pinus leucodermis Bosnian Pine Pinus monophylla Singleleaf Pinon Pine, One-leaved Pine Pinus monticola Western White Pine Pinus mugo Mugo Pine Pinus mugo var. pumilio Mugo pine, Dwarf Mugo pine Pinus nigra Austrian Pine Pinus parviflora Japanese White Pine Pinus parvifola Pinus parvifola Pinus pinaster Maritime Pine, Cluster Pine, Turpentine Pine Pinus pinea Italian Stone Pine, Umbrella Pine Pinus ponderosa Ponderosa Pine, Western Yellow Pine Pinus pumila Japanese Stone Pine, Dwarf Siberian Pine Pinus radiata Monterey Pine Pinus resinosa Red Pine Pinus sabiniana Gray Pine, Foothill Pine Pinus strobiformis Southwestern White Pine, Mexican White Pine, Chihuahua White Pine Pinus strobus Eastern White Pine Pinus sylvestris Scots Pine, Scotch Pine Pinus thunbergii Japanese Black Pine Pinus virginiana Virginia Pine, Scrub Pine, Jersey Pine Pinus wallichiana Himalayan Pine, Bhutan Pine Pinus yunnanensis Yunnan Pine