This summer in Winnipeg 2 types of pesticides will be used to protect the trees in the city from a dangerous pest – the emerald ash borer.
This insect has caused significant damage to greenery in the city last few years. For the second year in a row, Winnipeg’s insect control branch will use 2 pesticides, including widely used neonicotinoid, to fight its invasion. This year, ash trees will be given three injections, created to minimize the effect of pesticides on other insects.
The plan of the city authorities is to destroy a sufficient number of larvae of this insect and to help the trees survive until the activity of emerald ash borers decreases. This should happen in the next few years, according to scientists.
"This is not just a one-time injection. Once you commit to a tree you've got to do it every two years," said Ken Nawolsky, the superintendent of Winnipeg's insect control branch. "So what's going to happen over the next five to 10 years is we're going to be looking at the trees that have been injected and comparing them to the trees that are adjacent that are not [protected], and determining whether the product was effective", he added.
2 pesticides are selected for use: azadirachtin, substance brought from southern Asia, and imidacloprid - one of the most common pesticides on the planet, which is neonicotinoid. In 2018, more than 1,000 ash trees were treated with these substances in Winnipeg.
Scientists say that it is very important to choose the right treatment time so as not to harm beneficial insects. Therefore, injections are carried out in the middle of summer, when the ash has already emitted its pollen. The mass extinction of bees throughout the world is associated with pollen contaminated with pesticides.
"Typically these treatments don't happen until sometimes mid-June, and so that is one way of preventing of exposure to bees," Nawolsky said of the tree injections. "The ash trees have already shed their pollen."
Richard Westwood, a forest entomologist from University of Winnipeg's, believes that there can be no harm from pesticides in the city, because they will not be sprayed, but will only be injected into the trees. He also noted that bees do not pollinate ash, wasps and some species of flies do this. Nonetheless, he thinks that the treated trees should be kept under surveillance in order to study the effect of these pesticides on other insects that feed on ash leaves, such as caterpillars.
"There could be a potential exposure," he said. "It would be a good idea to be taking samples of foliage or tissue throughout the summer just to see what the levels of the neonicotinoid is inside the tree."
The number of trees that will be injected this year is still unknown. Nawolsky noted that he still does not know what budget will be allocated for this in 2019. Last year, $1.3 million was allocated to emergency measures to combat this pest. This year’s budget should be submitted no later than the beginning of February.