A variety of insects in Colorado can do varying degrees of damage to the lawn. Chewing and sucking insects on the surface can damage the blade, sheath and crown while subsurface or soil insects feed by chewing on the grass roots. These insects need to be treated uniquely at different times of the year and can require a high level of knowledge to diagnose the damage and apply the proper insecticide. Elk Creek will inspect, diagnose and eradicate any insects on the lawn to get your lawn growing, healthy and green again.
Turf mites are very small insects which feed on the blade of the grass. Common types found in Colorado include Clover Mite, Banks Grass Mite, Banks Grass Mite, Brown Wheat Mite and Winter Grain Mite. Most turf damage from Mites in the Front Range area is caused by the Clover Mite. These insects will pierce the turf blade removing chlorophyll and cell juices causing grass to appear silver or yellow. Injured turf often occurs near vertical surfaces as the Clover Mite will leave the grass to lay eggs on areas such as foundations and rock walls although damage will also occur in very dry areas of the lawn by borders and under evergreens. While generally not considered a serious pest, most damage occurs from late Fall to mid-Spring during very dry conditions. A topical insecticide applied to the grass during these dry periods will help to control mites and added fertilizer for damaged areas will speed recovery. Clover Mites are not a problem during the growing season provided that the lawn is regularly watered as mites cannot thrive in a wet environment. Although rare in the Front Range, other piercing insects occasionally seen in the lawn include Aphids (Greenbugs), Chinch Bugs and leaf hoppers.
Surface Chewing Insects:
Sod webworms are the larvae of adult moths and their life cycle includes the following stages: egg, larvae, pupae and adult with turf damage occurring during the larvae stage.
The larvae are identified by a double row of brown or black spots down the back, located at the base of long bristles. The larvae spend their day in silk lined burrows from which they emerge at night to feed on the grass blades. They will also deposit frass by their burrows, dark green fecal matter which will help with identification. The chewing activity of the webworm removes the tender the new growth from the top of the blade leaving shorter stressed areas of turf. The worst damage occurs in July and August and is often mistaken for drought stressed turf which has entered summer dormancy. As the larvae do feed mostly at night, any insecticide treatment should be applied late afternoon to evening for the best control of sod webworms.
Cutworms receive their name from the feeding habit of cutting off blades close to the ground. These are also larvae of adult moths and also have the full life cycle. Brown, gray or black in appearance about 1.5-2” long and with black and bronze cutworms having stripes down their back. These large, mostly hairless larvae feed at night on the base of the grass blade and will also leave frass by feeding sites. Late April and early May are the times of heaviest damage in eastern Colorado and will be seen as closely chewed brown spots 1-2” in diameter around cutworm burrows. The Army Cutworm is the most common in Colorado and in the adult life cycle it is known as a Miller Moth. Topical insecticides and granular insecticides are most effectively applied in the afternoon or evening prior to night time feeding. Please note the Army Cutworm is a completely different insect than Armyworms which migrate to Colorado during the summer and rarely cause any damage to the turf as they cannot survive Colorado winters.
White grubs are the larvae of many different beetles, including the Japanese beetle. The grubs live below ground feeding on the roots grass plants and can quickly kill areas of the lawn.
They are most destructive mid-late summer, but the damage they cause may not show up until early fall and by then, it’s too late. Damaged areas of turf may pull up like carpet with white grubs found close to the surface. The grubs are creamy white in color and curl themselves up into a distinctive c-shape. Although preventative systemic insecticide treatments have been shown to control white grubs, Elk Creek does not endorse this treatment option as too many beneficial lawn organisms will also be killed. A granular or liquid insecticide applied when damage first appears is the most effective way to treat this insect. Applications need to be deeply watered into the root zone where grubs are feeding for maximum control.
Billbugs are a type of a weevil and while adults rarely cause significant injury the billbug grub is a very destructive phase of this life cycle. The grubs are white or cream colored with a brown head and are legless. Up to ½” in length once mature, young grubs feed on the crown of the plant and can kill it. Shoots are easily detached at crown level. Older grubs may feed in the lower crown and root region leaving behind a sawdust like substance. Billbug injury is most common on newly seeded or sodded lawns. The best treatment option to control the Billbug is with a topical insecticide during the adult life stage. However, lawn damage does not appear until after the grubs have hatched and feeding has begun so a deeply watered insecticide is the most effective control. The Bluegrass Billbug and Denver Billbug are the most common types for our area.
The Cranberry Girdler is also known as the subterranean webworm. Also the larvae of a moth, they can be identified by a red head atop a white body. Damage symptoms appear similar to white grub infestations as the Cranberry Girdler also feeds on the roots of the plant. Large areas of damage will also pull up like carpet and treatment for this insect is the same, a deeply watered insecticide to reach the root zone. Damages appear in late summer and early fall.