TURFGRASS PESTS IN THE NORTHEASTERN USA

Dr. Albrecht M. Koppenhöfer, Specialist in Turfgrass Entomology, Ph: (732) 932-9802

Turfgrasses cover > 30 million acres in the USA, more than the combined area of the New England states. Most of this area is subdivided into ~50 million lawns; the remainder is in golf courses, parks, athletic fields, cemeteries, sod farms, etc. A typical U.S. community of 100,000 citizens has 3,800 acres of turf areas requiring 100 professionals and $8 million to maintain. Turfgrass culture, in its many forms, is a $45 billion per year industry in the USA. Turfgrass provides substantial environmental, recreational, and aesthetic benefits including: 1. control of water and wind erosion, 2. capture and cleaning of runoff water from urban areas, 3. soil improvement and restoration, 4. moderation of temperatures, 5. improvement of air quality, 6. noise and glare reduction, 7. reduction of pest, pollen, disease exposure, 8. wildlife habitat, 9. improvement of physical and mental health of urban population.

I. Root-infesting insect pests

Insect that live in the soil and feed upon roots and rhizomes are among the most devastating turfgrass pests. The major pests in this group include a complex of white grub species on cool- season grasses and mole crickets on warm-season grasses in the south. Soil-dwelling pests are difficult to control because surface-applied insecticides have to penetrate through the turf canopy and thatch layer to reach the target zone. a. WHITE GRUB COMPLEX (Coleoptera: Scarabaeidae)

Pest status. White grubs are the most widespread and destructive insect pests in the cool-season and transition zones.

Injury. The grubs chew off the roots close to the soil surface. In hot, dry weather this can lead to quick loss of turf. Early turf symptoms include gradual thinning, yellowing, wilting in spite of adequate soil moisture, and appearance of scattered, irregular dead patches. The patches increase in size and join. Infested turf feels spongy underfoot and can be pulled up or rolled back easily, exposing the C-shaped white grubs. Additional, and often more severe, damage can be caused by vertebrate predators (birds, skunks, raccoons, moles) digging up the turf to feed on the grubs. Presence of these predators is often a good indication for grub infestation. The adult beetles do not cause damage to turfgrass but may be major pests of woody and herbaceous ornamentals.

Plants attacked. All cool-season and many warm-season grasses are susceptible to white grubs.

Distribution. At least 10 species are pests of turfgrasses in North America including native (masked chafers, black turfgrass ataenius, May beetles, green June beetle) and introduced species (Japanese beetle, Oriental beetle, European chafer, Asiatic garden beetle). Distinguishing characteristics. The adults are stout, oval beetles. The tibiae of the front legs have stout teeth on the outer margin that help the beetle to burrow in soil. The last 3 antennal segments are flattened and held together to form a club. Males have larger antennal clubs. The eggs are shiny, milky white, and oval, becoming swollen and more spherical as they absorb water from the environment. The body of the grubs consists of a distinct brown head capsule with chewing mandibles, a thorax with 3 pairs of short, jointed legs, and a 10-segmented abdomen. Thorax and abdomen are whitish or cream colored, but the hind part of the abdomen often appears dark because of ingested soil and food in the gut. When feeding or resting the grub assume a typical C-shaped posture.

Identification of grub species. Adults of different species differ in size, coloration, and habits. Within the groups of masked chafers and May beetles, differentiation is difficult. The grubs can distinguished by examining the raster (arrangement of spines and hair) and the shape of the anal slit on the underside of the last abdominal segment.

Live history and habits. The life stages consist of egg, 3 larval instars, pupa, and adult. Asiatic garden beetle, oriental beetle, Japanese beetle, and masked chafers have a 1-year life cycle. Adults emerge, mate, and lay eggs in mid-summer. The eggs are laid in the soil at 1-5” depth and hatch in 2-3 weeks. The grubs grow quickly, molting twice, and by fall most of them are nearly full-sized 3rd instars. Declining soil temperatures in late fall force the grubs to move deeper in the soil where they overwinter. In spring they resume feeding for about 1 month. For pupation they move deeper in the soil. Adults emerge several weeks later. The damage of the annual white grubs shows up in late summer and early fall (August/September) when the voraciously feeding 2nd and 3rd instars coincides with heat and moisture stress in the turf. Damage during the spring feeding period is less apparent because environmental conditions allow the grass to outgrow the loss of roots. Because of their different life cycles, the black turfgrass ataenius (usually > 1 generation per year) and May beetles (1-4 years per generation) may also cause damage in June or July

