Professor Alan Watson

PHOTO: CLIFF SKARSTEDT

Pretty flower, deadly weed

PHILIP FINE | A McGill-led project in Mali aimed at ridding rural communities in Africa of the curse of a devastating weed is about to come to fruition.

When farmers in these regions spot a certain kind of bright pink flower decorating their fields of maize or millet, they shudder. They know it means that Striga is back to attack their crops and threaten their livelihoods.

Family members desperately pull out the weed as soon as Striga is discovered, but the damage has already been done, beginning long before the flowers ever appear.

Each weed yields thousands of seeds, condemning next year's crop to the virulent Striga -- leeching nutrients and stealing water from the cereals the farmers have been trying to grow.

"For some farmers, all they can do is move on to another piece of land," says plant science professor Alan Watson, the head of the McGill team fighting the weed.

Striga is the most serious constraint to sorghum, millet and maize production in the dry regions of the continent. It has been estimated that two-thirds of African cereal production is affected to some degree by the weed that wipes out up to 100 percent of some crops. The annual financial loss to Africa due to Striga is estimated at a staggering $10.5 billion.

The weed thrives in poor soil which shows decreasing plant diversity, conditions often experienced by poor farmers in dryland zones. What makes the weed tough to combat is the tens of thousands of seeds that each plant produces. Because of this prolific seed production, it can take years to clear an area of the threat. Some new herbicides and fertilizers can help fight the menace, but these are often not options available to poor farmers who can't afford them.

Watson and his group of researchers had a longstanding interest in biological approaches to weed control. Back in the early part of the decade, Watson's team established a top-quality containment facility at Macdonald Campus for testing different sorts of biological weed-killers.

"It's much like a high-level biological hazards lab," explains Watson. "It's very secure and tightly controlled. We bring in all kinds of different species here from around the world and we don't want things escaping that could be hazardous to Canadian crops."

The International Development Research Centre, which has been working on the Striga problem for years, heard about the facility and invited Watson to take part in the battle against Striga.

Watson and his fellow researchers began work on the project in 1991. They decided to look for natural organisms in African soil that could kill off the killer weed.

Watson's research assistant, Marie Ciotolo, headed up the hunt, travelling to Africa and identifying 100 potential enemies of Striga in the fields of Burkina Faso, Niger and Mali. Eight of them proved effective in attacking the weed at its source and one fungus, Fusarium oxysporum, which causes no harm to the cereals, was identified as the most deadly to the Striga weed.

Tests moved from the quarantined facility at McGill to a farmer's sorghum field in Mali and the results were phenomenal. Eighty-five percent of the Striga on the farm was wiped out at the seedling stage.

The McGill team, in cooperation with Mali's Institut d'économie rurale, has been evaluating the pathogen in farmers' fields in Mali since 1994. Fusarium oxysporum is now produced on a larger scale through a fermentation process and is applied in a powder form as a coat on sorghum seeds.

Last year, a collaboration was initiated with a group of scientists from Université Laval, led by Alain Olivier, to test the efficacy of the fungus under different agricultural conditions. "Increasing the fertility of the soil makes a great deal of difference in our ability to reduce Striga," says Watson. Fertile ground gives Fusarium oxysporum an important advantage in its war on the weed; Striga is at the height of its powers in dry soil.

Field trials done by graduate student Annie Letourneau will be conducted to examine the effect of intercropping sorghum with legumes, as well as to see what effect the newly grown Fusarium oxysporum has on Striga growth.

Also, this summer, McGill PhD student Roger Maclean produced a socio-economic study that evaluated the feasibility and the adoption of the project.

One of Maclean's recommendations -- which dovetails with the IDRC's focus on supporting women in developing countries -- is to make female villagers partners in the distribution of Fusarium oxysporum. "Basically, the women would be selling this technique to their husbands," says Watson, giving female villagers a greater measure of autonomy.

By next year, the scientists will have more conclusive findings on the effectiveness of the fungus.

One of the best aspects of this discovery has been the fact that Fusarium oxysporum can be grown by farmers themselves. Once they're shown how to do it, farmers will be able to produce the dried fungus, which can be stored for months without any measured lessening of its effectiveness.

And it is hoped, once it's in their hands, they will be spreading it on fields that will not turn into pretty pink meadows, but will be rich in food that sustains them, their families and their neighbours.