Many fungal species
Hosts, Symptoms & Signs
- many hosts; commonly seen on hollyhock, roses, hawthorn, flax, cottonwoods and fir (at higher elevations)
- rusts are very host specific and rarely kill the host plant
- orange blisters occur on plant tissue at infection points
- ruptured blisters release orange-colored spores that can cause new infections
- deformed growth in conifers
- early defoliation can occur in deciduous trees
- overwinter on living host material
- in spring, spores are wind dispersed over great distances
- the disease cycle is typically completed on one or two hosts
- rust is an obligate parasite and requires a living host
- Manage trees to improve or maintain overall health.
- Use resistant plant varieties when available.
- Remove alternate hosts to break the disease cycle.
- Remove infected plant material to prevent spread to uninfected plants and to prevent overwintering.
- Plant farther apart to allow for air movement and a reduction in humidity.
- Apply a preventative fungicide (chlorothalonil; myclobutanil; tebuconazole) to protect healthy leaves.
- Leaves with fruiting structures (orange blisters) cannot be saved.