Crop analysts trying to root out the cause of unexplained low canola yields in Saskatchewan are on the trail of root maggots.
Fifteen years ago, root maggots became a problem in Alberta and Manitoba but were virtually unknown in Saskatchewan.
An Agriculture Canada study which surveyed crops over the past two years turned up shocking results about the number of maggots rooting through western Canadian canola fields.
“I don’t think maggots are the total answer to the problem but they certainly might be a contributor,” said Julie Soroka of Agriculture Canada.
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Emerge as pupa
Root maggots are small flies that overwinter as pupa and then emerge in the middle of spring to lay eggs, usually at the bottom of the plants.
The maggots burrow down toward the root and begin feeding as soon as they emerge from the egg.
The situation in Saskatchewan is less severe than Alberta, where canola crops are crawling with root maggots, Soroka told a soils and crops conference at the University of Saskatchewan Feb. 21.
Alberta Agriculture estimated losses to root maggot in Alberta in 1995 at $100 million.
Some areas worse
While the infestation and damage levels appear to be much lower in Saskatchewan, there are root maggot hot spots.
Of 240 fields studied in 100 rural municipalities in Saskatchewan’s Parkland region in 1995, all but one showed some level of root maggot infestation.
Only eight percent of the maggot-infested fields were less than 35 percent damaged, and 30 percent of fields showed up to 60 percent damage.
“This is quite dramatic in showing root maggot presence in Saskatchewan,” Soroka said.
The next year, 512 fields were surveyed in Saskatchewan in 182 rural municipalities with two to six fields sampled per RM from August to October.
Twenty-five roots were randomly sampled per field and shipped to the Saskatoon Research Centre for examination.
A 1995 survey showed 60 percent of roots infested had a 60 to 90 percent level of damage.
“This is only one insect and two years of data, but they are definitely here,” Soroka said.
Depending on location, maggots were detected in 30 to 60 percent of fields studied. The least damage was in the south. Close to half the fields in the Prince Albert region were infested, Soroka said.
Amount of yield loss
Researchers have not determined what level of damage causes yield losses in canola, Soroka said.
“If environmental conditions are favorable, canola roots can withstand considerable pruning,” she said. “If a drought occurs, any loss of root area may be detrimental.”
Across the canola growing regions of the Prairies, 1,088 fields were surveyed for root maggot presence and injury levels in 1996. Worse infestations are concentrated in the northern regions, but root maggots were found everywhere, Soroka said.
