1. Turf grass Pest Management, Category 3A Chapter 9, Insect and Vertebrate Pests
  2. In Michigan, two groups of animals commonly injure turfgrass. These include insets and vertebrates. Insects actually eat or ingest parts of the turfgrass plant, and vertebrates typically tear up the turf looking for food but don’t usually consume the turf.
  3. As with any pest problem, the firs step in managing turfgrass insects is correct identification. There are hundreds of insects found living in turfgrass, but only a few cause problems. To be certain of what is injuring your turf, it is necessary to recognize pest-insects in all of their life stages. Knowing their life stages and their feeding habits will assist your identification activities.
  4. When identifying turfgrass insects, it is helpful to group them according to how they damage the turf:
  1. Several beetle larvae are called white grubs. The C-shaped white grub is the immature stage of the beetle pests in the Scarabaeidae family.
  2. You may be familiar with the Japanese beetle since it is a landscape pest in both the adult and the immature stages. Turf damage occurs when the white grubs, that have overwintered in this life stage, feed on the roots in May and early June. These grubs pupate into the current season’s adult beetles.

    3. These beetles lay eggs for the current season’s generation of white grubs that feed on the turf roots in September and October before going deeper into the soil to overwinter. The C-shaped white grubs hatch 1/16" long and can reach up to 1" in length when mature.

    Grub feeding eliminates portions of the root system. When damaged turf experiences water stress the remaining roots are not sufficient to replenish the water needs of the plant and the turf turns brown and may die.

    Unirrigated turf will likely show injury when 10 or more grabs are found per square feet. When populations reach 20 or more per square foot, injury is likely even on irrigated turf.

  3. Japanese beetle adults are stout-bodied, dark green metallic, and copper-colored with tufts of white hairs along their sides. They emerge in July and early August and feed on the foliage and flowers of fruit trees, roses, basswood and wild grapes among other plants. They lay their eggs in the turf also during late July and August.
  4. Eggs hatch into the C-shaped grubs in August and begin feeding on turf roots. When more than 10 grubs per square are feeding, brown patches turf may result. If the turf is moisture stressed the damage is more significant. In late fall, the grubs move deeper into the soil and overwinter there. After feeding the next spring, the grubs pupate in June.
  5. Determine grub populations by sampling in late August or September. Skunk and other vertebrate activity are indicators of grub populations. When grubs are present, be sure to keep the turf well irrigated. This will prevent some turf loss by providing adequate moisture. If insecticides are warranted, follow all label directions and water the product in so that it reaches the turf root zone.
  6. When treating for Japanese beetles, the results are likely to be variable between sites. Three weeks after treating, sample from the original grub locations and record your results.

    7. There are adult beetle traps on the market. These are ineffective in controlling this pest. The biological insecticides are also variable in their efficacy. If you use these products, return to the sites and check the level of control obtained.

  7. European chafer is another beetle with C-shaped grubs that feed in the spring and fall. These grubs can also grow to be 1" long when mature. Irrigated turfgrass will suffer damage when grub populations reach 20-30/square foot. This is when insecticide treatments should be considered.
  8. The adult European chafer is a light brown, stout-bodied beetle with clubbed antennae. The adults emerge in late June and July. European chafers have a similar life cycle to Japanese beetles. That is –the adults emerge in summer, they lay their eggs in July and August. The eggs hatch into grubs that feed on turfgrass roots. The grubs then move deeper into the soil and overwinter. The following spring the grubs feed again before pupating.
  9. European chafers may be considered a more serious turfgrass pest because they feed longer in the fall and return to the surface and feed earlier in the spring than the Japanese beetle.

    10. Action thresholds, control tactics and timing are similar to those for Japanese beetle --- 10 grubs/sq. ft on unirrigated turf, and 20-30sq. ft on irrigated sites.

  10. June beetle larvae are another C-shaped grub. These larvae feed all summer, from May through October. As turf roots are consumed, the grass turns brown and may die from moisture stress. These grubs grow up to 2" long! Since they are larger, feed all season and consume more roots, the threshold for these grubs is lower than the threshold for Japanese beetle or European chafer. Turf injury is likely when June beetle populations reach 5/square foot on unirrigated turf and 10/square foot on daily-irrigated sites.
  11. There are several species of June beetles in Michigan. Some people refer to them as May beetles. Although the adults are active only for about two weeks, people notice them because they are attracted to lights and are very active between 7 and 9 p.m. During the two weeks of adult activity, they feed on tree leaves, mate and deposit eggs in grassy soil. These beetles have a 3 –year life cycle.

    12. When the eggs hatch, the small larvae feed on turf roots and organic matter until September. They move deep into the soil to overwinter. The second year is when the most turf damage occurs since the grubs feed briefly during spring and early summer. NOTE: The larger the grubs are, the more difficult it is to control them. In late summer, June beetle grubs pupate and the adult beetles emerge in fall. The adults overwinter in the soil until the next May or June, thus completing the 3-year life cycle.

