Black Turfgrass Ataenius and Aphodius Beetles

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Black turfgrass ataenius adults (left) have a straight hind tibia while the Aphodius species have two "bumps" on the hind tibia.
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Both Ataenius and Aphodius grubs have anal pads that cause the grub to look like they have "bumps" on the tip of the abdomens.
  • Scientific Name: Ataenius spretulus (Haldeman) and Aphodius spp. [usually A. granarius (L.)]. [Phylum Arthropoda: Class Insecta: Order Coleoptera: Family Scarabaeidae]


  • Common Names: Ataenius beetles, Aphodius beetles, black fairway beetle


  • Climatic Zone: Temporate


  • Geographic Distribution:

The black turfgrass ataenius (BTA) has been collected from at least 40 of the 48 contiguous states and probably occurs in all 48. The first record of damage was reported from Minnesota in 1932. The next report of damage was in 1969 on two golf courses in New York and in 1973 in Ohio. Since then, damage has occurred in most of the states where cool-season grasses are grown. Aphodius larvae have been found damaging turfgrass on golf courses, especially in northern (Michigan) and western states (Colorado, Iowa, and California). The small black beetles have the shiny bodies and elongate shape characteristic of BTA but have been identified to be in the genus Aphodius.


  • Damaging Stage: larvae, adults can be a nuisance on golf green surfaces.


  • Hosts:

BTA larvae are known to feed in the root systems of annual bluegrass, bentgrass, and Kentucky bluegrass. While common on golf courses, adults and larvae are often found in home lawns, but damage is rare in lawns. Aphodius larvae are most commonly pests on golf courses where annual bluegrass, bentgrass and Kentucky bluegrass are grown.


  • Damage Symptoms: First symptoms of injury may appear from mid-June to mid-July. Turf shows evidence of wilting. Wilted areas are especially visible when viewed toward the sun. Under continued stress from summer heat and larvae consuming roots, the turfgrass dies in irregular patches. Damage may recur in late August and early September in areas where two generations occur. Populations of 250 to 300 larvae frequently are associated with heavy damage. Turfgrass areas under stress from heat, moisture shortage, or heavy traffic show most severe damage.


  • Description of Stages: BTA and Aphodius larvae look like small typical white grubs but the adults are more elongate (and smaller) than other turf infesting scarabs. BTA has one or three generations per year depending on location. BTA and Aphodius adults and larvae can be identified with a 10x hand lens.

Eggs: The pearly white eggs are approximately 1/64 inch (0.52 to 0.72 mm) long and are laid in clusters of 11 to 12 eggs. The eggs expand slightly when moist.

Larvae: The C�shaped white grubs are very small but third instars can be separated from other grubs using a 10X hand lens. The tip of the BTA abdomen has two distinct anal pads and the few raster bristles are scattered at random. Smaller grubs have these characters but a microscope may be needed to see them. Full grown larvae are approximately 1/4 inch long. Third instar Aphodius grubs can be distinguished from BTA by a short V-shaped raster pattern and a cleft anal pad at the tip of the abdomen. The V is visible with a 10x hand lens, but the cleft pad requires a dissecting microscope to see.

Pupae: The small, 1/4 inch (6 to 8 mm) long pupae are first white but become reddish with maturity.

Adults: BTA adults are small, shiny black beetles, 3/16 inch (3.6 to 5.5 mm) long and 1/8 inch (1.7 to 2.4 mm) wide. The prothorax has small pits scattered over the surface and the wing covers have distinct longitudinal grooves. Newly emerged adults are reddish to dark chestnut brown (tineral) but these become black in a few days. A. granarius (L) is almost the same size as BTA but the head and pronotum are more rounded. The easiest method of distinguishing BTA adults from Aphodius is examination of the hind leg. The hind leg of Aphodius has two bumps or spurs on the tibia (the long segment just before the series of small tarsal segments). Ataenius adults have a smooth tibia.


  • Life Cycle and Habits:

There are many species of Ataenius in the United States and most are dung feeders. A. spretulus and A. strigatus, feed on decaying thatch as well as living plant roots. Optimum habitat for BTA seems to be short cut turf with a moist, compacted thatch layer. BTA adults overwinter in the thatch and underlying soil of turf, under leaves and other debris along the edges of fairways and in adjacent wooded areas. Adults begin to emerge and return to golf courses or other nearby expanses of turfgrass in late March when crocus bloom through when redbuds are in bloom. Migration from overwintering sites continues through April and early May when adults often are seen on greens and swarming in flight over fairways on warm afternoons. Adults alight on the grass surface and immediately burrow into the turf. Egg laying begins in early May when Vanhoutte spirea come into full bloom and continues into mid-June. Eggs are deposited in clusters of 11 to 12 in the soil or thatch just above the soil. Eggs hatch and larvae are present from late May to mid-July in the thatch and soil. While the larvae feed on roots of bentgrass and Kentucky bluegrass, damage is most common on irrigated fairways with a high percentage of annual bluegrass. Symptoms of injury at this time include wilting of turf in spite of regular irrigation. In late June and July, mature larvae burrow one to three inches into the soil, pupate, and become adults that emerge in July and early August. The reddish and black adults are often numerous beneath turfgrass killed by larvae. Black adults are seen around lights at night. Where two generations occur, first generation adults begin egg laying when Rose of Sharon comes into bloom, in July and produce a second generation of larvae. Second generation larvae can cause the same symptoms and significant injury as the first generation. In Minnesota and other more northerly states, the second generation of BTA apparently does not occur. In Ohio, completion of larval development and pupation of the second generation occurs in late August and September. These adults emerge and leave the fairways for overwintering sites during September and October. Larvae that do not complete development to adults do not survive the winter. Aphodius appears to have only one generation per year and the larval damage often occurs a bit later than normal, first generation, Ataenius damage.


  • Control Approaches:

Cultural Control - Manage Thatch - Generally, BTA and Aphodius infest moist thatchy turf grown on soils high in organic matter. Management practices that help reduce thatch and compaction may help to reduce the chance of attracting adult beetles and building up damaging infestations.

Natural Control - Milky Disease - A milky disease specific to BTA larvae is a major factor in natural suppression. A similar bacterial disease infests Aphodius. Neither of these insects are affected by the milky disease that infects Japanese beetle grubs. Disease levels as high as 70% of the larval population may occur, effectively controlling the pest. In areas with two generations of BTA, infection levels are highest in the second generation. Infected grubs are often noticed after application of fast acting, short residual insecticides. Apparently, the insecticide kills healthy, feeding grubs because a consequence of the infection is that the grubs stop feeding. The presence of these living, but diseased grubs may lead to the false conclusion that the insecticide treatment was ineffective. Surviving larvae should be examined carefully for milky disease – they will appear to be a solid milky-white color with no dark areas in the abdomen (from gut contents). The more infected grubs seen, the better since the dying grubs deposit millions of bacterial spores that will suppress future infestations.

Biological Control – Insect Parasitic Nematodes - Two insect parasitic nematodes, Steinernema glaseri and Heterordabditus bacteriophora are labeled for curative control of BTA larvae. Control with H. bacteriophora has been good but variable with S. glaseri. Though these nematodes are not labeled for control of Aphodius, H. bacteriophora may provide control.

Chemical Control - Insecticides -

Curative treatments. When observation determines that treatment should be applied, products known to have rapid action and are least affected by binding to thatch are effective. Irrigation immediately after application (before spray applications dry) is key to achieving maximum control. Remember, survivors of such applications are often infected with milky disease.

Preventive treatments. The recent labeling of long residual (100+ days) neonicotinoids and diacylhydrazine insecticides has made it possible to achieve “annual” grub control with a single application in May, June, July, or August. Application during the first week of May also provides control of Aphodius as well as first and second generation BTA. Application of some of these new insecticides at this time also provides control of a broad range of insect pests other than grubs. These new materials have low impact on beneficial organisms that live in turf. Both liquid and granular formulations are available. Some require post-treatment irrigation, others do not. Read and follow label instructions for optimum results. Where BTA is a perennial problem, applications of residual action insecticides in late April or early May have been effective in killing ovipositing adults, thus eliminating any larval infestation. The best time to apply this treatment is when Vanhoutte spirea (Bridal Wreath spirea can be substituted) is in full bloom.

Monitoring

Adult BTA can be numerous on greens in May and June. In fact, adults can be found on close mowed turf throughout the summer. The presence of these adults does not necessarily mean a damaging population of larvae can be expected. Fairways, tees, and all putting surfaces should be observed daily from mid-June through, at least, mid-July for evidence of wilt that precedes damage from BTA. If two generations normally occur, observations should continue in August and September. In areas where Aphodius occurs, observation should begin in early June. A golf course cup cutter is an effective tool for examining locations showing wilt or slight yellowing. Grubs are usually found at the thatch-soil interface; however, smaller larvae may be in the upper thatch. Early symptoms of BTA or Aphodius infestations are often misdiagnosed as disease or localized dry spots. Only by examination of the thatch and soil under such turf can the true cause of these symptoms be determined. Misdiagnosis can be a costly mistake.

Thresholds

Various thresholds of larval infestations have been proposed for BTA, the most common being 50 per ft2. The level of fertility, irrigation and overall turf health determines the level of infestation that can be tolerated. “Healthy” turf can tolerate much higher levels that 50 per ft2. Further, infestation history, budget, course standards and philosophy of the superintendent are major factors in deciding whether curative, preventive or no control measures are warranted.