Management. Monitoring and sampling are keys to early diagnosis of grub problems. Sites with heavy beetle activity in June/July are more likely to have grubs in summer. Watch for swarms of adults beetles skimming over the grass at dusk (masked chafers), green June beetles buzz-bombing, or large numbers of tiny black turfgrass ataenius adults crawling on putting greens or flying in late afternoon. Adults flight can be monitor using light traps for night flying scarabs, or scent traps for Japanese beetle. Be suspicious if moles, skunks, or flocks of birds find the turf attractive. Sample to confirm grub presence as the predators may also be after earthworms or other soil . Mapping and record-keeping are helpful in tracking high-risk areas because the same sites are often reinfested in following years.

Early detection and proper timing are especially important when applying short-residual insecticides for curative treatments because most control agents work best against young insects. Concentrate on probable hot-spots. If long-residual insecticides (e.g. imidacloprid, halofenozide) are used for preventative treatment, targeting those site where heavy beetle activity was observed is less wasteful and more environmentally sound than going “wall-to- wall”. It is rarely necessary to treat an entire lawn or fairway. Threshold density for causing visible damage varies with grub and grass species, and with the overall vigor and use of the turf.

Cultural control. Watering during peak beetle activity in mid-summer tends to attract egg- laying females and increases egg survival. Once the eggs have hatched, however, irrigation increase the tolerance of the turf to root feeding. Effects of light to moderate grub infestations can often be masked by irrigation to alleviate stress, together with light fertilization to enhance recovery. Avoiding plants that attract the adults (food or shelter) along the turf areas reduces the reservoir of egg-laying adults. No resistant cultivars are known. Tall fescue is generally more tolerant of grub damage.

Biological control. Naturally occurring predators, parasites, and pathogens are important in suppressing white grub populations and buffering outbreaks. They should be conserved whenever possible (e.g., spot-treating, avoiding broad-spectrum insecticides). The entomopathogenic nematode Heterorhabditis bacteriophora can be very effective in grub suppression. Milky disease [Paenibacillus (formerly Bacillus) popilliae] occurs in many different strains. Only the strain that infects the Japanese beetle is commercially available. It can currently only be used for long-term inoculative control.

Chemical control. To enhance insecticide penetration, mow the turf and rake out the dead grass and thatch before treatment. Irrigation before application tends to bring the grubs closer to the surface increasing efficacy. Immediately after treatment, irrigate with ½ to 1” of water to wash the insecticide into the soil. Granular formulations are more forgiving if post-treatment irrigation is delayed. Control may be enhanced by returning the grass clippings to the turf for 1 or 2 mowings after application. If the thatch layer is thicker than ½” consider dethatching before application. Curative controls work best when the grub a small (optimum time various with region and grub species). The optimal time for preventative treatments (imidacloprid, halofenozide) is June/July.

5. JAPANESE BEETLE, Popillia japonica

Pest status. Considered the primary insect pest in turf in much of New England and the Middle Atlantic states. Adults are serious pests of ornamental and woody landscape plants.

Plants attacked. Grubs feed on all cool-season grasses, many lawn weeds, and other plants. Adults feed on >300 ornamental and woody landscape plants.

Distribution. Established east of the Mississippi river except FL, MS, and MN.

Distinguishing characteristics. Adult beetles (5/16 to 7/16” long) have a shiny metallic green head and body, with darker green legs. The coppery-brown elytra do not quite reach the tip of the abdomen. The side of the abdomen has tufts of white hair. The rastral pattern of the grubs includes 2 rows of short spines arranged in a V-shape. The anal slit is transverse. Live history and habits. In the Middle Atlantic States, the adults begin to emerge in early to mid-June (peak: early July). They are active during the day and quite conspicuous.

Management. As other white grubs. In addition, egg-laying in adjacent lawn areas can be reduced by avoiding plants attractive to the adults (e.g. lindens, purple leaf plum, bracken, elder, grape, Indian mallow, mulitflora rose, sassafras, smartweed, Virginia creeper). Trapping with pheromone traps is useful for monitoring but does not reduce adult populations.