  12. The most serious injury associated with June beetles is usually the damage that occurs when skinks turn over the grass to feed on the grubs. There are several natural enemies that typically keep June beetles populations in check. If chemical control is warranted be sure to time the application when the grubs are susceptible. First or second-year grubs are the most logical targets for controlling this pest.
  13. Black turfgrass Ataenius is becoming a more common pest on Michigan golf course turf. Their injurious feeding occurs form about mid-July into August. The larvae are small C-shaped grubs. The adult are shiny black, tablet-shaped beetles about ¼" long. Since they are small, turf can tolerate approximately 60 to 100 grubs/square foot before injury is obvious.
  14. Ataenius overwinter as adults and begin flying about in May. Eggs are laid in June. The small grubs hatch and feed through August. Turf injury is significant where large populations are present or when turf suffers moisture stress.
  15. On sunny days during the spring and summer, Ataenius adults can be found crawling around on golf course greens. While a majority of the adult activity occurs in the spring, it is not uncommon for adults to be found sporadically all season-long.

    16. The best time to sample for Ateanius grubs is during July. Irrigated turf, that is not otherwise stressed, may tolerate up to 100 grubs/square foot before injury becomes significant. For high valued turf, treatments may be warranted when population density reaches 60+ grubs per square foot. This is the last of the C-shaped grubs we will discuss.

  16. Hairy chinch bugs cause damage to turf in July and August that resembles drought injury. Chinch bugs are black with white wing markings and are 3/16" long. The larvae are smaller versions of the adults without wings and red in color. Monitoring for these insects requires getting on your hands and knees and parting the grass, looking for their movement and damage. Using the flooded coffee technique as described in chapter one, also works for detecting this pest. Thresholds for this insect include 20 bugs found during two minutes for monitoring or when 15 bugs are found while flooding a coffee can.
  17. There are two generations of chinch bugs per year in Michigan if your locations south in Lansing. In areas of Michigan north of Lansing, only one generation occurs. Chinch bugs overwinter adults emerge in May, and the second generation of adults are present in July and August.

    18. Adults chinch bugs lay eggs in the leaf sheaths of grass plants. Both the larvae and adults suck out sap. Their saliva contains substances toxic to the plant and puncture wounds often block water movement.

  18. Chinch bug injury can be serious when warm, dry conditions induce water stress in grass plants. The damage is a characterized by irregularly shaped yellow patches 2 to 3 feet in diameter. The patches often turn brown and die. Some weeds may survive in these areas. The injury looks like drought or heat stress, but is not eliminated by applying water.
  19. Heavy rainfall in June and early July during egg hatch will reduce larvae survival. This is due to a naturally-occurring fungus that attacks the bugs specifically during cool, wet conditions. Although chinch bugs are widespread, populations are rarely large enough to cause significant damage. If well-irrigated, lawns can tolerate low-level chinch bug populations.
  20. Bluegrass billbugs damage the turf while in their immature stage. Immature billbugs are small, white, legless grubs. Turf thresholds will vary site to site, but if small areas of the lawn are damaged it can be expected to recover with proper water fertility.
  21. The billbug life cycle begins with the adult weevil overwintering in the soil. Adults become active when temperatures warm up in the spring. Most eggs are laid in grass tems in early June. Egg hatch follows in one to two weeks. The larvae tunnel down through the grass stems and into the crown or around the roots. Mature larvae often feed across the plant crown cutting off the root system, and then pupate in the soil. There is one generation per year with the density of larvae peaking in July. These larvae pupate and the adults emerge in late August or early September. These adults soon locate protected areas to spend the winter.
  22. Bluegrass billbugs are most commonly found attacking Kentucky bluegrass but can sometimes be found in fescue and perennial ryegrass. Damage is evident in late July and is characterized by irregularly-shaped dead parches of turf scattered throughout the lawn.

To diagnose blue grass billbug injury, look for the following signs:

Record areas that suffered excessive billbug injury, so that these areas can be closely monitored and treated if necessary, next May.
  1. Black cutworms are more problematic on golf course greens than other higher cut turf. They create ¼" holes with closely-clipped grass plants around the entrance. The cutworms are dark-brown caterpillars that grow from ¼" to 2" long. The threshold depends on the type of turf being managed.
  2. Cutworm adults are dull-colored moths that may be attracted to lights. The moths appear in late spring and the cutworms are usually first found in early July. Cutworm activity usually peaks in July and again in August. There may be two or more generations per season. Cutworm activity is characterized by clipped grass and green fecal pellets associated with their feeding.
  3. As mentioned, this feed activity is most problematic on golf course greens where the mowing heights allow the injury to easily be revealed. Higher cut turfs such as home lawns and fairways mask the injury and furthermore have more predators available for keeping the cutworms in check. Disclosing solutions, as discussed in chapter1, can be used to detect cutworm presence.
  4. Sob webworms cause small brown patches of turf where they have clipped off grass blades at the base. When these patches merge together, larger irregular patches of dead turf are formed. The immature stage causes the damage. Sod webworm larvae are ivory white caterpillers with small black spots. Larvae grow from ¼" at egg hatch to 1" long. The tolerance of sod webworms depends on the importance and use of the turf.
  5. Sod webworm caterpillars overwinter in the soil and resume feeding in the spring as temperatures begin to rise. Occasionally, damage will occur in the spring from large numbers of overwintered webworms.

