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Lawn pests in Calgary

A healthy lawn is a beautiful thing – make sure yours stays healthy and vibrant by watching for signs of two common pests: Fairy Rings and Dew Worms.

Fairy rings

Fairy rings are caused by a fungus that is particularly noticeable and damaging in drier locations, with lighter soils and lower fertility, including some soils in Calgary.

Signs and symptoms of fairy rings:
A ring of mushrooms followed by rings of darker green grass with an inside border of dead grass is one sign of fairy rings. Small tan-coloured mushrooms usually develop on the outer border of the ring especially during rainy weather or later in the season, but these mushrooms should not be confused with the cluster of mushrooms that commonly appear in the lawn after heavy rains or mushrooms that are caused by old decaying root systems.
Controlling fairy rings:
Proper lawn care and maintenance are the first step to preventing this pest. Although the fairy rings are caused by fungi, there are no fungicides that will control the mycelium, or underground growth of the fungus. A root feeder or garden fork should be used to make holes throughout the ring area. The holes should be 10 inches (25 cm) deep and 4-6 inches (10-15 cm) apart. This area should then be soaked every second day, if not every day, for at least a month, especially if the fairy ring had progressed to the dried grass stage. A teaspoon of liquid dish detergent in a gallon of water can be sprayed on the surface before watering. If only a few rings are present in the lawn it may be practical to excavate the affected area by removing the turf in the area of the ring along with the surrounding 18 inches of soil on both the inside and outside of the ring. The soil should be removed to a depth of at least 2 inches (5 cm) below the zone of the white fungus mat.

The fairy rings will tend to die out when they encounter sidewalks, flower beds and other cultivated areas.

Dew worms

Dew worms – also known as night crawlers – are large earthworms that are active at night and during rainy weather, and can vary in size from 90-300mm in length. While most earthworms are advantageous to have in your soil, dew worms are not as popular. After a rainfall or lawn watering, dew worms excrete small, uneven mounds of clay that can make lawns unsafe to walk upon and more difficult to mow.

Controlling dew worms:
Since dew worms live under lawns, patios, flowers and vegetable gardens, they’re impossible to completely get rid of. However, the robins, snakes, toads, moles, foxes, beetles, centipedes, leeches and slugs are all predators of the dew worm. The most recognizable natural enemy of dew worms is the Robin.

No chemical controls have been developed that specifically target dew worms, but to eliminate mounds of castings, spread gypsum (calcium sulphate) over the castings. When this harmless chemical is spread over the affected area, watered and allowed to dry, the clay will become crumbly. Dew worms do not like abrasive soil materials, so consider topdressing your lawn with a course sand mixture after aerating your lawn.

For more information, visit our YardSmart.