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123 - Good billbug hunting Simply looking for billbugs can...

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Unformatted text preview: . Good billbug hunting Simply looking for billbugs can help superintendents distinguish between turf disease and insect damage. David J. Shetlar, Ph.D. In the 19805, Ohio State turfgrass ento— mologist Harry Niemczyk. Ph.D.. called bill— bugs “one of the mosr commonly misdiag— nosed turf pests.” Billbugs have maintained that status into the let century. On golf courses, lawns and grounds or athletic fields, billbug damage is commonly mistaken for disease) drought or heat’stress; or damage caused by other insects such as white grubs, caterpillars or chinch bugs (45). North American billbugs are specific to either warm—season or cool-season turfgrasses. Billbugspecies ‘ ~—Cool—sea50n twfiras: pest: 7" > ' ‘ Most of the published information En bill— bug seasonal biology is based on the bluegrass billbug, which is found across most of North America (2,4). Though considered a cool’season turf pest. the bluegrass billbug has been found in noticeable numbers in several of the Gulf states. the; " '- " “ A3319?“ 9 es“. C Adult Sphenophoms parvulus, bluegrass billbug. The bluegrass billbug, Sp/amop/Jorur paruulur, and the lesser billbug, S. minimus. are common pests of cool—season turfs. Sp/aenop/yomparvulu: is about 5”6-inch long and has numerous fine punctures on the pronorum (the part of an insect’s body behind the head, the top surface of the pr0< thorax), but sometimes there is a medial ridge that runs down the center of the pronotum that has no punctures. The wing covers have smooth ridges that are also filled with small punctures. Spbenopborur minimur is usually a bit smaller (Winch) than S. parvulur, but the pronotal punctures are ofdisrinctly diEerent sizes and the wing covers appear crumpled with irregular ridges and punctures. SCIENCE FOR THE GOLF COURSE dedicated to enriching the environment of golf RESEARCH Warm-season rung-rats pests Hunting billbugs, S. vmatus, are larger billbugs, usually %— to 7/is—inch long, and have characteristically a raised ridge in the center of the pronotum that divides into a small fork just before reaching the head. This medial ridge is bracketed on each side with raised ridges that resemble parentheses. Hunting billbugs can vary considerably in color, from a deep red- brown color to completely black. Some believe that the brown forms are recently emerged insects, but that has not been established. The Phoenician billbug, S. phaem'rz'emir, seems to be more common than the hunting billbug in Arizona and Southern California, but both can be found in the same turf. , com 107 April 2003 Photo y Dave Shelia: Adult Sphentrphoms minimus, lesser blllbug Adult Spnenophorus venatus, hunting hillbug. Note the} raised ridge that is bracketed with two more raised ridges that resemble parentheses Sphenopnorus phoenicr'ensis, Phoenician brllbug, Note the raised areas on the mono turn that join to form a wide M-shaped pattern. 108 GGM . April 2003 Spbmap/aampbomidmis is 3/3— to 7As—inch long and looks much like the hunting billbug, except that the raised areas on the pronotum are expanded and join to form a wide M—shaped pattern. Tbefifl/j billbug A fifth billbug, S. cimtrirm'atm, is commonly called the Denver or Rocky Mountain billbug. This pest can be locally abundant in cool—season turf from New Mexico into Montana. It is a large species, often %—inch long or longer, with the appearance of black patent leather. The pronotum has numerous small pits filled with white hairs, and the wing covers have rows of heart—shaped pits, also filled with white hairs. Like the hunting billbug. this pest com— monly has larvae that feed during the winter months. Other species To firtther complicate the picture, I have found several other bill— bug species in North American turf, especially in the Southern states, and other entomologists have found additional species of billbugs in cool-season turfs. The most notable of these other species is 5. (confront, a large, 1/2-inch—long insect that looks much like the bluegrass billbug . and has no common name. I have found it in association with bermudagrass and St Augustinegrass from Oklahoma to Florida Its primary identifying characterisric [S that it looks like a bluegrass bill- bug but is twice the size life cycles Billbugs in cooleseasorr turf , The bluegrass billbug and