Stem rust [Puccinia graminis f. sp. secalis ]
Stem rust - image 1
All grain varieties, in Germany it is only a problem in rye.
Pattern of damage
From mid-June, rust-red to chocolate-brown longitudinal pustules can be found on leaf sheaths and stems (Picture 1). These are the summer fruiting bodies. They have an outline with a clearly slit epidermis and are arranged in stripes. The teleutosporocarps are also arranged in stripes and extended lengthwise, breaking out of the epidermis. Stem rust can be confused with brown rust. However, stem rust is easily distinguished due to the bursting epidermis around the fruiting body, and the striated arrangement.
Good tilling of crop residue. Cultivation of early-maturing varieties. Correct fertilization. Fungicide measures: No dedicated fungicide measures but fungicide measures against brown rust provide sufficient control of early emerging stem rust as well.
Spread/ transmission: The telial spores germinate in spring on crop residues at a humidity of 95%. These form another type of spore: basidiospores. They germinate on the intermediate host barberry in favorable weather, and grow into an inter-cellular mycelium. Small orange-red sporocarps develop below the epidermis at the upper side of the leaf. On the underside of the leaf, cup-like fruiting bodies (aecia) develop via a sexual stage. The aecia, which are spread by the wind, infect the main host. Favorable infection conditions include the existence of dropping water and temperatures of 5-22 °C. Multiple generations of summer fruiting bodies (uredospores) develop on stems and the leaf sheath, forming dense colonies on the cereal crop. Winter fruiting bodies (teleutospores) develop on ripening grain.