Lawn Insects

 White grubs are a very common pest of turfgrass, causing damage to lawns .  White grubs are the larvae of several different species of scarab beetles. June beetles, Japanese beetles, European chafers and Asiatic garden beetles.  June beetles have a three-year life cycle. Adult June beetles lay eggs in the soil in the spring. After eggs hatch in three to four weeks, the larvae will proceed to feed on roots of plants present in the soil. As temperatures cool, the grubs will burrow deeper into the soil to overwinter. As temperatures warm in the spring, grubs return to shallower zones in the soil to feed for another growing season. Grubs will overwinter again, but in the following spring they will enter the pupal stage and remain in the soil for the rest of the year. Adults emerge from the soil the following spring, mate and will return to the soil to lay eggs, completing their life cycle.  If you suspect a grub problem in your lawn, dig up a few squares of turf, including the top 2 to 3 inches of soil under them, around the edges of the damaged areas and look for c-shaped white grubs. If grubs caused visible damage to your lawn, you won’t have any trouble finding them.

 Cranflies generally have a single generation per year. The adults, which resemble giant mosquitos, begin to fly in August. The two species are difficult to distinguish from each other.  The European cranefly deposits eggs in the soil in August or September. Young leatherjackets begin feeding on turf roots in September. They overwinter in the soil and resume feeding in April and May. Larger larvae come to the surface at night and feed on grass blades and crowns, sometimes causing a scalping effect in small patches. Larvae complete development in early June, moving about 3 inches deep into the soil to pupate. European cranefly adults do not emerge until August, but common cranefly may have two generations per year with adults emerging in the spring and the fall.   Damage appears in the spring after the turfgrass begins to green. Infested turf may be thin and brown or closely cropped in patches. Small patches may coalesce into large patches of bare soil or dead turf.  Up close, patches of scalped or dead turfgrass is visible with leatherjacket larvae in thatch or top layer of soil.  The larvae (called leatherjackets) are grayish-brownish, and look like a thin caterpillar with no legs and no visible head. Most of the damage is caused when they are full grown in the spring.   Craneflies prefer turf growing in moist soils with high organic matter 

 Most of the damage happens in July and August when chinch bugs are full-grown. Plants are injured by a small amount of chinch bug saliva that enters stems when they are sucking juices out of grass plants. This causes patches of infested turf to slowly turn brown and what may begin as a small patch of dead grass will quickly grow into a large area of dead grass, constantly expanding outward.  The adult stage and large larvae cause the most damage. Adults are 1/8 inch long and have piecing/sucking mouthparts, like a needle. Large larvae are almost entirely black, but adults have wings with angular white markings. Young larvae are smaller and red. Damage typically occurs in the sunniest areas of your lawn, especially when the weather is hot or dry. Thick, lush lawns are especially prone to chinch bug damage as the thick thatch offers a great place for adult chinch bugs to feed and lay eggs.

 Webworm larvae are 1/4 to 1/2 inch long, ivory-colored caterpillars with dark brown or black spots.  More than one species is found in Michigan, but the bluegrass webworm has two generations per year with larvae present in late June to July and again in September. They are difficult to find because they hide in silken tunnels in the thatch during the day. Webworm larvae have a brown head capsule, 6 short thoracic legs, and the last few abdominal segments narrow at the tail end.  Adult female moths can lay up to 200 eggs, and the eggs are laid randomly around your yard. This makes it tough for inspection and treatment because there will be no area more likely or less likely to have a sod webworm population when these insects are present.   After eggs hatch in late spring, the webworms will begin to feed on the grass. This type of lawn pest is always above ground, and they feed on grass blades.

• When the worms are small, the grass blades are skeletonized, which means the soft leaf tissue is eaten while the veins of the leaf remain.
• As they continue to get larger, the worms will start to eat whole pieces of the blade, and grass will appear notched.
• Eventually, whole blades will be clipped off at the crown. The worms take the blades into their silken tubes to eat them.
• Since the worms cut the grass off at the crown, brown patches will form. At first, they'll be small, but eventually they grow and combine to form even larger patches.

This type of damage can go unnoticed during drought conditions, and also may be confused with dog damage. A good indication of sod webworm damage is that the grass has been clipped, and is not simply dead grass.

Billbugs are small beetles that feed on and lay eggs in turf grass. Billbug larvae cause the most damage to turf as they feed on the grass blades and eventually the roots.  Billbug larvae cause the most damage, making correctly identifying them very important. Larvae are white and legless, with darker heads. They are fairly small, and full grown larvae will only be about 1/2 inch long. You will find these larvae in the crown of your turf as well as below the thatch layer, not necessarily in the soil. White grubs and billbug larvae can often get confused for each other. Remember, white grubs are c-shaped, creamy white, with dark heads and defined legs. They can be up to an inch long when full grown and live in the soil feeding on roots of the grass. Billbug larvae are legless and not c-shaped.   

Description of damaging stage: Small, legless, white larvae with a brown head capsule. They can be less than inch long when full grown. The larvae will start feeding inside the stems. When they become larger, they will move out of the stems and feed on the roots and crowns of the grass. When there are enough present to cause damage, they leave a fairly obvious amount of sawdust-like excrement (called frass) where they are feeding.