lesser billbug have nearly identical life cycles. Although these billbugs prefer Kentucky bluegrass, they can easily infest perennial ryegrass and fine and tall fescues that do not contain endophytic fungi. The %—inch~long adults overwinter in turf and in weedy areas surrounding turf. In April and May, when daytime temperatures begin to reach 65 to 68 F on a regular basis, the adults mate and females seek out turf stems in which to insert their eggs. The females chew a hole at the base of turf stems and lay their eggs inside the turf stem. The eggs are generally white, bean—shaped, and about Vie-inch long. Within a few days, the eggs hatch into legless, grublikc larvae that first burrow up and down the stem in which they hatched. As the larvae grow, they molt within the stems and move downward toward the crown from late May into early June and can completely destroy crowns and new tillers by late June. Eventually the larvae destroy the crown and drop out of the stems once they become too large, about 3/16—inch long, to fit within the confines of the plant. By late June to early July when the mature larvae are about 3da-inch long, they dig downward into the soil, usually 1 to 2 inches, and form a pupal cell. Here, the pupae mature gradually over a two- week period. As new adults, they remain within the chamber for several days. New adults begin to appear in mid—July, and some of these may attempt a second generation. However, in most cases the summer-emerging adults appear to maintain themselves by peri— odically feeding at the bases of grass stems, but they do not cause visible damage to the turf. From late September into October, adults seek out sheltered sites in the turfgrass thatch or underlying soil for overwintering. Billbugr in warm-reamn turf Unfortunately, most of the other common billbug pests appear to have annual life cycles that are quite different from that of the bluegrass billbug. The hunting and Phoenician billbugs that prefer warm—season rurfs — especially bermudagrass and zoysiagrass — seem to have prolonged acrivity periods, with adults and larvae pre- sent over much of the season (3). From what has been observed of the hunting billbug, females chew holes into the stolons of bermuda— grass and zoysiagrass and insert their eggs. Upon hatching. the lat— vae feed briefly within the stolons and soon drop into the soil, where they feed externally on parts of their host grasses. The exact time needed for the larvae to complete their development is not currently known, but new hunting billbug adults first appear in late summer. However, by October, many billbug larvae are still present. Larvae of hunting billbugs commonly remain active during the winter as they continue feeding on dormant or slow—growing stolons and crowns. Because bermudagrass and zoysiagrass are dormant in winter, the extent of billbug damage will not be evident until the fol- lowing spring. In the spring, hunting and Phoenician billbug dam— age is often mistaken for spring dead spot disease or “delayed spring green- up syndrome. As the larvae mature, from February into early May they pupate, and the new adults lay eggs most of the summer. Because bermuda— grass: and zoysiagrass grow so rapidly during the summer, billbug lar- val damage 15 largely undetectable duri rig. the summer and early fall without digging in the turf or cutting it for sod. Although it is characterized as apest-Ofwarm-season tu rfgrasses, . the hunting billbug has been found? " more northern areas such as in cool— —season turf along the Atlantic coast. Paul Heller, Ph D at ' Penn State University stated that in 2002 he was called on to eval— uate a Pennsylvania sporrSi field infested with hunting billbugs. Jennifer Johnson- Cicalese Ph. 13., also has detected hunting billbugs regularly in New Jersey (1) In 2000 and 2001, researchers in Arkansas (E. Young and ]. Musiclt, unpublished data) attempted to assess the hunting billbug populations on golf course turf by setting out pitfall traps to sam‘ ple hunting billbug movement. They found that adult hunting bill- bugs are most often captured in pitfall traps in late March through late May, but they can be captured throughout most of the summer. Captured female billbugs were dissected, and their ovaries were rated for development (indicators of egg—laying potential) on a scale of zero to six (0 = no egg development evident; 6 = eggs ready to be laid). The relative size of their fat bodies (an indicator of nutritional