For Home Lawns

The presence of a few weeds or insect pests in healthy lawns may not be cause for concern. If only a few weeds are present, removing them manually will ensure these plants will not spread further.

Keep an eye on pest problems and get more information if necessary before deciding on next steps. Regular inspection of lawns makes it possible to detect pests and other problems early.

Keeping an eye on developing pest problems will also help you decide:

• if treatment is needed
• when to apply appropriate teatments

Monitoring

There are several ways to monitor weeds on lawns and turf to determine if treatment with a pest control product is needed. Here are three methods for counting weeds to determine the percentage of weed cover on turf. They are from the Integrated Pest Management Manual for Landscape Pests in British Columbia. Once you choose a method, this same method should be used each time.

Transect Method: Use a rope or string to stake out a 10 m transect (straight line) through an average section of turf. Walk along the line and record the plants you see in a 10 cm² area at 10 points along this transect; check 10 or more transects per site. Averaging the scores from each type of site gives a percentage of weeds in the turf. Transect lines can be marked or knotted to show where to sample or you can pace along the length of the line and record the plants seen near your toe after each large stride.

Grid Method: Make a wire or wood frame, 1 metre square. Lay it down, randomly, on the turf and count all of the weeds inside the frame. Count at least 10 squares per site. Average the scores to arrive at a percentage of weed cover.

Centerline Method: Walk the centre of sports fields from goalpost to goalpost and estimate percent weed cover in a 10 cm² area at every second step.

Threshholds

Many provinces set treatment thresholds for the maintenance of lawns and turf. Here are some examples of pest population thresholds for different types of sites.

British Columbia

Integrated Pest Management (IPM) for weeds in turf is well developed in B.C. and the Integrated Pest Management Manual for Landscape Pests in British Columbia is used as a reference. Sites are categorized according to the maintenance level required.

• Class A (High level of service) sites are usually maintained as “weed free” turf and have only 5 to 10% weeds (5 to 10 per square metre). A common action level of herbicide treatment is 10 to 15% weed cover. Examples include fine ornamental lawns, golf and lawn bowling greens, and irrigated sports fields.

• In Class B (Moderate level of service) sites some weeds are acceptable, providing function of the site is not compromised, and weed coverage ranges from 20 to 50%. Examples include general park areas, residential and commercial lawns, boulevards, recreational fields, and golf fairways.

• Class C (Low level of service) sites are sites where control is needed to protect public safety (i.e. maintain sight lines, remove a fire hazard) or if noxious weeds are present or other weed populations threaten to contaminate nearby high value facilities. Acceptable levels are often around 50% weed cover. Examples include meadows, picnic areas, rough grass, undeveloped and naturalized areas.

Ontario

The Ontario Ministry of Agriculture and Food (OMAF) points out that it is important to remember that most thresholds are simply guidelines and that it is also important to consider the overall health and vigour of the turf when deciding if a treatment should be made. Treatment thresholds have been established for many common turf insect pests. Weed and disease thresholds are somewhat more subjective and should be established by the turf manager in consultation with the turf user group.

Turf IPM manual (Publication 816), along with
Turfgrass Management Recommendations (Publication 384) and Diseases and Insects of Turfgrass in Ontario (Publication 162) provides a complete reference package on turf IPM for Ontario.

Nova Scotia

The Nova Scotia Environment and Labour Ministry states that aesthetic criteria are usually used to set thresholds for pests of landscaped areas, turfed areas, or nuisance pests in buildings.