Winter Wheat Production Manual

Written by D. B. Fowler
Crop Development Centre
University of Saskatchewan

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Strawbreaker Foot Rot

Strawbreaker or eyespot is also known as foot rot because it attacks the base of the plant. Growth and development of this fungus is favored by moist conditions and temperatures near 10oC. Thick crop stands that maintain a high relative humidity within the canopy provide the most favorable environment for the development of this disease.

[ Images | Causes and Symptons | Losses | Control ]

a) Causes and Symptoms:

Spores of the strawbreaker fungus (Pseudocercosporella herpotrichoides) are produced on moist infected crop residues in the fall and spring. Newly established crops are mainly infected by spores that are splashed up onto the plants by raindrops. Dry weather discourages spore production and the spread of the strawbreaker fungus.

Eye-shaped lesions that develop at the base of the stem are the most distinctive feature of strawbreaker. The lesions first appear as small, water soaked spots on the leaf sheaths of young plants. These spots become more distinctive after stem elongation (Zadoks growth stage 30) when they extend through the leaf sheath and penetrate the stem. The color of the lesions progresses from a light to a dark brown as the disease develops. The lesions have an elliptical shape and are positioned lengthwise to the stem, hence the name eyespot. They weaken the stem making the plants more prone to lodging. The name strawbreaker comes from the tangled mass of lodged plants that break over near the soil surface when infections by this disease are severe.
[ Images | Causes and Symptons | Losses | Control ]

b) Losses:

Strawbreaker is an important disease of wheat in cool, moist climates. It has caused severe damage in the North American Pacific Northwest and has been an occasional problem in the Ontario, Michigan, and New York areas. Damage from this disease has also been reported in Kansas.

Only one outbreak of strawbreaker foot rot has been reported in winter wheat in Saskatchewan. This outbreak affected a total of two fields in the Birch Hills - Kelvington area in 1984. The disease went unnoticed until one day in July when a strong, warm wind produced a tangled mess of lodged plants. In many areas of these fields, the lodging was so severe that the plants lay flat on the ground. The most severely damaged field, which was seeded into canola stubble, had received a high rate of nitrogen fertilizer in the spring. Cool, moist early season growing conditions and the high level of available nitrogen produced a very heavy crop that was over 120 cm (4 feet) tall at the time of heading (cultivar Norstar). Grain filling was poor, harvest was extremely difficult, and yield losses were estimated at nearly 50 percent. The most noticeable features of this outbreak were its sudden appearance, the uniformity of damage over one 170 acre field, and the complete disappearance of strawbreaker foot rot as a disease problem in Saskatchewan from 1985 to 1996.
[ Images | Causes and Symptons | Losses | Control ]

c) Control:

Damage from strawbreaker foot rot has been primarily a historical note in Saskatchewan and no special methods of control are recommended. Excessive nitrogen levels favor this disease. Therefore, maintenance of a good nutrient balance may help to avoid a repeat of the important economic losses that this disease caused two farmers in the last 25 years.

Crop rotation to reduce inoculum levels, tillage practices that leave crop residues on the soil surface, and the application of fungicides are all important control measures that are used in regions where strawbreaker foot rot is a major disease problem.
[ Images | Causes and Symptons | Losses | Control ]

Figure 4. Strawbreaker foot rot (eyespot) weakens the stem making the plants more prone to lodging. Check for eye-shaped lesions at the base of the stem. (Image Size = 66k)