2. ORIENTAL BEETLE, Exomala orientalis

Pest status. The oriental beetle is a pest of regional importance in the northeastern USA. In recent years it has become more abundant than the Japanese beetle in many areas. The grubs seem to prefer well-kept, open, sunny lawn with rich sandy loam and high moisture.

Plants attacked. Grubs feed on all cool-season grasses, strawberry beds, nursery stock and potted plants. The adults feed on various ornamental plants but are no serious pests.

Distribution. CT, NY, MA, MD, NJ, NC, OH, PA, RI, VA, HI.

Distinguishing characteristics. Adult beetles (3/8” long) are mostly straw-colored, with variable black marking on the thorax and elytra and a solid dark brown head. The larval raster consists of 2 parallel rows of short, stout inward-pointing spines. The anal slit is transverse.

Live history and habits. Adults are active from late June to August (peak: mid-July). Adults are mostly active around dawn.

Management. As other white grubs.

3. EUROPEAN CHAFER, Rhizotrogus majalis

Pest status. May be most serious WG pest of home and low-maintenance lawns.

Plants attacked. The grubs feed on all cool-season grasses in turf and pastures, weeds, and field, forage, nursery crops.

Distribution. CT, DE, NY, NJ, PA, ME, RI, OH, MI.

Distinguishing characteristics. Adults are light reddish-brown (9/16” long) with a slightly darker head and pronotum. Fully mature grubs are just under 1” in length. The raster has 2 distinct, nearly parallel rows of small spines that diverge outward at the tip of the abdomen. The anal slit is Y-shaped. Live history and habits. The adults emerge in early June to mid July (peak: mid June to early July). They are nocturnal and active above 66°F. The grubs stop feeding later in fall and resume earlier in spring than other white grub species.

Management. As other white grubs. Damage threshold is 5-10 grubs per ft2. The grubs are less susceptible to many insecticides (including halofenozide) than Japanese beetle grubs. Adults begin to fly at 1st bloom of hybrid tea and floribunda roses with peak flight at full bloom of common catalpa (Catalpa bignonioides).

II. Pests that burrow in stems or damage crowns

Larvae of several types billbugs, weevils, and flies burrow in the stems and feed on the crowns of grasses. Because it contains the growing points from which roots, lateral shoots, and leaves arise, the growing point is the most vulnerable part of the grass plant. These pests are protected form conventional insecticides during the part of their life when they are feeding inside the plants. Successful control requires knowledge of life cycles for proper timing, or long-residual insecticides with systemic activity.

BILLBUGS, Sphenophorus spp. (Coleoptera: Curculionidae)

Pest status. Several species of billbugs are major pests of turfgrass in the USA. Billbugs damage is often confused with drought stress, diseases or injury from greenbugs or white grubs.

Injury. Adult billbugs chew holes in grass stems. Young larvae tunnel in the stem and then burrow down to feed on the crown. Older larvae feed externally on the crown as well as roots and rhizomes. Symptoms of infestations start with scattered dead stems followed by growing patches of dead turf (see “tug test” below). Billbug damage usually shows up in late summer, especially during extended dry periods.

Distribution and plants attacked. 2 species of billbugs are widespread, important turfgrass pest in the USA. The bluegrass billbug, Sphenophorus parvulus, is most common in the cool- season zone across the continent preferring cool-season grasses, especially Kentucky bluegrass and ryegrass. The hunting billbug, S. venatus vestitus, is most common in transition and southern turf areas where it damages warm-season grasses, especially bermudagrass and zoysiagrass. Other billbug species (e.g. Denver billbug, Phoenician billbug) are more restricted in their distribution. At least in New Jersey several billbug species besides the bluegrass billbug attack cool-season grasses (i.e., hunting, little, and uneven billbug).

Distinguishing characteristics. Adults billbugs are hard-bodied and usually grayish or black. Most species are 5/16 to 7/16” long. The snout, head, and thorax are about as long as the wing covers, and the elbowed antennae are attached near the base of the snout. The snout is long and beak-like. The larvae are legless, cream colored with a brown head, the body somewhat curved, fat through the middle and pointed at the tail. Mature larvae are about 3/8” long. Identification of billbug species. Adult billbugs can be separated using the pattern of pits and furrows on the back. Bluegrass billbugs have small evenly spaced punctures on the pronotum and coarsely striated wing covers with rows of regularly spaced single punctures. Hunting billbugs have a raised Y-shaped area on the pronotum, with a parenthesis-like cuvred line on either side.