health) and flight muscles located in the thorax (indicators of migra— tory behavior) were also rated. Ovarian development showed that hunting billbugs appeared to be ready to lay eggs from late March through mid—October. This implies that the females are probably laying eggs over much of the summer, thereby creating a large larval population by the time the bermudagrass is going dormant for the winter. Fat—body ratings sug— gest that the females are feeding throughout the summer and main- taining adequate nutrition for egg laying. Even though hunting billbugs rarely fly, it is interesting to note that their flight muscles reached maximum development in the spring period when the greatesr numbers of billbugs were captured in the pitfall traps. In short, the billbugs have stopped flying and have Adult Sphenophorus cicatfistr/‘arus, Denver or Rocky Mountain billbug Note the heart- shaped pits on the wing covers. Adun Sphenophorus GOES/irons BLUEGRASS BILLBUG LIFE STAGES 0'3 S o J} O N O Mean number/square foot to O _L 0 June July AUQUSt April May Bluegrass billbug life stages in Ohio as determined by weekly sampling l0f adults, eggs and larvae. RESEARCH turned to walking to move from one place to another, but their wing muscles still increase in size in the spring even though the billbugs no longer use them. Diagnosing billbug attacks In cool—season turf Diagnosing bluegrass and lesser billbug attack is very simple: Use the ”tug test.” To carry our the tug test, grab several of the affected stems and tug upward. In billbugvdamaged turf, stems will break off easily, just below the thatch level, and the bro- ken stems will be packed with a fine sawdust—like material, which is frass (or billbug feces). The real problem is determining which turf should undergo the tug test. Where Kentucky blue— grass, perennial ryegrass or fescues are used on the course — especially in the roughs, tee banks, green surrounds and bunker slopes -— billbug damage commonly will range in appearance from random dead grass stems (light infestations) to signs of early i , conditions (heavy infestations). Sloped areas with a sunny aspect’a’re mostoften at risk of showing The broken stems of turf damaged by billbug larvae will be packed with a line sawdusHike material, which are also the areas where suPerintendents usually - - is frass (or hillbug feces). , believe the turf damage is merely from drought or A D O o: O D Total billbugs L: (D a. 3 4- (‘3 L. d.) O. E '— —-— Total billbugs Temperature The total number of adult hunting blllhugs captured twice a week in traps on a golf course in Arkansas lrom March 22 to Dec. 2, 2001, and soil surface temperature (F), Graph courtesy of Brent Young and Jerry Musick, University of Arkansas, llfl GCM . April 2003 _ summer. dormancy, apparently caused by drought , 5 visual damage from billbugs. Unfortunately, these heat. Don‘t believe it without doing the tug test! In warm—reason turf Hunting and Phoenician billbug damage is most commonly Found in mowed roughs. tee banks. bunker slopes and other highsloped. sunny areas. As with the bluegrass billhug. damage in these areas is usually mistaken for lack ofirrigation, but it can also look like nematode activity, mole cricket damage, armyworm feeding or disease attack. in any case, find— ing the billbug larvae requires using a shovel to cut three sides ofa large flap of the turf and peel it back. Hunting billbug larvae are often an inch or more deep in the profile. Be watchful. All billbugs seem to like to “stroll” around. Hunting billbug adults — in groups of a dozen or more — are often seen walking across greens, espe cially in the late afternoon. These numbers indicate that MarB Apr19 May31 Juli? Augz3 Mar 29 May 10 Jun 21 Aug 2 Sep 13 —a— Ovarian maturity -e— Fat body Oct 4 NOV 15 001 25 —1— Flight muscle Mean weekly rating for ovarian. fat body and flight muscle development in the hunting billbug. Data were taken from insects trapped on an Arkansas golt course from March into November 2001. Sloped areas with a sunny aspect — such as this bunker slope attacked by bluegrass billbugs — are most often at risk of showing visual blllbug damage. April 2003 ncM iii liy or A'kansas. Graph courtesy of Hrr—ni Ynung and Jerry MuSle, [Inn-m mm by no. Nlemczyk RESEARCH a look at the surrounding sloped areas is in order. Billbugs often get trapped in bunkers, especially those with steep slopes. A walk around the edges of steep-walled bunkers will usually reveal some