Manitoba has been using biocontrol beetles since 1988 in Spruce Woods Park, but the results haven’t been encouraging.
In the 1990s, there were 3,500 beetle releases, mainly the black and brown flea beetle species, said John Johnson, president of the Manitoba Weed Supervisors Association. In 1996, 350,000 were brought in from a capture site in North Dakota.
But because most leafy spurge infestations in Manitoba are found in areas with sandy soils, the program hasn’t been as successful as in North Dakota, where soils are heavier and spurge tends to have shallower root systems about four to five inches deep. Also, the terrain in Manitoba is less open and shaded by bush and trees, which trap moisture that the beetles don’t like.
“The root profile here goes straight down into the water table and they don’t have as much root to survive on as in North Dakota,” said Johnson. “There are success stories out there, but they haven’t been the answer for us yet.”
Beetles can still be found at the release sites, he added, but they are not having the same impact as they did south of the border. Numbers released, at anywhere from 250 to 350 per site, were much lower, but in some places up to 5,000 were released at “nursery” sites.
Five more species of spurge beetles are known to exist in Eurasia that might work here, but the cost of importing them could be as high as $1 million to bring even small numbers over.
Cheryl Heming, co-ordinator of the Invasive Species Council of Manitoba, said that a trip to North Dakota to collect beetles is being organized for early July, and landowners are welcome to contact her to come along. Contact: [email protected] [email protected]
– JOHN JOHNSON