Great Basin Naturalist

Volume 47 Number 4 Article 25

10-31-1987

Herbivorous and parasitic guilds associated with Great Basin wildrye (Elymus cinereus) in southern Idaho

Berta A. Youtie University of Idaho, Moscow, Idaho

Michael Stafford University of Idaho, Moscow, Idaho

James B. Johnson University of Idaho, Moscow, Idaho

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Recommended Citation Youtie, Berta A.; Stafford, Michael; and Johnson, James B. (1987) "Herbivorous and parasitic insect guilds associated with Great Basin wildrye (Elymus cinereus) in southern Idaho," Great Basin Naturalist: Vol. 47 : No. 4 , Article 25. Available at: https://scholarsarchive.byu.edu/gbn/vol47/iss4/25

This Article is brought to you for free and open access by the Western North American Naturalist Publications at BYU ScholarsArchive. It has been accepted for inclusion in Great Basin Naturalist by an authorized editor of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. HERBIVOROUS AND PARASITIC INSECT GUILDS ASSOCIATED WITH GREAT BASIN WILDRYE {ELYMUS CINEREUS) IN SOUTHERN IDAHO'

Berta A. Youtie", Michael Stafford", and James B. Johnson

Abstract — inhabiting Great Basin wildrye {Elymiis cinereus Scribn. & Merr.) were surveyed at two sites on the Snake River Plain in southern Idaho during 1982 and 1983. Forty-six species of phytophagous insects were observed. In addition, eight parasitoid species were reared from insect hosts in the plant culms and identified. Life stage, abundance, plant part utilized, and study site were recorded for each insect species collected. Insect guilds at the two sites were compared based on species presence utilizing Sorensen's similarity index. Overall, 26 insect species were common to both sites, yielding a moderate similarity index of 0.62. The majority of the species that constitute the wildrye herbivore guilds were oligophagous (restricted to grasses). Many of these insects feed on grain crops as well as other native and introduced grasses. The relatively high diversity of phytophages on wildrye mav be due to its tall, bunchgrass growth form, its abundance within its habitat, its broad geographic range, and the large number of related species of grasses in the region.

Great Basin wildrye {Elymus cinereus brush {Artemisia tridentata subsp. wyomin- Scribn. & Merr.) is one of the largest and most gensis ). The second site was located in widespread native bunchgrasses in the west- the north end of Craters of the Moon National ern U.S. (Lesperance et al. 1978). It is an Monument (CRMO), 29 km southwest of Arco important component of both the salt desert at 1,817 m elevation. The precipitation is al- shrub and sagebrush/grass ecosystems. Every most twice as abundant at this site (426 mm/ spring and summer the plant produces enor- yr). Wildrye grew on an 8.5-ha, relatively wet mous amounts of biomass that may be ex- meadow that was surrounded by mountain big ploited by vertebrate and invertebrate herbi- sagebrush {Arte7nisia tridentata subsp.

vores. Much is known of wiklrye's palatability vaseyana [Ryberg] Beetle). and utilization by large ungulate grazers Insects were monitored on the host plant (Perry and Chapman 1974, 1975, Krall et al. from its three-leaf phenological stage in May 1971, Lesperance et al. 1978, Murray et al. through seed maturation in late August. Fif- 1978), but there has been no comprehensive teen plants were randomly selected along two study of its phytophagous insect communi- random, 50-m transects at each site at weekly ties. An attempt was made to partition the intervals. The insect fauna on each host plant plant into anatomical regions and identify the was observed for five minutes. Insect life associated insect herbivore guilds and their stage, behavior, relative abundance, and parasitoids. The impacts and diversity of these plant parts utilized were recorded. Insects guilds are discussed. were hand-picked or aspirated from the grass for later identification. Presence of internal determined by dissecting five Methods feeders was tillers from each plant. Each week five plants Insects associated with Great Basin wildrye at each site were excavated, examined for were surveyed at two sites on the Idaho Snake root- and root-crown-infesting insects, and resi- River Plain during 1982 and 1983. The 1. 1-ha, placed into Berlese funnels to collect the lower-elevation (1,475 m), and drier (246 mm dent insects. precipitation/yr) site was located on the Idaho Insect feeding was determined by direct National Engineering Laboratory (INEL), 10 observation such as mouthpart insertion and km south of Howe, Butte Co. Wildrye occu- plant damage. While not absolutely definitive pied low, saline areas surrounded by higher in all cases, this method is more accurate than ground that supported Wyoming big sage- previous sweep-net sampling programs

