Updated May 2021
The City of Lethbridge places strong emphasis on strategies to reduce chemical use and have adopted and implemented Integrated Pest Management programs to help control pests such as fungus, insects and invasive vegetation that threaten our urban forest and park spaces.
The Parks department continues to address pest management concerns and methods based on long-term objectives, environmental impact, human health and exposure concerns.
What is Integrated Pest Management (IPM)?
IPM is the balanced use of all available pest control methods. This includes combining approved chemicals and microbes, biological controls, and maintenance techniques. All available methods of prevention and control are utilized to prevent reaching damaging levels of pest infestation while minimizing chemical usage where possible.
A successful IPM program requires knowledgeable staff, a written plan, extensive monitoring of pest activity, appropriate cultural practices, accurate record keeping and being up to date on the most current information in regards to chemicals, insects, biological controls, plant diseases and weeds as well as recommended schedules, rates and applications.
Dandelions have been removed from weed control lists due to their abundance, resilience and positive impact to pollinator species. These plants provide an essential ecosystem resource as one of the earliest and most accessible sources of food for our local native pollinator species. Peak flowering is from March to May when pollinators are emerging from hibernation. Many other plants do not flower until later in spring or summer and are not as widely distributed as dandelions.
The City of Lethbridge is currently re-evaluating our dandelion management with the goal of creating an environmentally conscious and economically responsible, long term solution. Eradication is not practical and past control efforts have been costly. The parks department will be monitoring dandelion populations throughout the city and using the IPM to make decisions about control through plant density thresholds, location, timing and environmental costs vs. benefits. Dandelions will not be sprayed with chemical control while flowering in order to protect pollinator species.
Mosquito Abatement Program
The City of Lethbridge mosquito abatement program consists of treating standing water with larvicide each year. This is done by a full-time mosquito technician throughout the spring and summer. The larvicide is environmentally-friendly and does not affect mice, birds, fish, pets or other animals.
During a normal, dry season we may be successful in reducing populations by killing millions of larvae, which in turn do not become millions of reproducing adults. Wet spring conditions quickly overwhelm our efforts, in consistently rainy conditions, killing millions of larvae is not as successful simply because it generates too many small pools of standing water for us to efficiently treat.
We no longer spray for adult mosquitoes in Lethbridge for a number of reasons:
- Insecticide must contact adults to be effective and does not work when mosquitoes shelter beneath grass blades and leaves.
- Many beneficial insects such as ladybugs and lacewings are also killed by spraying.
- Acetyl-cholinesterase inhibitors (nerve blockers), the active ingredients in insecticides, are extremely toxic to humans.
Alberta Heath Services reminds Albertans that some mosquitos carry the West Nile Virus, so it is best to avoid being bitten at all.
- Use an insect repellent with DEET.
- Wear light-coloured long-sleeved shirts and a hat.
- Consider staying indoors at dawn and dusk when mosquitoes are most active.
European Elm Scale
European elm scale is an insect that attacks a variety of elm species. These insects feed on the fluids from the trees' leaves and inner bark. They produce a large amount of sticky 'honeydew' which eventually covers the leaves and bark in a black coloured mold. Heavy infestation may kill weakened trees and cause branch dieback in healthy trees.
In 2016, the City of Lethbridge began a campaign to combat the elm scale infestation treating approximately 3,600 public trees with TreeAzin (a natural insecticide) injections. The City remains diligent in the protection of the City's extensive elm population, and is implementing a rotational schedule of treatment for the estimated 5,500 elms located on public property.