Damage
Distant: Skunk and raccoon activity may be the first sign of a grub problem. The turf will be dug-up and flipped-over during the night. The damaged area will get larger each night. Another symptom of a grub infestation is when turf becomes thin and sometimes dies in patches.
Up close: Dead patches or large areas of thinning, browning or dead turf. The grass can often be pulled back easily because most of the root system has been consumed by grubs.(Images D & E)
Time of year when damage appears: March to October
Host: All grass types
Site: Lawns and most types of non-irrigated turf. June beetle grubs and damage are unusual in irrigated lawns and golf course fairways, tees and greens.
Description of damaging stage: 0.5 to 1.5 inch long C-shaped white grubs. They have 6 legs, a brown head capsule, and visible chewing mouthparts (Image F). Damage will generally only occur when some of them are at least a ¬Ω inch long but there may be a range of sizes of grubs present.
Management
Sampling: Hands and knees - Look at the edges of dead patches to find damaged grass stems and stems filled with frass. Look in the soil around the crown and roots for the larvae.
Managing Billbugs: If damage and larvae are observed, it may be too late to do anything in that calendar year. Avoid any applications of synthetic pyrethroid insecticides such as deltamethrin, cyfluthrin, bifenthrin, permethrin and lambda-cyhalothrin for the rest of the current year and the next year against other insect problems as these will kill natural enemies of billbugs and will contribute to billbug population increases. Apply clothianidin or another neonicotinoid insecticide (such as clothianidin, imidacloprid or thiamethoxam) in late May of the year following the damage.
Preventing Pest Injury to Turfgrass: Home lawns, recreational turf and golf course roughs can be managed to avoid insect injury without insecticides by using proper fertility, mowing at a height of 3.0 to 4.0 inches, and watering during dry periods. This will build a dense stand of turf and a diverse community of insects that will keep turf pests under control. All lawns in Michigan will typically start off lush and green in the spring and will go dormant and turn brown during periods of little rain. Information on the use of insecticides to treat turf pest problems is only meant to be used for the unusual cases where turf damage from pests becomes unacceptable. Even then, insecticides should only be used in areas of a lawn with severe turf damage, and only until a dense turf is re-established.
Using insecticides: Use insecticides judiciously, temporarily, and only in response to unacceptable turf injury. Many insecticides are poisonous if ingested, and therefore must be stored in places where they cannot be found by children. Use the rate recommended on the label for the pest you are attempting to control. Wear rubber gloves, safety glasses (or goggles), rubber boots, long pants and long sleeved shirts when mixing and applying insecticides. The most caution is needed when mixing a concentrated insecticide in water, because skin contact with the concentrated insecticide in the original container is more dangerous than contact with the diluted insecticide after mixing. Water the turf immediately after applying the insecticide to wash it to the base of the plants or into the soil and allow the turf to dry before allowing access by people and pets.
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