Live history and habits. Bluegrass billbug and hunting billbug (in the northern part of its range) have 1 generation per year and overwinter as adults in thatch, soil crevices, or other sheltered locations. The adults become active in late April to mid-May when soil temperatures reach about 65°F and can be seen crawling over exposed areas in search of suitable grass for food. Eggs are laid usually singly in grass stem just above the crown. Most egg-laying is completed by early July but may continue into August. Young larvae tunnel in the stem and then burrow down to feed on the crown. Older larvae feed externally on the crown as well as roots and rhizomes. Larvae are abundant in the soil from early July to early August. New adults are abundant in late summer and fall before returning to their overwintering sites. In the southern range of its distribution, the hunting billbug may have several overlapping generations per year and overwinters mostly in the larval stage.

Management. Monitoring of adults activity can be done by direct observation or placing pitfall traps in out-of-the-way spots and checking regularly. For the bluegrass billbug, a degree-days model has been developed to predict its development. Early detection is difficult because the young larvae reside inside the plants. Once scattered patches of dead grass show up, billbug presence can be confirmed with the “tug test”: Grasp affected stems and pull upward. If the damage is caused by billbugs, the stems should break off at the crown and are hollowed out or filled with sawdust-like frass.

Perennial ryegrass cultivars with fungal endophytes are generally resistant to billbugs. Endophyte-enhanced fescues may also be somewhat resistant. Low to moderate billbug damage can often be masked by light fertilization and deep watering in summer to reduce plant stress. A naturally occurring fungus, Beauveria bassiana, can help suppressing populations in rainy years (available as a Biopesticide, Naturalis-T). Entomopathogenic nematodes (Steinernema carpocapsae or Heterorhabditis bacteriophora) can also suppress billbug populations.

Chemical control. In sites with a history of billbug problems, or where large numbers of adults where observed in spring or the preceding fall, preventative treatments against adults or larvae may be justified. The overwintered adults can be intercepted before egg-laying using short- residual insecticides. Use a liquid application with light post-treatment watering to keep the insecticide in the upper thatch where the adults reside. Systemic long-residual insecticides (e.g. imidacloprid, halofenozide), applied soon after adults become active in spring, control the larvae inside the plants. Curative treatment of the larvae can be done once the majority has move out of the plants into the soil (around mid-June). However, a lot of the damage may already be done at this point. III. Pests that suck juices and discolor leaves and stems

Several types of soft-bodied insects and mites suck juices from turfgrass plants with their sucking/piercing mouthparts. Generally, endophyte-enhanced ryegrasses and fescues are relatively resistant to many of these pests. Most of these pests occur in the foliar/stem zone where control can be optimized control with liquid applications and withholding irrigation and mowing for 1-2 days after application. If the pest lives mainly in the thatch (e.g., chinch bugs), either liquid or granular formulations can be used and should be moved into the thatch zone by using a higher spray volume or light post-treatment irrigation.

CHINCHBUGS, Blissus spp. (Hemiptera: Lygaeidae)

Pest status and plants attacked. 2 closely related species are important pest of turfgrasses. The hairy chinch bug, Blissus leucopterus hirtus, damages bentgrasses, bluegrasses, and fine- leaf fescues in the Northeast and upper Midwest. It also damages zoysiagrasses when grown in the cool-season zone. The southern chinch bug, Blissus insularis, is highly destructive to St. Augustine grass in the South.

Injury. Chinch bugs suck juices from stems and crown, causing gradual yellowing or dead patches of turf. In hot, dry springs damage caused by the 1st chinchbug generation may show up in June. Usually, the worst damage coincides with dry, hot periods in July and August.

Distribution. The hairy chinchbug occurs from VA northwards into Canada and westward to MN. The southern chinchbug occurs from SC westward to TX and southwards to FL.