'Published with the approval of the director of the Idaho Agricultural Experiment Station as Research Paper No. 87714. ^Department of Plant, Soil and Entomological Sciences, University of Idaho. Moscow, Idaho 8.3843.

644 October 1987 YOUTIE ETAL.: WiLDRVE INSECTS IN IDAHO 645

(Horning and Barr 1968). likely that the larvae belonged to this species.

Culm- and Leaf-Feeders Results and Discussion A large number of herbivores utilize both Forty-six insect species in 22 families and the culms and leaves of grasses; therefore, seven orders were identified as feeding on these two anatomical regions are discussed wildrye. Each species was categorized as to together. Grasshoppers are one of the most abundance, life-stage feeding on wildrye, re- common and destructive groups of insects on gion of the host plant utilized, and host western ranges (Watts et al. 1982). They are specificity (Table 1). Eight species of para- the most visible pests and have been studied sitoids were also reared from insect hosts in more than any other graminivorous insects. the culms and identified (Table 2). The host Five species of acridids were collected on plant was partitioned into five anatomical wildrye during the summers of 1982 and 1983. components: roots, culms, leaves, flowers, Four of these species are in the genus and seeds. Each region supported a variety of Melanoplus, with the migratory grasshopper, insect species that employed different feeding M. sangtiinipes, being most abundant. strategies. Many of the insects utilized more A few were also found to be external than one plant part and thus were identified in chewers. Adult Dichelonyx fed on the host more than one guild. plant in July at CRMO. Anisostena califor- nica, a chrysomelid, was observed Root-Feeders feeding on wildrye leaves at both sites. Aphids, mealybugs, and beetle larvae were Larvae of three species of Hymenoptera fed the most abundant insects feeding on wildrye internally in the grass culm. Cephus cinctiis roots. The aphids, Forda marginata and F. larvae tunneled down the stems consuming olivacea, were collected in low numbers in parenchyma and vascular tissues. Larvae the spring and early summer. Both species eventually cut the stems and overwintered in have been reported to feed only on grass roots the remaining stubs. Sawfly herbivory may and are associated with ant nests (Gillette impair transport of water and nutrients 1918, Patch 1939, Gittins et al. 1976, Smith through the stem, thus detrimentally affect- and Parron 1978). Two pseudococcids were ing grain production (Holmes 1977, Seamans less frequently collected on the roots of the et al. 1944). Jointworms, Tetramesa spp., host plant. One, Crijptoripersia trichura, is were reared from wildrye culms. Tetramesa known to inhabit grass roots in Arizona and larvae fed on internal tissues. At least one New Mexico (MacGillivray 1921). species formed "bump galls" on the stem be- Elaterid larvae, wireworms, were very low the inflorescence. Spears and Barr (1985) common in the soil surrounding the roots and reported that these larvae adversely affect the are known as major pests of grains and range growth and reproduction of several range grasses. Chafer larvae, Dichelonyx sp., and grasses. Dipteran larvae, probably chloro- adult weevils, Brachyrhinus ovatus, were pids, were also collected within the stems but found to infest Great Basin wildrye roots at could not be reared to adults.

