“If you’ve ever seen fleas on a dog, how they jump and go crazy – that’s how these things move”
– Nancy Gray, Iaps Co-Ordinator For Eastern Saskatchewan
The best things in life are free, they say. That includes leafy spurge beetles.
A bug net, a paper bag, a cooler and some ice packs are all you need to collect Mother Nature’s answer to the scourge of leafy spurge, according to Nancy Gray, an invasive alien plant species co-ordinator for eastern Saskatchewan.
Next, you need to find a good spot for collecting adult spurge beetles. There are many different varieties that have been brought over to North America from Europe and Asia to devour the pesky weed, but the best for the Prairies are Aphthona lacertosa, commonly known as the black spurge flea beetle, and Aphthona nigriscutis, although copper in colour, is known as the black dot flea beetle.
The black beetles tend to do better north of the Trans-Canada Highway, while the black dot beetles seem to work better in the south, she said.
“Anywhere there’s a lot of trash cover, we’re finding that the black beetles are the best bet,” said Gray, in a presentation last month at a seminar for the Leafy Spurge Stakeholders Group hosted by Brandon University’s Rural Development Institute.
There are about four sites in Saskatchewan where collection parties are organized each year, but a section of land near Weyburn at Maxim, Saskatchewan, where the beetles were first released in 1991, is the best known.
Since then, the beetles have wiped out much of the spurge and the grass has come back, and the collectors are having to range further to find the best spots.
Like most biological control agents, the beetles always save 10 to 15 per cent of the spurge for the next generation, so they are best considered as a tool for restoring a balance rather than full eradication.
“It’s going to suppress the population, but no beetle wants to take its food source and throw it away. They’ll never take it to zero,” she said.
The best time to catch them is between the third week of June and mid-July, on a hot day with no wind, according to Gray. Sweep the net back and forth along the tops of the plants to scoop up the mature beetles.
“July 15 is kind of the cut-off. Because if you sweep and then release them after that, they didn’t lay any eggs or the eggs were nonviable the next year,” said Gray. “You can go out and monitor the area for adult beetles, but don’t move them after that time.”
A minimum of 1,000 beetles is recommended per release, preferably near the edge of an area with heavy spurge infestation and full sun exposure, such as a south-facing slope. For moving beetles short distances, such as within a field, just leave them in the net and dump them out in the new spurge patch.
A stake should be driven at the spot where the beetles were released, so that progress at the site can be monitored. That way, if a population explosion results, more beetles can be collected and moved to another area.
The real work of spurge beetles happens underground, she said, where the larvae attack the extensive root systems and weaken the stand. Results can be easily seen in an ever-expanding halo of dead stalks or stunted plants around the release point, like a bomb explosion in slow motion.
Beetles can be used in conjunction with spraying in the fall after the bugs have quit for the season, because the weakened plants are more susceptible to other control measures. Grazing with goats or sheep also helps, provided that the animals leave enough spurge for the bugs to thrive.
Harvey Anderson, who is IAPS co-ordinator for western Saskatchewan, said that for best results, bugs should be collected at a similar latitude or less than 100 kilometres away from the intended release site because even slight variations in climate can hurt the bugs.
“We’ve collected them in North Dakota, right along the Manitoba border. That’s not a bad jump. But moving them from Weyburn to Dauphin, for example, might be a little bit too far,” he said.
Most first-time collectors head straight into the sea of yellow with their nets, but Anderson said that the best collection spots tend to be where the spurge is thinner and not flowering on the fringe areas.
Using airtight plastic bags for transporting beetles is a no-no, because the bugs will suffocate. While collecting, be sure to keep the bugs cool, such as in the shade of the truck, because they can’t stand high temperatures for long periods.
Duct tape should be used to carefully seal the openings on the paper bags.
“These little buggers get out of everything, said Gray. “If you’ve ever seen fleas on a dog, how they jump and go crazy – that’s how these things move.”
On the way back from a collection trip in the United States, a sleeping colleague accidently bumped open a container of beetles. The beetles swarmed all over the passengers and the vehicle. They made it through customs, but later Gray was pulled over by a police officer.
“This young cop comes up to me, takes one look at the truck and at me, then takes a step back. I’m sure he thought that I was covered with fleas, because there was all these black beetles jumping out of the window at him,” said Gray.
The Saskatchewan Sheep Development Board has been grazing sheep near Saskatoon with good effect.
Grazing with sheep works, but the first two or three years may seem like it is making the problem worse. That’s because the stress of grazing makes the roots put up more plants. But over time, the spurge uses up its stored reserves, and is never allowed to set seed. [email protected]