Cause Tranzschelia discolor and T. pruni-spinosae, fungi widespread in prunes and plums. Rust has been considered a curiosity rather than a problem in Oregon; however, rust may be severe some years in prune plantings in western Oregon. The alternate host is Anemone sp.
Symptoms Yellow spots on leaves cause pustules (uredinia and telia) of brown spores on lower leaf surfaces. Infected leaves develop a yellowish cast; leaf shedding may be severe. The condition becomes increasingly prevalent toward the end of summer.
Cultural control Specific cultural control tactics have not been investigated.
Chemical control Control may be obtained when fungicides are used to control brown rot. Tank-mix or alternate chemicals to prevent fungi from developing resistance. Limit the use of any one group during crop production.
- Abound at 12 to 15.5 fl oz/A. Do not apply with silicone-based surfactants. May be applied the day of harvest. Sprayers should not be used on apples. Group 11 fungicide. 4-hr reentry.
- Eagle 20 EW at 2 to 3 fl oz/100 gal water for home orchards or landscape use. Can be applied up to the day of harvest. Group 3 fungicide. 24-hr reentry.
- Flint Extra at 2.5 to 3.8 oz/A. Do not apply within 1 day of harvest. 'Concord' grapes may be injured if accidentally sprayed. Group 11 fungicide. 12-hr reentry.
- Inspire Super at 16 to 20 fl oz/A. Do not apply within 2 days of harvest. Group 3 + 9 fungicide. 12-hr reentry.
- Luna Experience at 8 to 10 fl oz/A. May be used day of harvest. Group 3 + 7 fungicide. 12-hr reentry.
- Luna Sensation at 5 to 7.6 fl oz/A. Do not use within 1 day of harvest. Group 7 + 11 fungicide. 12-hr reentry.
- Miravis at 5.1 fl oz/A. Can be used up to the day of harvest. Group 7 fungicide. 12-hr reentry.
- Miravis Duo at 13.6 fl oz/A. Can be used up to the day of harvest. Group 3 + 7 fungicide. 12-hr reentry.
- Propiconazole-based fungicides are registered. Do not use on Stanley-type plums earlier than 21 days before harvest. Group 3 fungicides.
- PropiMax EC at 4 fl oz/A. Do not use within 10 days of harvest. 12-hr reentry.
- Tilt at 4 oz/A. May be used up to and including day of harvest. 24-hr reentry.
- Quadris at 12 to 15.5 fl oz/A. May be applied the day of harvest. Sprayers used for Abound should not be used on apples. Group 11 fungicide. 4-hr reentry.
- Quadris Top at 12 to 14 fl oz/A. May be applied on the day of harvest. Group 3 + 11 fungicide. 12-hr reentry.
- Quash at 3.5 oz/A. Do not use within 14 days of harvest. Do not use on Stanley-type plums. Group 3 fungicide. 12-hr reentry.
- QuiltXcel at 14 fl oz/A. May be applied the day of harvest. Do not use on Stanley-type plums earlier than 21 days before harvest. Sprayers should not be used on apples. Group 3 + 11 fungicide. 12-hr reentry.
- Rhyme at 7 fl oz/A. Do not use within 7 days of harvest. Group 3 fungicide. 12-hr reentry.
- Spectracide Immunox Multi-Purpose Fungicide Spray Concentrate for Gardens at 0.5 fl oz/gal water. May be applied up to the day of harvest. Do not use more than seven (7) times per season. Group 3 fungicide. H
- Tebucon 45 DF at 5 to 8 oz/A for "fresh" prunes only. Can be applied up to and including day of harvest. Group 3 fungicides. 5-day reentry.
- Topguard EQ at 6 to 8 fl oz/A. Do not use with silicone surfactants or within 7 days of harvest. Sprayers should not be used on apples. Group 3 + 11 fungicide. 12-hr reentry.
Reference Ogawa, J.M. and English, H. 1991. Diseases of Temperate Zone Tree Fruit and Nut Crops. University of California. p461.