They’re a scourge on the local ecosystem, but the battle against invasive plants in Burnaby appears to be tilting toward the city.
This week, the city’s environment committee received an update on Burnaby’s invasive plant management strategy for local parks.
Overall, the report noted all invasive plants in treatment areas are showing reduced growth and spread, and in some cases there has been no regrowth for more than two years.
In 2009, the city began its invasive plant management both with an invasive plant survey and habitat management strategy.
The survey identified and prioritized key species and locations to manage, while plant management targeted the removal of specific species in all parks: the Butterfly bush and Pickerelweed.
Five more species were targeted for removal or control of spread but not total eradication.
The city noted the approach has been used at Cameron Park, George McLean Park, Taylor Park, Jim Lorimer Park, and Warner Loat Park, while Central Park and Deer Lake Park are larger parks where continued efforts are ongoing.
In terms of the Butterfly bush, the report noted by 2014 a majority of sites showed no evidence of re-growth or new seedlings.
With the Pickerelweed, infestations at Deer Lake Park and Fraser Foreshore Park were relatively small and removed by hand. In 2014, only one site at Deer Lake showed re-growth. Seven sites have shown no-regrowth for three or more years.
In the case of the Japanese knotweed, initial treatment of manually pulling the plant proved to be ineffective.
In fact, through the disturbance of pulling plants, the knotweed infestations spread.
The city then tried a herbicide treatment trial in three parks using a stem injector gun with glyphosate to treat each stem of the infestation.
The herbicide resulted in 50 to 100 per cent mortality in the treated plant.
In 2014, the city turned to the use of foliar spray application against the knotweed to treat areas adjacent to park lands. Foliar spray allows treatment of the stems too small to be treated by stem injection.
The city report noted the foliar spray makes it possible to treat 100 per cent of the plants in the infestation at one time, with 36 of 111 sites showing 100 per cent mortality.
“Through adaptive management, all invasive plants in treatment areas are showing reduced growth and spread, and in some cases, there has been no regrowth for over two years,” the report stated.
City staff have recommended to continue the program for next year.