    6. There are two generations of sod webworms per year. The dirty white adult moths emerge in late May and June, and can be seen flying across lawns at dusk. As females fly over the grass, up to 200 eggs per moth may be dropped into the grass. Eggs hatch in 5 to 10 days and the young larvae begin eating the grass, up to 10 days and the young larvae begin eating the grass blades. After feeding these larvae pupate in late June and early July. Second generation adults are seen shortly afterward. These adults soon lay eggs and the second generation larvae reach peak activity in mid to late August.

  6. It is the second generation that is the most damaging. Most turfgrass is susceptible to webworms, but bluegrass and bentgrass lawns appear to be favored.

Sob webworm diagnosis may be aided with these clues:
  1. Larvae in the lawn can be brought to the surface by drenching the infested area with a disclosing solution as discussed in chapter one. If more than 4 to 6 larvae are found per 4 square feet of lawn, treatment may be warranted. Sod webworms have many natural enemies. It is when these natural enemies are suppressed by pesticide use that webworms are likely to become a problem.
  2. Ants are a pest to turf not because they feed on the grass, but because of their mound-building activities. Ants are red, black, or brown. Size and color depends on the species. The number of ants considered unacceptable depends on the type of turf being managed and it intended use.
  3. For the most part, ants are beneficial. They consume a broad range of other insect eggs and larvae. They are often responsible for keeping populations of turf pests under threshold numbers. Again, ants do not damage the turfgrass plants directly. It is their activity that ruins surface uniformity that is objectionable. Golf greens and sandy soils suffer the greatest damage. Insecticide treatments provide only short-term suppression and may injure non-target insects.
  4. Insect management begins with maintaining a vigorous, dense stand of turf. Turfgrass that is adequately watered and fertilized can tolerate more insect-feeding than turf under stress. Further, healthy turf can recover from insect injury much more readily than ill-maintained, insect-injured turf.
  5. Healthy turf is best grown without insecticides. Insecticides destroy both insect pests and beneficial insects. Insecticide use also limits organisms important for thatch decomposition, such as earthworms.
  6. If an insect pest is causing unacceptable injury that cannot be adequately managed through non-chemical methods, then the infested areas of turfgrass may warrant an insecticide treatment.
  7. Remember that proper use of insecticides requires you to:
    1. Monitor the turf frequently. Apply insecticides only when and where needed.
    2. Protect beneficial insects and mites. Spot treat when possible and aim to lower pest levels to acceptable levels rather than trying to eradicate the organism.
    3. Carefully time insecticide applications to coincide with the pest’s susceptible life stage. Monitor the turfgrass regularly to observe pest activity and development.
  1. Proper use of insecticides also requires you to:
    1. Avoid preventive treatments except when intolerable damage is certain to occur.
    2. Use the lowest toxicity insecticide available that will get the job done. Avoid broad-spectrum insecticides. These choices will limit the effect on non-target organisms.
    3. Record and evaluate the results of your insecticide application.
  1. Vertebrates are animals with backbones. They are large in comparison to insects. Vertebrates that eat turf pest could be considered beneficial, except that they tends to injure turf in the process.
  2. Birds are vertebrates and cause injury by puncturing pencil-thick holes in the turf as they forage for grubs and caterpillars. Some of them use their feet to rake away the turf to expose their prey. The blackbird family including starlings, redwing blackbirds, and grackles cause the most injury to turf.
  3. Skunks, opossums, and raccoons will tear up turf looking for grubs and other organisms living in the soil. Their activity is often the first sign of a grub infestation.
  4. Moles live in underground burrows and have greatly enlarged front feet for tunneling through the soil. Moles lack external ears and have very tiny eyes. As they travel through the soil, they create up-heaved ridges. The ridges make mowing difficult and ruins the surface uniformity.
  5. When managing vertebrate pests of turf, consider the entire picture. Begin by removing their food source, if at all possible. Use barriers and repellants if the site lends itself to protection from these products.

    6. Trapping is an effective way to remove established vertebrate pests. Trapping requires a fair amount of labor and knowledge about the pests habits to be effective. Before trapping, you must obtain a Wildlife Damage Investigation and control Permit form your district office the Department of Natural Resources. Permits are not required for mice (voles), rats,, moles, or chipmunks.

  6. There are relatively few pesticides marketed to control vertebrates because they are hazardous to desirable wildlife, pets, and humans. Use poisonous products only when alternative measures fail to limit vertebrate damage to an acceptable level. Be especially cautious to place baits in a manner and during a time that avoids or limits exposure to nontarget organisms.

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  7. This concludes the review session for category 3A, turfgrass pest management. Good luck in preparing for your certification exams. Have a good season.