Distinguishing characteristics. Hairy and southern chinchbug look very similar. Adults are about 1/16” long. The body is grayish-black and covered with fine hairs. The legs often have a dark, burnt-orange tint. The antennae are black, 4- segmented and easily seen. The wings are shiny white with a black triangular marking and are folded flat over the back, the tips overlapping. Adults occur in 2 types, short-winged (brachypterous) with wings extending only half the length of the abdomen, and long-winged (marcopterous) with wings extending the full length of the abdomen. Young nymphs are bright reddish-orange with distinct white bands across the abdomen. As the nymphs mature, they darken and develop wing pads.

Live history and habits. Life stages consist of egg, 5 nymphal instars, and the adult. From southern New England southwards, there are 2 generations per year. Adults overwinter in dense thatch, leaf litter, or similar sheltered places. They become active in early spring at about 50°F. Egg-laying begins in mid-April to May. Eggs are deposited in the thatch or in leaf sheaths. In New Jersey, egg-laying peaks from early May through early June (early bloom of white clover). The next generation of adults matures by about mid-July and lay eggs through late August. The second generation of adults matures September/October. Management. Chinchbugs are fairly easy to control if detected early. Monitoring can be done using the flotation method (open-ended cylinder pushed into the ground and filled with water to wash up the insects). The treatment threshold is considered as 20-25 nymphs per ft2.

Because chinchbugs thrive in thatchy lawn, reducing thatch discourages infestations. Irrigation during dry periods increases the turf tolerance for chinchbug feeding. Endophyte-enhanced cultivars pf perennial ryegrass and fescues are resistant to chinchbugs. Natural enemies include predatory mites, ground beetles, and parasitic wasp, and especially big-eyed bugs. The fungus Beauveria bassiana may kill more than 90% of the chinchbugs under favorable warm, moist conditions. The bioinsecticide Naturalis-T contains B. bassiana but the efficacy of this product still needs to be established.

Various short-residual insecticides can be used against chinchbugs. Either liquid or granular formulations can be used and should be moved into the thatch zone by using a higher spray volume or light post-treatment irrigation. Preventative treatments against overwintered females before egg-laying is often wasted, especially when cool and moist spring conditions lead to B. bassiana epizootics, and will also eliminate natural enemies. A more selective approach is to wait until June when the nymphs have hatched and spot-treat as needed.

IV. Pests that chew leaves and stems a. BLACK CUTWORM, Agrotis ipsilon (Hufnagel) (: Noctuidae)

Pest status and plants attacked. The black cutworm (BCW) is a major and perennial pest of close-cut creeping bentgrass on golf courses.

Injury. The larvae dig a burrow in the thatch or soil, or occupy coring holes and other cavities. They emerge at night to chew down the grass blades and stem around the burrow. This results in small dead patches and sunken areas. Bird foraging on the larvae may cause additional damage.

Distribution. Throughout most of North America.

Distinguishing characteristics. Adults are robust, hairy (wingspan 1 to 1-3/4”) with gray-black to dull brown forewings that bear a distinctive, black, dagger-shaped marking in the center. The hindwings are dirty white with dark veins. The larvae are hairless except for some bristles with a gray to nearly black upper side with a pale stripe down the middle of the back and a slightly lighter underside. Mature larvae are 1-1/4 to 1-3/4 in long.

Live history and habits. The life stages consist of eggs, 6-7 larval instars, pupa, and adult. There are 3 generations in the Middle Atlantic region and 2 generations further north. BCW cannot overwinter north of the transition zone and migrate from southern areas every spring, arriving around mid to late April. Damage from their offspring appears in mid to late May. Damage from the 2nd brood shows up from late June through July, and damage from the 3rd brood in late summer. The are nocturnal. Eggs are typically attached to tips of grass blades. The young larvae feed on the leaf blades. Older larvae form burrows in the thatch or soil from which they feed on the surrounding grass at night. On putting greens, larvae may wander up to 60 ft in a single night. Pupation occurs in the burrow.

Management. Regular monitoring is the key to effective BCW management. Commercial pheromone traps that attract only male moths can be used to determine treatment timing but are not correlated with larval densities in the turf. First damage can be expected 2 weeks after peak flight. Larval populations can be monitored with soap flushing solution (1 oz lemon-scented liquid dishwashing detergent in 2 gal of water). Application of the solution over a 1 yd2 area will flush BCW larvae and other insect to the surface within 5-8 min. Water the turf afterwards. Presence of 5-10 BCW larvae per yd2 may warrant treatment in lawns and fairways. The threshold may be much lower on greens and tees.

