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Resistant Turfgrasses forImproved Chinch Bug ManagementUniversity of Nebraska researchers document multiple chinch bugresistance in cool- and warm-season turfgrasses.BY TIFFANY M. HENG-MOSS, F. P. BAXENDALE,R. C. SHEARMAN, AND T. E. EICKHOFF

Researchers at the University of Nebraska evaluated selected cool- and warm-season turfgrasses forresistance to chinch bugs in the Blissus complex, and documented the presence of multiple chinch bugresistance in these turfgrasses.

Numerous arthropods areimportant pests of the cool-and warm-season turf grasses

commonly found on golf courses. Turf-grasses are subject to injury by insectand mite pests, and several are known tohave increased susceptibility to certainsap-feeding insects, including chinchbugs.

In the United States there are fourchinch bug species that are of majoreconomic importance: common chinchbug (Blissus leucopterus leucopterus),southern chinch bug (Blissus insularis),hairy chinch bug (Blissus leucopterus),and western chinch bug (Blissusocciduus).8 Chinch bugs are widely dis-tributed throughout the United States,primarily east of the Rocky Mountains.Individual species often have overlap-ping geographic distributions. In par-ticular, the geographic distribution ofthe western chinch bug, and its pre-ferred host, buffalograss, are such thatany of the other chinch bug speciescould be present in adjacent turfgrasses.Furthermore, all four chinch bug specieshave extensive documented host ranges.

The common chinch bug is widelydistributed across the east coast andwestern plains of the United States andsouth in Mexico. The most commonhosts of this chinch bug include wheat,sorghum, corn, and several turf grasses(bermudagrass, Kentucky bluegrass, tallfescue, and zoysiagrass).

The hairy chinch bug is distributedthroughout the northeastern UnitedStates. Its range includes southernregions of the eastern Canadianprovinces, parts of the Midwest toMinnesota, and into the Mid-AtlanticStates as far south asVirginia. It is animportant pest of most cool-seasonturf grasses, including creeping bent-grass, Kentucky bluegrass, perennialryegrass, and fine-leaf fescues. The hairychinch bug is also an occasional pest ofzoysiagrass and St. Augustinegrass, and it

has been reported feeding on timothygrass.

The southern chinch bug ranges fromsouthern North Carolina southward tothe Florida Keys and into eastern andsoutheastern portions of Texas. Thischinch bug is considered the most de-structive pest of St. Augustinegrass. Italso occasionally infests bahiagrass, ber-mudagrass, centipedegrass, and zoysia-grass, and it has been reported feedingon crabgrass, guineagrass, pangolagrass,torpedograss, and tropical carpetgrass.

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Chinch bugs are widely distributed throughout the United States, primarily east of the Rocky Mountains. Individual species often have overlapping geographicdistributions. Shown, left to right, are the distribution of common chinch bugs, hairy chinch bugs, southern chinch bugs, and western chinch bugs.

The distribution of the westernchinch bug includes much of the cen-tral United States, north into Canada,and south into Mexico. First detectedinfesting a heavily damaged buffalograsslawn in Lincoln, Nebraska, in 1989,these chinch bugs have subsequentlybeen found associated with buffalograssthroughout Nebraska and surroundingareas.3 More recently, the westernchinch bug has become a pest ofZOYSlagrass.

Recent studies at the University ofNebraska have shown that this chinchbug has an extensive host range, includ-ing buffalograss, zoysiagrass, Kentuckybluegrass, tall fescue, bermudagrass, andperennial ryegrass.4 Among the turf-grasses tested, offspring were producedon buffalograss, fine fescue, perennialryegrass, bentgrass, zoysiagrass, Kentuckybluegrass, and tall fescue, demonstratingthat the western chinch bug can repro-duce on a wide variety of hosts. Theseresults have profound implications and

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provide new information that willfacilitate improved monitoring anddetection of chinch bug infestationsbefore they build to damaging levels.Increased knowledge of the biologyand host range. of this chinch bug willaid in the development of moreefficient management approaches.

