Pathogen(s) causing disease:

Pseudocercosporella herpotrichoides

Symptoms:

Early spring symptoms of strawbreaker are elliptical or eye-shaped lesions on the leaf sheaths near the soil line. Lesions have light brown centers and dark margins. Lesions soon penetrate the leaf sheaths and expand until they girdle the stem. Patches of dull, charcoal gray fungus may be visible on the outside of the stems. Stem bases become bleached and brittle and break over between the bottom node and the soil line. This is similar to Hessian fly damage. Strawbreaker and Hessian fly can also be separated by looking at the stem bases. Hessian fly produces "flax seeds" just above the nodes. Strawbreaker produces dull, charcoal-gray patches of fungus on the lower stem. Strawbreaker does not cause root rot and severe stunting like take-all. Lodging is most common in the low, lush portions of fields where moisture and fertility are high. Lodging is usually multi-directional.

Strawbreaker can be identified by pulling a handful of tillers from the soil.  If roots pull out of the ground, then a true root rot is indicated.  If tillers break at the soil surface, then strawbreaker is indicated because strawbreaker weakens the bases of tillers causing them to break at the soil line while roots stay anchored in the soil.

Conditions:

 It survives at low levels on wheat or alternative grassy hosts. Inoculum takes several years to build up to damaging levels so strawbreaker is not a problem in first year wheat. Second year continuous wheat is sometimes affected and third year wheat is often severely attacked.

Spores are produced on old wheat residues during the late fall, winter and early spring. Spores initiate new infections on the lower leaf sheaths. Tillering seedlings are more susceptible than younger seedlings. The fungus is most active at 50°F. Infections are prevented above 60°F. Infections are favored by dense stands, high soil moisture, and high humidity.

Management:

Rotate out of wheat for a year - two years is better. Plant late - this alleviates strawbreaker by reducing stand density. There are no highly resistant varieties; however, stiffer-strawed varieties tend to resist lodging better than weak-strawed varieties. Fungicides are available. In contrast to these measures, practices such as excessive nitrogen and high seeding rates favor strawbreaker by increasing stand density. Burning and deep plowing stubble have no or little effect on strawbreaker.

Sources:

Kansas State University
Oklahoma State University