SPRUCE HOME, Sask. – As Garry Bowes’ truck rolls down the dirt road, it occasionally passes tiny bushy plants sporting pretty white flowers.
Each plant grows between the grass of the ditch and the packed mud of the road, seemingly so weak that it can only cling onto the periphery that more robust plants have scorned. As the truck passes, the white petals disappear under a carpet of dust.
But not from Bowes’ mind.
The integrated pest management specialist with Saskatchewan Agriculture is one of the soldiers fighting a desperate battle to slow scentless chamomile’s invasion of Western Canada.
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They freely admit they’ll never entirely eliminate this new crop enemy.
“Once it’s there, it’s there,” said Bowes, who has come to this area northeast of Prince Albert to check a new weapon against the noxious weed.
Left unchecked, scentless chamomile can become a perennial problem and swiftly take over entire fields. But Bowes thinks farmers can tame the pest if they are diligent.
He and other agrologists are trying to develop a package of methods that will minimize the weed’s impact. It involves diligent observation, immediate action, preventative measures and chemical and natural controls.
“There is a potential for really catching it,” said Bowes.”You can keep it off your land for a long time.”
From Europe
Scentless chamomile, like most pioneers and invasive prairie weeds, is a European immigrant. It probably arrived as an ornamental flower.
It thrives in typical weed-friendly conditions: disturbed soil, weak competition and neglect.
Scentless chamomile tends to spread from road edges, where passing trucks, mowers and other farm machinery scatter its seeds. It doesn’t spread easily across an undisturbed ditch, where well-established grass crowd it out.
But the dangers are extreme if the weed can cross the ditch and get into the fringe of a farmer’s field, where plowed soil offers the perfect home.
Often the weed will first infiltrate along the fringe between the seeded crop and the ditch grass. This creates a strip of white flowers along the perimeter of a field that some farmers call “the bathtub ring.”
The weed will grow and flower during the season. Each plant can produce hundreds of thousands of seeds.
Harvesting equipment easily spreads multitudes of seeds across the field. Weed seeds mixed into common seed can make pollution universal. The next year, the farmer may find nothing but a sea of white flowers where he expected to see a crop.
Agrologists suggest several farming practices that can rob the weed of its beachheads.
It’s important to make sure there’s no fringe of tilled but unseeded soil between the crop and the grass.
It is essential to clean all weed seeds from equipment. Grass mowers can transport seeds miles down a ditch.
Roadbuilders must ensure that when they tear up a ditch with their equipment that they immediately reseed the disturbed soil to grass.
Farmers must act if scentless chamomile appears in the ditch beside a field, or on the edge of a field.
It means getting out of the truck.
“If you see it, pull it,” said Bowes. “It’s a lot of work.”
The tops of the weed can also be mowed before the plant sets seed, but this does not kill it and repeated mowings may be necessary.
It is susceptible to some chemicals, but not to the cheap and easy solution of 2,4-D and Dicamba, to which it is mainly immune.
Industrial-strength applications of chemicals such as Ally and Lontrel are allowed along roadsides and can be effective.
Bowes has high hopes for bio-control methods.
He said farmers will have much better overall control of the weed if these new methods can cripple a significant proportion of the crop.
Because scentless chamomile is an imported species, it has almost no native pests to damage its performance. There’s little that holds it back if it gets into favorable conditions.
Bowes and other researchers have been testing a number of bugs that may bring the weed under control, creating a new, sustainable equilibrium.
An imported seed weevil has proven effective at crawling into seed heads and chewing its way through seeds. The weevil can overwinter and its populations are expanding slowly.
But with each weevil eating only about 11 seeds, and each plant producing thousands of seeds, the weevil is unlikely to eliminate the threat.
Another insect, stem borers, dig into the plant’s stem and eat through the plant, reducing its vigor and ability to produce seed.
However, establishing the bug is a problem, and researchers will need to get many populations established before judging its effectiveness.
The gall bug is the one Bowes is checking on this dirt road.
The adult midge, which flies from plant to plant, burrows into a scentless cham-omile plant and lays an egg. As the pupae develops it forms a gall, or swelling, around the developing bug. It appears to make the plant go haywire, causing a green clump of leaves to develop around the pea-sized gall. The plant is crippled, seldom growing much beyond the point of the gall.
This day, Bowes is driving to a field owned by Rod Sexsmith, where the gall midge is being tested. Though there are a few scentless chamomile plants growing along the edge of the dirt road, the real problem is inside the field, around a small slough.
There, the “bathtub ring” is obvious. The weed, which thrives in wet conditions, stands all around the edge of the depression. This year, the land was farmed close to the edge of the slough area. In one place machinery actually cut through formerly untilled land and scattered some weed seeds.
This newly tilled soil is rife with tiny scentless chamomile plants, which will grow as winter annuals this year. They look like miniature green ferns and seem harmless. Next year it will be a different story when they grow out and spread their seeds.
It’s a classic case of scentless chamomile spread.
But Bowes’ gall midge control also appears to be working. He and Prince Albert agrologist Barry Swanson drop to their knees to check the weeds and repeatedly find galls on stunted plants.
Hoping for a solution
This year Bowes transplanted some midge-infected plants into the slough, and the midge appears to be spreading.
If this new form of bio-control works, Sexsmith will be happy.
“We picked and picked and picked and burned and burned and burned,” said Sexsmith, who has so far been frustrated in his efforts to get rid of the weed.
Other farmers would probably be happy as well.
Most Saskatchewan RMs are infected, Bowes said. The situation is similar across the Prairies. But while some farms have only sporadic patches along a few roads, others, notably in southeastern Saskatchewan, have the weed everywhere.
In Sexsmith’s area, the weed is just now becoming a problem.
“This is one of the frontiers,” Swanson said.
Bowes said the key to fighting a weed like scentless chamomile is not to concentrate on inventing a magic bullet solution that will eliminate it.
That’s not likely to be discovered.
But using a package of good farming practices, vigilance and natural controls may stop it from becoming a crop-destroying plague.