Endophyte-enhanced turfgrasses are not protected from BCW. Kentucky bluegrass, however, is a poor host, and may reduce BCW infestation if surrounding areas that are at risk. The nematode, Steinernema carpocapsae is fairly effective against BCW. Products containing Bacillus thuringiensis only control young larvae. For chemical control, liquid formulations should be used, applied as late in the day as possible, and not watered in for at least 24 h. Treating a 20-30 ft buffer zone around greens and tees will reduce migration from outlying areas. b. SOD WEBWORMS (Lepidoptera: Pyralidae)

Bluegrass webworm, Parapediasia teterrella; Larger sod webworm, Pediasia trisect;

Silverstriped webworm, Crambus praefectellus; Striped sod webworm, Fissicrambus mutabilis

Pest status and plants attacked. Sod webworm feed on all cool-season turfgrasses. New sod field and newly established lawns appear to be preferred sites. Serious damage can occur during drought conditions.

Injury. The large larvae chew off leaves and stems just above the crown. Weak or drought- stressed plants may be killed due to sun exposure of the exposed crown. Damage begins as general thinning, followed by patches of brown, closely-cropped grass.

Distribution. More than 20 species of sod webworm attack turfgrasses in North America. Damage seems to be greatest in the Midwest and eastern states.

Distinguishing characteristics. Life stages consist of egg, 6-8 larval instars, pupa, and adult. Adults are small dull-colored moths (wingspan ¾ to 1”). The front wings are mostly whitish, dull gray or tan, often with longitudinal stripes and other faint markings. The hindwings are usually lighter, whitish or light gray with delicate fringes on the outer margin. The wings are usually rolled around the body when at rest. Two small snout-like projections, formed by mouthparts, extend forward from the front of the head. The larvae are beige, brown, or greenish (depending on species) with a brownish head. Most species have characteristic dark, circular spots and coarse hairs scattered over the body. Mature larvae range from 5/8 to 1” in length.

Live history and habits. Most species have 2 or 3 generations per year. Temperate-zone sod webworms overwinter as partially grown larvae in silk-lined chambers in the thatch or soil. In spring they resume feeding, grow rapidly, and pupate. The emerging adults mate and the females lay eggs by dropping them during flight over the turf. Young larvae feed by scraping surface tissue for leaf blades but soon drop to the ground and make a tube-like, silken tunnel in the thatch or surface soil. Older larvae mainly feed at night, chewing down foliage around the burrow.

Management. Close inspection is the best way to confirm sod webworm presence. Soap flushes may also be used (see BCW). Generally 10-15 larvae per yd2 warrant control. Healthy, vigorous turf will often tolerate and outgrown damage from sod webworms. Endophyte- infected turfgrasses are relatively resistant to sod webworms. Sod webworms are fairly easy to control on a curative, or as-needed base. The best time to treat is 10-14 days after peak adult flight. Flight activity can be monitored with black light traps or pheromone traps for some species. The simplest monitoring tactic is to walk the turf at sunset after daytime temperature warm to 80°F and record the number of flying adults. The same products used for BCW control are also effective against sod webworms including entomopathogenic nematodes. To optimize control with chemical insecticides, liquid formulations should be used, applied as late in the day as possible, and not watered in for at least 24 h.

V. Recommended literature:

Brandenburg, R. L. & Villani, M. G. 1995. Handbook of turfgrass insect pests. The Entomological Society of America, Lanham, MD. 140 pp.

Potter, D. A. 1998. Destructive turfgrass insects: biology, diagnosis, and control. Ann Arbor Press, Chelsea, MI. 344 pp.

Tashiro, H. 1987. Turfgrass insects of the United States and Canada. Cornell University Press, Ithaca, NY. 391 pp.

Vittum, P. J., Villani, M. G., & Tashiro, H. 1999. Turfgrass insects of the United States and Canada. Cornell University Press, Ithaca, NY. 496 pp.

Watschke, T. L., Dernoeden, P. H. & Shetlar, D. J. 1995. Managing turfgrass pests. Lewis Publishers, Boca Raton, FL. 361 pp.

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