Wheat (Triticum aestivum) - Stem Rust (Black Rust)
Barberry (Berberis spp.) - Rusts
Cause Cumminsiella mirabilissima and Puccinia graminis, fungi. These diseases can be spread through infected nursery stock. Cumminsiella mirabilissima has all spore stages on the same host, while P. graminis has grass alternate hosts such as wheat. The movement of rust resistant cultivars is not regulated.
Telia of C. mirabilissima occur on leaves in the fall and teliospores are abundant in March and April. Newly emerging leaves are infected by basidiospores produced from teliospores. Pycnia then develop on the upper leaf surface from late April to mid-June. Aecia then develop on the undersides of leaves along veins, petioles and leaf margins or even on fruit, especially by the end of May. By late June uredinia can be found on the undersides of leaves. By fall telia are produced in the center of the uredinia.
In the laboratory, Oregon grape can be an alternate host for Puccinia striformis f. sp. tritici, wheat stripe rust. It is not known if this can also occur in nature.
Symptoms Reddish spots on older leaves which develop dark centers (telia). Severe infections cause leaves to be puckered and distorted and may lead to premature defoliation. The aecidial stage, on younger leaves, is rare. On older leaves, once aeciospores are released, infected areas abscise and develop a shot-hole like symptom. The golden yellow margin of the peridia distinguishes C. mirabilissima from Puccinia graminis, which has a whitish or yellow margin.
- Avoid overhead irrigation.
- Remove and destroy infected leaves.
- Grow rust resistant cultivars or species.
Chemical control Protect newly emerging leaves.
- Bonide Fung-onil Multi-purpose Fungicide at 2.25 teaspoons/gal water. H
- Daconil Weather Stik at 1.38 pints/100 gal water. Group M5 fungicide. 12-hr reentry.
- Ortho MAX Garden Disease Control at 2 teaspoons/gal water. H
- Spectro 90 WDG at 1 to 2 lb/100 gal water. Group 1 + M5 fungicide. 12-hr reentry.
- Terraguard SC at 2 to 8 fl oz/100 gal water to control Puccinia spp. Group 3 fungicide. 12-hr reentry.
References Punja, Z.K. 1979. Occurrence of Cumminsiella rust of Mahonia in British Columbia. Canadian Journal of Plant Pathology 1:107-110.
Wang, M.N., and Chen, X.M. 2013. First report of Oregon Grape (Mahonia aquifolium) as an alternate host for the wheat stripe rust pathogen (Puccinia striiformis f. sp. tritici) under artificial inoculation. Plant Disease Note 97:839.