How To Tackle Pasmo On Flax Crops

Flax isn’t a high acreage crop, however it’s a relatively common oilseed grown in rotation in certain areas, such as Manitoba and southeast Saskatchewan. Flax has been seen as an alternative to canola to diversify oilseed rotations as it is often thought of as a less intensively managed crop. There is one common complaint among farmers growing the crop, and that’s its relatively static yield potential. Many growers report that their average flax yields have been static for decades, often yielding in the low 20 bushels per are range.

Part of the static yields can be attributed to differing agronomic practices and limitations. Growers routinely save their flax to be the last seeded on the farm. As with other crops, yield potential is diminished the later the crop is seeded. Most growers agree that something has to be seeded last and that often because of yield potential and harvest management, flax is often a good option for that.

PASMO

The presence and detection of the disease pasmo (Septoria linicola) has been increasing. According to Agriculture and Agri-Food Canada, pasmo was observed in 90 per cent of all flax crops surveyed. Breeding for resistance to pasmo is in the early stages, but varieties that are currently grown are susceptible to the disease.

Pasmo attacks the above ground portion of the flax plant. It often over winters in the soil on plant residue, although the incidence and movement of the spores does increase with favourable weather conditions such as higher temperature and moisture.

SIGNS AND SYMPTOMS

The visual symptoms of pasmo are circular brown lesions on the leaves. As it progresses, brownish black stripes or infected bands occur on the stem. The brown bands alternate with healthy green bands, giving rise to the term “tiger stripe.” Unfortunately, these visual symptoms do not show up until after the damage of pasmo has occurred and the treatment window has passed.

Pasmo weakens the flax plant and causes defoliation, resulting in premature ripening and yield loss. As well, the pedicel of the flax is also weakened causing increased boll drop in windy or wet weather conditions.

MANAGEMENT OF PA SMO

Pasmo can be managed by a combination of cultural practices along with the application of a fungicide. Seeding date can play a role in disease severity. The earlier flax is seeded the healthier and more vigorous it is; a healthy plant can better handle the onset of the disease. Keep three years between flax crops to minimize the amount of infected residue that may introduce the disease.

Even with crop rotations, if weather conditions are favourable for the disease and the crop potential looks promising, it is safe to say that in traditional flax growing areas, pasmo is prevalent. Farmers have seen tremendous yield results by spraying their flax with a fungicide treatment of Headline, a BASF product.

The recommended spray timing is during mid to late flower, or about seven to 10 days after the onset of flowering. The crop will be well into bloom and will look quite blue during the mornings at the proper spray time. Headline should be applied at 120 ml per acre or about 40 acres can be treated with one jug. Coverage of the plant is very important for control of pasmo; the recommended water volume is 10 gallons per acre (gpa) for ground application, but our farm has had better results using 12 gpa.

Yield differences can vary depending on the level of disease present. Jay Gerry who farms near Griffin, Sask., has sprayed Headline on his flax crop for the last three years. In 2008 he noticed a 21 per cent increase in yield. Gerry says that visual differences between sprayed and unsprayed areas of the field were evident. “Straw where the flax wasn’t sprayed was brown and it was visual as the disease was rotting the straw.” he says. There was a visual maturity difference as well, as the pasmo caused premature ripening of the untreated crop. He also noticed a visual size difference to the bolls which was obvious from the combine cab.

Bobbie Bratrud owns and operates Bratrud Ag Advisory Services (www.bratrudag.ca)with her husband Mark. They also farm at Weyburn, Sask.

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