billbugs trying to climb out. Managing billbugs Control strategies are well defined and understood for the bluegrass billbug, but not for the hunting billbug. A Full range of options is available For controlling the blue‘ grass billbug: cultural controls (continuous irrigation and proper fertilization), plant resistance (endophyte—containing perennial ryegrass or fescues are toxic to billbugs), and preventive and curative insecticides. In cool— season turfgrass, regularly irrigated and fer~ or the billbugs commonly become infected with Beauoeria, a Fungal parasite of insects. E5?Fieldrestiarch .has also shown. that .billbu ’ ’ ' ' 5. up damaging PQPlllfifiori 7 dsthat Contain 40E) 50§ercent endnphytelinfeetionsf i. W: 7 ' .. " ' Preventive application: tilizecl turf seems to outgrow billbug damage . Tlpounds a.i./ac1'e. damage, superintendents often apply a sur— face» or thatch—targeted insecticide in late April to mid-May to kill the overwintered adults that are looking for places to lay their eggs. Chlorpyrifos (Dursban) and most of the pyrerhroids (for example, DeltaGard, Scimitar, Tempo, Talstat, etc.) are useful in this mode. lmidacloprid (Merit) and halofenozide (MACH 2) are good at pre— venting billbug damage if they are applied in May when the adults are laying eggs. [t is uncertain whether these insecticides are killing the bluegrass billbug adults or whether their residues are killing the larvae, but these early applications prevent damage. Note that Merit is to be used at the 0.4 pound a.i./acre rate if billbugs are the pri— mary target (there should be enough residual to kill black turfgrass ataenius and the normal annual grub species that arrive in July), and MACH 2 labels now recommend using 2.0 Fogrpryeventive control ofhuntingi bill— _ugs, 1‘???“ research Frqm' Arkansas in spring. hunting hillbug damage in bermudagrass is often mistaken for spring dead spot disease or “delayed spring green-up syndrome." 112 oeM , April 2003 ounginid J. Musick, unpubhshed) suggests that mostadults are active'froindate; March, through July, but adult females may be lay— ' Jr, , ,- . r—To-ipreVent bluegrass and lesser-bulking: .Jing. eggs, from April into mid-October. J+(Mocap);bt'i'tlthe'seare'no' longer available: Therefore, an application of an insecticide that kills the adults or the early—stage larvae From April through June should provide pro- tection from the damage observed in the fol- lowing winter or spring. My experience is that imidacloprid (Merit) applied during this time has eliminated much of the hunting billbug damage observed on tee banks and bunker slopes. One might consider making this application when mole cricket eggs are hatching or annual white grubs are laying their eggs in order to reduce the populations of these insects at the same time. Curative control Curative control of bluegrass and lesser billbugs in mid— to late June is difi‘icult at best. The only product that remains as a potential billbug curative control is carbaryl (Sevin). In the past, isophenfos (Oftanol) and isazofos (Triumph)‘were used successfiilly, but neitherds ‘ i ah .sent‘e' superin— R a , ‘ . shillbugShas'héén‘iéhiEVéd’ih Oftanol, Triumph and ethoprop i i, Acknowledgments; ~ nah-lananrnfgon'ofnigaa—tantalising 51: vidingpar'tial s'ufiport‘lor biltbugrstudy:_$peciailhanl<s go to Jerry Musiok and Brent Young at the University of Arkansas for sharing their knowledge of the hunting billbug and providing graphs of their findings. Literature cited 1. Johnson~Cicalese, J.M.. GW. Wolfe and CR. Funk. 1990. Biology, distribution. and taxonomy of billbug turf pests (Coleoptera: Curculionldae). Environmental Entomologist 1 9:1037—1 046. 2. Kindler, 8D,, and SM. Spomer. 1986. Observations on the biology of the bluegrass billhug, Sphenopnorus parvulus Gyllenhal (Coleoptera: Curculionidae), in an eastern Nebraska sod field. Journal of the Kansas Entomological Society 59:26-31 . 3. Morishita, ES, W. Humphrey, L.C. Johnston and RN. Jefferson. 1971. Control of billbugs in turf. California Turfgrass Culture 21 (2):1 3-1 4. 4. Niemczyk. H0. and D.J. Shetlar. 2000. Destructive turl insects, 2nd ed. HDN Books. Wooster, Ohio. 5. Vitlum, P.J., MG Villani and H. Tashiro. 1999. Turigrass insects of the United States and Canada, 2nd ed, Cornell University Press, Ithaca, NY. David J. Shetlar, PhD. ([email protected]). is an asso- ciate professor of entomology at Ohio State University, Columbus. ...
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