CRMO. Adult billbugs, Sphenophorous gen- Although injury due to defoliators is more tilis, were very common on the seed heads of apparent, fluid-feeding Homoptera and E. cinereus at INEL. Billbug larvae are Hemiptera may have the greatest impact on known to feed on the roots of a variety of wildrye and other native grasses (Haws 1982). grasses (Asay et al. 1983, Tashiro and Person- By extracting plant fluids and pumping saliva ius 1970, Kamm 1969) and were believed to into the plant, these insects remove essential feed on the roots of wildrye at the study site, plant sap and cytoplasm and may inject toxic but could not be located. Cerambycid larvae compounds or transmit viruses. Cicadas, were collected in the root masses of wildrye Okanogana bella, were very visible in the and identified to the subfamily . summer clinging to wildrye stems at CRMO. Cortodera barri, a cerambycid commonly ob- Leafhoppers and delphacids were the most served feeding on wildrye pollen as an adult, common insects feeding on wildrye. Over 50 was the only species belonging to this subfam- individuals of a delphacid, Eurysa ohesa, ily found in the area. Therefore, it seems were counted at one time on an individual 646 Great Basin Naturalist Vol. 47, No. 4

Table 1. Insects collected and observed feeding on Great Basin wildrye at Craters of the Moon National Monument (C) and the Idaho National Engineering Laboratory Site (I) in 1982-83.

Taxa Life stage^ Plant parts' Location Host spec." Abundance Orthoptera Acrididae Melanopltis bivittatus (Say) n, a Melanophis femurrubrum (DeGeer) Melanoplus foediis Scudder Melanopltis sanguinipes (Fabricius) Phoetaliotes nebrascensis (Thomas)

Thysanoptera Aeolothripidae Aeolothrips auricestus Treherne Aeolothrips sp. Thripidae Aptinothrips rufus (Gmelin) Frankliniella occidentalis (Pergande) Frankliniella sp. Sericothrips sp.

HOMOPTERA Cicadidae Okanogana bella Davis Cicadellidae Dikraneura carneola (Stal) Hecahis viridis (Uhler) Delphacidae Eurysa obesa Beamer Aphididae Forda marginata (Koch) Forda olivacea Rohwer Pseudococcidae Cryptoripersia trichura (Cockerell) Phenacoccus sp. Trionymus smithii (Essig) Eriococcidae Eriococcus insignis Newstead

Hemiptera Miridae Irbisia pacifica (Uhler) Labops iitahensis Slater Litomeris debilis (Uhler) Stenodenia laevigatum (Linnaeus) Pentatomidae Aelia americana Dallas Rhytidilomia uhleri Stal

Coleoptera Elateridae Anchastus cinereipennis Eschscholtz Cardiophorus sp. Limonius infuscatiis Motschulsky Limonius sp. Melyridae Attains glabrellus Fall Attains rnortdus smithi Hopping Collops bipunctus (Say) Anthicidae Notoxus serratus LeConte Phalacrus pencillatus Say Dichelonyx sp. October 1987 YOUTIE ET AL.: WiLDRYE INSECTS IN IDAHO 647

Table 1 continued.

Ta\a Life stage'' Plant parts' Location Host spec' Abundance'' Cerambycidae Cortodera barri Linsley & Chemsak r

Chrysomelidae Alt tea sp. Anisostcna californica Van Dyke Curculionidae Brachyrhiniis ovatiis (Linnaeus) Sphenophorus gentilis LeConte

Lepidoptera Noctuidae Faronta diffusa (Walker) Hymenoptera Cephidae CephtiS cinctus Norton Eurytomidae Tetramesa ehjmophaga (Phillips) Tetramesa sp. 648 Great Basin Naturalist Vol. 47, No. 4

Table 3. Sorensen coefficients of insect community similarity by guild on Great Basin wildrye at Craters of the Moon National Monument (CRMO) and the Idaho National Engineering Laboratory (INEL) in 1982 and 1983. October 1987 YOUTIE ETAL: WiLDRYE INSECTS IN IDAHO 649

