Spread out rotations | Spores can surviving for long periods in the soil
Soybeans’ honeymoon in Manitoba’s Red River Valley is ending and now the annoying relatives are beginning to visit and stay.
Soybeans are going to remain a popular part of the rotation in any area that can grow them, experts say, but farmers will begin treating them as carefully as any other prairie crop now that common diseases are showing up.
“Rotation: there’s no substitute for it,” Dennis Lange, an Altona-based Manitoba Agriculture farm production adviser, told St. Jean Farm Days in St. Jean Baptiste, Man., Jan. 4.
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“This year we’re starting to see some root rot, so those rotations are going to have to be spread out.”
Phytophthora, a common form of root rot in soybean-growing regions, has not become a big factor in Manitoba yet, but its appearance in a number of places in 2011 means farmers will need to get prepared for the crop to become harder to manage.
From almost no acreage a decade ago, soybeans have roared up the Red River Valley from the United States and taken over a large acreage of the rich valley land.
Almost 600,000 acres of soybeans were sown in Manitoba in 2011 and this year 700,000 acres are expected to be planted.
Short season varieties have allowed the crop not only to move to the northern end of the valley, but also up over the escarpment onto the western plains, with pockets of soybeans now being found from Winnipeg to the eastern half of Saskatchewan.
Farmers have been able to enjoy the benefits of the new crop with few of the crop’s usual problems, but crop advisers at Farm Days said the appearance of phytophthora root rot probably means farmers have been pushing their rotations and need to get back to good agronomic practices, with three to four years between soybean crops.
“It’s not widespread, but we’re starting to see it and once you see it you really have to be on top of it,” said Morris-area Cargill crop adviser Brunel Sabourin.
“Perhaps it’s a bit of a wake-up call.”
Phytophthora wasn’t the only type of root rot seen last summer, but it was the main one.
For some farmers, the disease’s problems didn’t appear during the saturated early part of the growing season, when problems would usually be expected to be noticed. Instead, they came later, during the dry second half of the summer.
That could have been a sign of the rot-afflicted root systems being unable to keep up with the plants’ water demand once the dry conditions set in.
Phytophthora is a family of diseases that afflicts everything from potatoes to oak trees to rhododendrons. Phytophthora infestans was the cause of the 1845-49 potato famine in Ireland.
Phytophthora sojae is the form that strikes soybean plants.