BASIC CHINCH BUGBIOLOGYThe immature stages of all chinch bugspecies are similar in appearance. Chinchbug eggs are elongate, whitish, andaverage < Y25 inch (1.0 mm) in lengthwhen first laid. As the embryo develops,the egg takes on an orange-red color,with the nymphal chinch bug visiblewithin the egg before hatching. Firstins tars are tiny « Y25 inch), long, bright-red insects with a distinctive white bandacross the abdomen. As nymphs maturethrough five nymphal stages, their colorgradually changes to orange-brown andfinally to dark brown. Adults are black

with reddish-yellow legs and are aboutYto to 116 inch, depending on the sex andspecies. Females are typically larger andmore robust than males.

Most chinch bug adults have shinywhite wings that extend back over theabdomen, but wing dimorphism iscommon, with both macropterous(long-winged) and brachypterous(short-winged) forms present in certainspecies. Chinch bugs tend to feed inaggregations and often produce a char-acteristic odor from scent glands whendisturbed or crushed. Most chinch bugspecies have two generations per yearand overwinter as adults.

Chinch bugs injure grasses by with-drawing sap from plant tissues in thecrown area. While feeding, they alsomay inj ect a salivary toxin that damagesplant tissues and inhibits the transloca-tion of water and nutrients. Initially, thisfeeding results in reddish-purple dis-coloration of the leaves. In the turfstand, damage appears as patchy areas

that turn yellow and dry to a straw-brown color as feeding progresses. Athigher infestation levels, chinch bugfeeding can result in severe thinning ordeath of the turfgrass stand.

Damage is usually the heaviest insunny locations during hot, dry periodsand is often mistaken for drought stress.Chinch bug infestations are less likelyto develop in years when spring andsummer rainfall and temperature arenear or below normal. This occurs inpart because fungal diseases keep chinchbugs under control. These diseases aremuch less likely to develop duringperiods of drought, and followingseveral dry seasons chinch bug numberscan build to damaging levels.

PLANTRESISTANCEHistorically, insecticides have beenemployed as the principal method tocontrol chinch bugs. However, concernfor reducing pesticide inputs has under-scored the need for developing alterna-tive approaches for controlling insect

pests affecting turfgrasses. One suchapproach involves the use of integratedpest management (IPM). This strategyemploys all suitable techniques in ascomplementary and environmentallycompatible a manner as possible tomaintain pest populations below dam-aging levels. IPM tactics include cultural,mechanical, biological, and chemicalcontrols, and the use of plant resistanceto insects. The development of turf-grasses with resistance to chinch bugsoffers an attractive approach for manag-ing insect pests associated with turf-grasses because it is sustainable andenvironmentally responsible.

The idea behind plant resistance is toexploit natural plant defense systems.Turfgrasses possess a variety of naturaldefense mechanisms to overcome bioticstresses such as insect feeding. Thesedefense mechanisms can be based onphysical or chemical characteristics ofthe turfgrass. In some cases, the turf grassis able to tolerate insect feeding throughphysiological and biochemicalmodifications .

Turfgrasses with resistance to thechinch bug species have been identifiedin both cool- and warm-season turf-grasses. However, few of the recentlyreleased cultivars have been evaluatedfor chinch bug resistance, and it remainsunclear if turf grasses with resistance toone chinch species may also be resistantto one or more of the other species.The USGA helped to fund a projectthat focused on evaluating selectedcool- and warm-season turf grasses forresistance to chinch bugs in the Blissuscomplex, and documenting any inci-dence of multiple resistance. This infor-mation is fundamentally important fordeveloping chinch bug-resistant turf-grasses through conventional breedingand biotechnological techniques.

