Weed Control and Plant Disease

Weed Inspection Program

The three classifications of weeds:

1. Restricted weeds: Must be destroyed, including Nodding Thistle, Eurasian Water Milfoil, Diffuse, and Knapweed.

2. Noxious weeds: Noxious weeds are very aggressive and damage both lawns and agricultural fields. These weeds must be controlled to prevent further spread. Physical removal is often the best option; however, there are herbicides that may help. It is very important not to compost noxious weeds. Some common noxious weeds include:

Scentless Chamomile

Attractive daisy like flowers 2 to 3 cm across; grows from 15 cm to over 1 m in height; fern-like, very finely divided leaves, blooms all summer. When leaves are crushed, they are scentless.

Perennial Sow-thistle
A creeping rooted perennial growing 0.4 to 1.5 m tall; stems branch near the top; leaves with weak marginal prickles clasp the stem; plants contain a bitter milky juice; upper stalks and flower bracts usually covered in gland-tipped hairs; yellow flowers up to 3.8 cm broad.

Canada Thistle
Creeping rooted perennial growing erect to 1.2 m; stalkless dark green leaves with irregular spiny lobes; flower heads spineless and small compared to other thistles; flowers variable in colour from rose-purple to pink to white.

Toadflax
Creeping rooted perennial to 0.6 m tall; the stalkless leaves are narrow and pointed at both ends; bright yellow “snapdragon-like” flowers with an orange spot on the lower lip are 2 to 3.5 cm long centres.  No milky juice tin plant.

Oxeye Daisy
Rhizomatous perennial growing erect to 1 m in height; lower leaves spoon-shaped, coarsely dissected and stalked; upper leaves narrower and stalkless or clasp the stem; daisy-like flowers borne at ends of stems; central yellow disk flowers 10 to 20 mm wide; white ray flowers are 1 to 2 cm long often confused with the ornamental Shasta daisy.

3. Nuisance weeds: Do not have to be controlled. These include Dandelions and Quack grass.

Weed Complaints

The Parks Department is responsible for identifying restricted and noxious weeds.

Once a weed complaint phone call or letter is received for weeds on a private property, the Parks Department will:

1. Complete a site inspection by the weed inspector to determine types of weeds and if they are required to be cleaned up as prescribed in the Weed Act.
2. A notice is sent directing the owner to either destroy all restricted weeds or control noxious weeds. The property owner is normally given two weeks to control noxious weeds. If the property is not cleaned up, a private contractor cleans up the weed, which is then billed back to the property owner’s taxes.
3. To avoid being served with a notice, property owners are asked to ensure vacant lots are maintained, and if you are on holidays make alternative arrangements.

Dandelions (Broadleaf Weed Control)
The City of Airdrie sprays dandelions on an “as needed” basis. The Parks Department has different tolerance levels for maintainence.

For example, parks such as sports fields, preventative maintenance will continue as normal, but once dandelions exceed a total area of 10 per cent, then an assessment is undertaken to determine what type of control is required. A sports field is monitored by selecting six areas and estimating the overall weed density. If weeds exceed the set tolerance level then control is initiated. The City’s goal is not to reach these thresholds.

If you have any questions or concerns, e-mail the Parks Department at parks@airdrie.ca or call the office between 8 a.m. and 4:30 p.m., Monday through Friday at (403) 948-8400.

Pesticide Use Programs

The City will post a notice when pesticides are to be used in a public area 24 hours in advance. A sample of notice for the Pesticide Program which you may see in your community:

This is to notify the City of Airdrie intends to conduct pesticide control programs as necessary. Control programs may include weed and insect pests (in accordance with Pesticide Service Registration) issued by Alberta Environment for Landscape No. 1481-02-00.

Plant Diseases

Blackknot
Affects mostly fruit trees. Small light brown swellings occur on branches. Initially the knots are 1 to 2 cm, by autumn they turn black and harden. Control by removing affected branch 10 cm back from the knot.

Fireblight
Trees and shrubs in the rose family are affected. Infected blossoms suddenly become brown; later on young shoots appear scorched by fire. Control by removing the affected branch 20 to 40 cm below the branch.

Cottony Psyllid (Psyllopsis Discrepans)
Cottony Psyllid is a European insect first noticed in the Edmonton area in 2000, and has since been observed in other locations including the Airdrie area. It is most severe on trees undergoing drought stress.

Control of this insect is difficult due to the lifecycle of the insect and the protection the curled leaves provide.

These Cottony Psyllids attack black and Manchurian ash, but not green ash.

These insects overwinter as eggs attached to outer branches. In the spring, the young Psyllids, which resemble aphids, hatch from the eggs and suck sap from the leaflets. This feeding causes ash leaflets to become shrivelled and discoloured as shown in the photograph. The leaflets curl under from the sides to enclose the Psyllids and a white, cottony material they produce.

Trees that are well watered appear to suffer less damage from Cottony Psyllid. Insecticidal soap is a less toxic product registered for the control of Psyllids.

For more information, please call (403) 948-8400.