Wildrye, a large, structurally diverse plant, feed on wildrye are likely to feed on alternate supports a sizable fauna and thus may serve as hosts in related genera, thus increasing the a reservoir for many of these herbivores. geographical area they may exploit. However, wildrye stands also may function as Insect species found on a particular host reservoirs for potentially useful predator and plant are influenced by the local abundance of parasite species. the plant, both its density and extent (Strong The number of phytophagous insect species et al. 1984, Fowler and Lawton 1982, Root exploiting Great Basin wildrye was quite large 1973). On the study sites wildrye grew in relative to other native grasses in the area. almost pure stands, but in very different habi- Very few studies have identified the total phy- tats. Wildrye has a large geographic range, tophagous insect community associated with grows in a variety of habitat types (Walker and an individual grass species. Watts (1963) col- Brotherson 1982), and is locally abundant lected 120 species on black grama grass, within these types. Insects feeding on this Bouteloua eriopoda Torrey; however, these grass find a large, conspicuous food source included grass-feeders, parasites and preda- that remains available longer into the summer tors, and casual visitors. Wight (1986) than any other C3 grass species in the area. identified 33 phytophagous insects on the in- Graminivorous insects were identified that troduced crested wheatgrass, Agropyron have the potential to reduce forage and seed cristatum (L.) Gaertn., in southern Idaho. production of wildrye. This information may Beisler and his colleagues (1977) collected be valuable to grass breeders, seed compa- phytophagous insects associated with three nies, and range managers interested in reveg- weedy grasses. They found 33 species feeding etation of certain types of rangelands with on Johnson grass. Sorghum halepense (L.) basin wildrye. Some of the phytophagous in- Pers.; 39 on fall panicum, Panicum di- sects in this study apparently reduced repro- chotomiflorum Michx. ; and 35 associated with ductive potential of wildrye and may have large crabgrass, Digitaria sanguinalis (L.) detrimental effects on reseedings. Although Scop. grasses are very tolerant of herbivory and Plant structural diversity, species area rela- have evolved many means of tolerating graz- tionships, and taxonomic isolation are thought ing (McNaughton 1979, Stebbins 1981), in- to explain much of the richness of insect spe- sect populations fluctuate greatly and in some cies on a host plant (Lawton and Schroder years could reach injurious levels. Therefore,

1977, Southwood 1961, Strong and Levin it is important to identify which plants and 1979). Grasses and forbs are less structurally plant parts are fed upon by various members diverse than trees and shrubs and usually of the insect community and to determine the have fewer associated species (Niemela et al. impact of herbivory on an individual plant

1982, Strong et al. 1984). However, wildrye's species and its population dynamics. height and foliage diversity provide a greater variety of microhabitats than do most range Acknowledgments grasses. Tallamy and Denno (1979) found the more structurally complex grass Distichlis spi- We thank O. D. Markham, U.S. Depart- cata (L.) Greene supported a richer commu- ment of Energy, Idaho National Engineering nity of sap-feeders than the simpler Spartina Laboratory Site, and the staff at Craters of the alterniflora Loisel. Moon National Monument for their coopera- Taxonomically isolated plants may have im- tion and logistical support. We appreciate the poverished insect faunas (Strong et al. 1984). helpful suggestions of Drs. J. P. McCaffrey Wildrye belongs to the grass tribe Triticeae. and M. A. Brusven, University of Idaho, Idaho is included as one of the areas of the while preparing this manuscript. Apprecia- world with the greatest concentrations of spe- tion is also extended to Frank Merickel, Uni- cies in this tribe (Hartley 1972). Therefore, versity of Idaho, and the many other entomol- many closely related grass genera, such as ogists who assisted in identifying specimens. Agropyron, Sitanion, and Hordetim, are well This study was funded by the University of represented in the area. Many insects that Idaho, College of Agriculture. 650 Great Basin Naturalist Vol. 47, No. 4

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