RESISTANCE TO THEWESTERN CHINCH BUGGreenhouse and field screening studieswere initiated to search for buffalo-grasses, bermudagrasses, and zoysia-grasses with resistance to the westernchinch bug. Forty-eight buffalograss

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genotypes from diverse geographicallocations were evaluated in replicatedstudies under greenhouse conditions.Based on turfgrass damage ratings,4 were categorized as higWy resistant,22 were moderately resistant, 19 weremoderately susceptible, and 3 werehigWy susceptible to chinch bugfeeding. 5,6

Of the buffalograsses studied,"Prestige" exhibited minimal chinchbug damage, although it became heavilyinfested with chinch bugs. This suggeststhat tolerance may be responsible forthe resistance.7 Plant tolerance hasseveral advantages as a pest managementtool from an ecological viewpoint: itraises economic/aesthetic injury levels,preventing early pest managementaction, and does not place selectionpressure on pest populations, unlike

other management approaches. In spiteof its advantages, the use of tolerancefor pest management is limited primarilybecause the mechanisms and genetics ofplant tolerance remain unknown.

Studies are currently underway toinvestigate the biochemical and physio-logical mechanisms imparting resistancein buffalograss. This information is fun-damentally important for formulatingplant breeding strategies and subse-quently developing chinch bug-resistantturf grasses through conventional breed-ing and biotechnological techniques. Inaddition, knowledge of specific resis-tance mechanisms would be valuablefor identifying biochemical and physio-logical markers for use in germplasmenhancement programs and for charac-terizing plant defense strategies toinsect feeding.

Several zoysiagrasses and bermuda-grasses were also evaluated for resistanceto the western chinch bug. The zoysia-grass "Emerald" and bermudagrass"Mini Verde" displayed the highest levelof resistance, while the zoysiagrasses"Myer," "Zenith," "DeAnza," and thebermudagrasses "Jackpot" and "Tifway419" were moderately to higWy suscep-tible to chinch bug injury.

MULTIPLE CHINCH BUGRESISTANCEAnother component of this research wasto document the presence of multiplechinch bug resistance among selectedcool- and warm-season turf grasses.Because of the extensive geographicaloverlap of the four economicallyimportant chinch bug species and theirhost plants, the' potential exists for the

The immature stages of all chinch bug species are similar in appearance. Chinch bug eggs are elongate, whitish, and average < Y2s inch (1.0 mm) in lengthwhen first laid.As the embryo develops, the egg takes on an orange-red color, with the nymphal chinch bug visible within the egg before hatching. First instarsare tiny, < Y2s inch (1.0 mm) long, bright-red insects with a destinctive white band across the abdomen. As nymphs mature (there are five nymphal stages),their color gradually changes to orange-brown and finally to dark brown. Adults are black with reddish-yellow legs and are about Y;o to 'l'I6 inch (2.5 to 5mm), depending on the sex and species. Females are typically larger and more robust than males.

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Researchers at the University of Nebraska are investigating chinch bug damage. Recent studieshave shown that the western chinch bug has an extensive host range, including buffalograss,zoysiagrass, Kentucky bluegrass, tall fescue, bermudagrass, and perennial ryegrass.

western chinch bug and other chinchbug species to become associated withand damage non-traditional turfgrasses.The presence of turf grasses with resis-tance to multiple chinch bug specieswould be highly desirable in theseinterfacing situations.

A series of studies was conductedunder greenhouse conditions to evalu-ate selected buffalograsses, fine fescues,and St. Augustine-grasses for resistance tomultiple chinch bugspecies. These studiesestablished thatbuffalograsses resistantto the western chinchbug were susceptibleto southern and hairychinch bugs. All St.Augustinegrasses(southern chinch bug-resistant "Floratam"and -susceptible"Raleigh" and"Amerishade") werehighly resistant to thewestern chinch bug.Furthermore, allendophyte-free and-enhanced fine fescueswere moderately tohighly susceptible to the hairy chinchbug, but moderately to highly resistantto the western chinch bug. This researchclearly demonstrates multiple resistanceamong turf grasses to chinch bugs andsuggests different feeding mechanismsamong the chinch bug complex. 1

The varying degrees of susceptibilityand resistance exhibited by the grassesunderscores the importance of identify-ing turf grasses that are not only resistantto one particular chinch bug species,but also resistant to other chinch bugspecies inhabiting nearby turf areas. Forexample, as buffalograss is adapted tovarious regions throughout the UnitedStates, it is likely to be planted nearareas of southern and hairy chinch buginfestations. Therefore, identifYing turf-grasses that exhibit resistance to multiplechinch bug species will decrease the

chances of an opportunistic infestationby southern and hairy chinch bugs.

