Cause Melampsora lini, a fungus that survives year to year in flax stubble and moves by spores from field to field. Spores also can be carried on small pieces of plant debris mixed with seed. The fungus has many different races, each of which infects a different set of Linum spp. Weakens plants and reduces quality and yield of linseed.
Symptoms Light-yellow to orange-yellow spots (pycnia and aecia) appear on leaves and stems in spring. Later, reddish yellow uredinia form on leaves and stems followed by the black telia late in the season.
Cultural control
- Use resistant cultivars.
- Avoid excessive nitrogen fertilization.
- Plow in infected stems and stubble after harvest.
- Rotate crops and remove wild or volunteer plants.
- Use clean seed.
Chemical Control Materials below are registered for control of other diseases in flax seed crops only and could help with rust control but applications must adhere to limits on timing and number of applications allowed.
- Strobilurin fungicides (Group 11) are labeled for use. Do not make more than one (1) application of a Group 11 fungicide before alternating to a labeled fungicide with a different mode of action.
- Headline SC or Headline at 6 to 12 fl oz/A at mid-flowering and again 7- to 10-days later for up to two (2) applications. Preharvest interval is 21 days. 12-hr reentry.
- Quadris Flowable at 6 to 15.5 fl oz/A as a 7-oz application at early bud followed by a 14-oz at 45 days before harvest. Preharvest interval is 30 days. 4-hr reentry.
- Sulfur formulations are labeled for use.
Reference Laundon, G.F. and Waterston, J.M. 1965. Melampsora lini. CMI Descriptions of Pathogenic Fungi and Bacteria, No. 51. Surrey, England: Commonwealth Mycological Institute.