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A Helping Hand

A Canadian Forest Service research project looks at a natural way to control unwanted vegetation on planted sites.


by Jim Stirling
Copyright 1998. Contact publisher for permission to use.

Developing a fungus that targets unwanted vegetation on planted sites is an intriguing and expanding field of research. lt is designed to provide commercial tree seedlings with a faster and healthier transition to the free-to-grow stage. Think of it as helping Mother Nature tip the balance toward crop trees.

Enhancing the effectiveness of a natural enemy to the unwanted species is also ecologically, environmentally and operationally sound, believes Dr. Simon Shamoun, a research scientist with the Canadian Forest Service at its Pacific Forestry Centre in Victoria, BC.

Dr. Simon Shamoun

Dr. Simon Shamoun, a research scientist with the Pacific Forestry Centre in Victoria, BC, is working with scientists from other forest research labs and regional forest companies on developing a fungus to suppress unwanted species competing with coniferous seedlings.

The goal is to apply a naturally occurring fungus to suppress unwanted species competing with coniferous seedlings for nutrients, water, space and light. Many of the most productive growing sites have the greatest potential for competition from unwanted vegetation. The fungus will not eradicate the weed species but instead opens a needed window to accelerate crop tree growth."It's a more sound approach to look at the total picture. We have to preserve the ecosystem and the ecology of the plants. We have to interfere in a natural way," summarizes Dr. Shamoun.

He terms the fungi his team are identifying and formulating as biological control agents. Dr. Shamoun is coordinator for the Biological Control of Forest Weeds Project. It is a national initiative, involving forest research labs at the CFS's Northern Forestry Centre in Edmonton, Alberta; Great Lakes Forestry Centre in Sault Ste. Marie, Ontario, and the Atlantic Forestry Centre in Fredericton, New Brunswick. The research includes a growing involvement from regional forest industry companies.

Dr. Shamoun says alternative methods of vegetation control have accompanying drawbacks. "The use of chemical herbicides has some adverse environmental effects, primarily on small organisms, and if it is not used at the right time can damage crop trees. It's also very expensive. There's a lot of pressure from the public and other agencies for alternative methods that are environmentally acceptable and economically feasible,"

He also notes British Columbia's Forest Practices Code restricts the use of herbicides around riparian zones. Dr. Shamoun agrees manual brushing can be effective, but cutting back unwanted species merely encourages their growth. "They respond more vigorously because of a root system very rich in carbohydrates."

Using sheep for vegetation control involves moving, managing and guarding the animals. Sheep can also damage crop trees and they find some weed species unpalatable. Dr. Shamoun says the three major targets for biological control agents are on hardwood weed species in conifer reforestation sites and right-of-ways; on the Rubus family of plants and on unwanted grasses. The most advanced is the fungus for hardwood weed species. Dr. Shamoun estimates the commercial use of the patented ECOclear product is a year away. "It will be the first biological product of its kind on the market in North America," he predicts.

It has been a painstaking 14-year process of discovery and formulation for the phytopathogenic fungus Chondrostereum purpureum to be primed for operational use. The naturally occurring fungus is formulated to invade fresh wounds or cut stumps of the invasive red alder. Extensive greenhouse screenings and field trials have proven the fungus works, says Dr. Shamoun. His colleague, Dr. Raj Prasad, coordinated the national field trials and collaborated with the project's other partners. Dr. Prasad is also assessing the impact of Scotch broom on conifer plantations and other plant communities.

Dr. Shamoun says developing Chondrostereum purpureum was a very rewarding experience for the team. "It paved the road for other biological control agents. We have this model system. We know the problems associated with the development of other agents and know exactly how to overcome them."

The most immediate beneficiary will be the fungus formulation to combat the herbaceous members of the Rubus family. It is in the development stage and if all continues to go well, will be available to industry within seven years, predicts Dr. Shamoun. The Rubus family plants in BC flourishing on replanted and burned forest sites are thimbleberry (on the coast and in interior); salmonberry (coast sites only) and wild red raspberry (in the interior). The biological control agent identified to do the job on Rubus is a fungus called Fusarium avenaceum. It was developed by Dr. Shamoun and Carmen Oleskevich, microbial control technician at the Pacific Forestry Centre.

Again, the research team's philosophy is not to eradicate Rubus. Rather, the fungus is applied to raise it from naturally endemic levels to epidemic levels. After the Rubus plants are curtailed, the fungus reverts to its normal level. During the process, crop trees acquire the competitive edge. The host-specific fungus leaves conifers unharmed.

Dr. Shamoun's team is investigating the byproduct toxins produced in the fungus. DNA finger printing techniques will also be employed to detect the genetic versatility in the Rubus profile to customize the biological control agent fungus accordingly. "We have to look at the whole picture for developing these agents," reminds Dr. Shamoun.

He expects the commercial version of the fungus to be applied with a backpack spraying unit similar to that used for chemical herbicides. "Ultimately, if all goes well, we will be able to aerial spray."

The biological control approach to vegetation management is an appealing one to Paul Kutz, area forester with MacMillan Bloedel's Stillwater Logging Division in Powell River, BC. "I've talked with Simon (Shamoun) and I've done some reading on the subject and I'm very keen on trying different methods," he explains.

The Stillwater Logging Division has taken an integrated approach, combining a large brushing program and the use of sheep and herbicides based on area and urban interface, says Kutz. Hardwood alder and salmonberry are major problems on the company's growing sites

"We can't use herbicides in some riparian zones yet under our pre-harvesting prescriptions we're responsible for seedlings to free-to-grow-stage." Kutz says manual brushing can cost $600 - $800/ha while early indications are that applying biological control agents may cost about $400/ha. "If it's effective, we're looking at major cost savings to the company."

The Pas Lumber Co Ltd., of Prince George, is another company following the research with interest. "Thimbleberry and red raspberry are major concerns in many of our growing sites," confirms Peter Forsythe, a forester with The Pas. The company has tried vegetation control methods like sheep and manual brushing.

"Biological control is in its infancy. It does not kill the Rubus plants just sets them back. It's the more natural way."

The Pacific Forestry Centre's Dr. Richard Winder and Donna Macey are examining potential biological control agents to target grasses on coniferous planting sites. Developing fungi and bacteria to manage grasses is in the discovery and development stages, reports Dr. Shamoun.

The team's cumulative research into biological control agents is more than academically fascinating. It offers the forest industry realistic and natural answers to pressing vegetation management problems with implications for healthier young forests and increased fibre throughout Canada.


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