The reasons for the different responsesof the grasses to the three chinch bugsremain unclear. Studies investigatingchinch bug probing behaviors, feedinglocations, and mouthpart morphologyhave documented differences in probingfrequencies among the chinch bugspecies and identified the vascular tissues,

bulliform cells, and bundle sheaths asprimary chinch bug feeding sites. 1

Scanning electron micrographs revealedno obvious differences in the mouth-part morphology among Blissus speciesand subspecies.2 Studies are currentlyunderway to identify and characterizechinch bug salivary secretions, anddocument differences among thechinch bug species.

This research provides essential infor-mation for the development of chinchbug-resistant buffalograsses for use ongolf courses and other turfgrass areas,and for the implementation of chinchbug management decisions. Commercialproduction of warm-season turf grasseswith resistance to chinch bugs will offerturf grass professionals and homeownerswith a high-quality turfgrass withenhanced resistance to chinch bugs.

LITERATURE CITED1. Anderson, W G., T. M. Heng-Moss, and F. P.Baxendale. 2005. Evaluation of cool- and warm-season grasses for resistance to multiple chinchbug (Hemiptera: Blissidae) species.] ECMI.

Entomol. (Accepted).

2. Anderson, W G., T. M. Heng-Moss, F. P.Baxendale, L. M. Baird, G. Sarath, and L. G.Higley. 2005. Chinch bug (Hemiptera: Blissidae)mouthpart morphology, probing frequencies,and locations on resistant and susceptiblegermplasm.] Econ. Entomol. (Accepted).

3. Baxendale, F. P., T. M.Heng-Moss, and T. P.Riordan. 1999. Blissusocciduus (Hemiptera:Lygaeidae): a chinch bugpest new to buffalograssturf.] Econ. Entomol.92:1172-1176.

4. Eickhoff, T. E., F. P.Baxendale, T. M. Heng-Moss, and E. E.Blankenship. 2004.Turfgrass, crop, and weedhosts of Blissus occiduus(Hemiptera: Lygaeidae).]Econ. Entomol. 97:67-73.5. Gulsen, 0.,T. Heng-Moss, R. Shearman, P.Baenziger, D. Lee, and F.Baxendale. 2004.Buffalograss germplasmresistance to Blissus occiduus(Hemiptera: Lygaeidae).]Econ. Entomol. 97:2101-2105.

6. Heng-Moss, T. M., F. P.Baxendale, T. P. Riordan,

and J. E. Foster. 2002. Evaluation of buffalograssgermplasm for resistance to B. occiduus(Hemiptera: Lygaeidae).] Econ. Entomol.95: 1054-1058.

7. Heng-Moss, T. M., F. P. Baxendale, T. P.Riordan, L. Young, and K. Lee. 2003. Chinchbug-resistant buffalograss: an investigation oftolerance, antixenosis, and antibiosis.] Econ.Entomol.96:1942-1951.8. Vittum, P. J., M. G. Villani, and H. Tashiro.1999. Turfgrass Insects of the United States and'Canada. Second edition. Cornell UniversityPress. Ithaca, N.Y

TIFFANY M. HENG-MOSS, PH.D.,

Assistant Professor,Department of Ento-mology; FREDERICK P. BAXENDALE,

PH.D., Prcgessor,Department of Entomology)'ROBERT C. SHEARMAN, PH.D., Prcgessor,Department ofAgronomy and Horticulture;and THOMAS E. EICKHOFF, GraduateResearch Assistant) Department of Ento-mology, University of Nebraska) Lincoln.

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