Insect Consumption of Seeded Rangeland Herbage in a Selected Area of Diamond Fork Canyon, Utah County, Utah

Utah State University DigitalCommons@USU

All Graduate Theses and Dissertations Graduate Studies

5-1976

Diane M. Bowers Utah State University

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Recommended Citation Bowers, Diane M., "Insect Consumption of Seeded Rangeland Herbage in a Selected Area of Diamond Fork Canyon, Utah County, Utah" (1976). All Graduate Theses and Dissertations. 3478. https://digitalcommons.usu.edu/etd/3478

This Thesis is brought to you for free and open access by the Graduate Studies at DigitalCommons@USU. It has been accepted for inclusion in All Graduate Theses and Dissertations by an authorized administrator of DigitalCommons@USU. For more information, please contact [email protected]. INSECT CONSUMPTION OF SEEDED RANGELAND HERBAGE IN A SELECTED AREA OF DIAMOND FORK CANYON, UTAH COUNTY, UTAH by Diane M. Bowers

A thesis submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE in Biology

UTAH STATE UNIVERSITY Logan, Utah

1976 ACKNOWLEDGMENTS

would like to thank my committee for the interest shown, the guidance given, and suggestions made in relation to this study. I am also grateful for their comments in reviewing and editing the manu- script. wish to extend my sincere gratitude to Dr. B. A. Haws, who served as my major professor and to whom am grateful for his personal interest and time given to the project. would also like to thank Dr.

Clayton S. Gist and Dr. Cyrus r~. McKell for their suggestions on opera- tional procedures and comments on the rangeland aspect of this study.

I would like to extend my appreciation to the Spanish Fork

Forest Service for a 11 owing the study area to be on Sterl ing Ranch and for providing materials and manpower for the construction of the sampling enclosures.

Finally, I would like to thank Naurice Zeeman, whose cheerful attitude and enco uragement made the long hours of sample counting endurable and the hours of writing tolerable.

~ 711. ,(3=./L~ Diane M. Bowers

ii TABLE OF CONTENTS

Page

ABSTRACT INTRODUCTIO N REVIEW OF LITERATURE Utah range 1and 3 Wheatgrasses 3 Range 1and pests 4 Classification and description of the insect 4 Life cycle and behavior 5 Importance of problem 8 Control 10 STUDY AREA 12 METHODS AND PROCEDURES 13 Forage consumption treatments 13 Insecticide treatment . 13 Insect population inventories 15 Forage production . 19 Temik growth responses 20 RESULTS AND DISCUSSION . 21 Insect populations 21 Herbage production 24 Effects of forage consumption 27 CONCLUSIONS 32 APPENDICES 33 LITERATURE CITED 41

iii LIST OF TABLES

Tabl e Page

1. Forage production in the three treatment areas 26

2. Amounts of forage consumed by cattle and insects at the study site 29

iv LIST OF FIGURES

Figure Page 1. Adult black grass bugs 6

2. Discoloration of grass caused by L. hesperius 9

3. Area of discolored grass at the study site damaged by L. hesperius

4. Enclosure used for total and partial exclu sion plots 14

5. Land surrounding the enclosures comprised Area 3, the non-exclusion area 14

6. Sweeping method used for arthropod popula tion inventories 16

7. D-Vac machine used for quantification of the adult Labops population 18

8. Population trends of the four major groups of insects present at the study site in 1975 22

9. Duration of the nymphal and adult stages .of Labops hesperius at the study site in 1975

10. Average grass weights for the three treatment areas and indication of time periods of maxi mum populations of the four major insect groups at the study site 25

v ABSTRA CT

Insect Consumption of Seeded Rangeland Herbage In a Selected Area of Diamond Fo r k Canyon, Utah County, Utah

Diane M. Bowers, Master 9f Science Utah State University, 1976 Major Professor: Austin B. Haws Department: Biology

This study compares insect and cattle consumption of crested wheat grass (Agropycon spp.) on a site in Sterling Ranch, Utah County, Utah. The hypothesis tested is that insect consumption in general, and specifically consumption by Labops hesperius Uhler, significantly reduces total available cattle forage. Labops and grasshoppers were probably the major cause of secondary damage at the study site, while the impact of thrips is unknown. A detrimental impact on range was suggested by the data, as insects consumed forage equivalent to 2.8 animal units per month, while cattle consumed forage equivalent to 2.1 animal units per month at the study site. Based on a grazing fee of $1.60 per animal unit per month, this represents a loss of $3 . 50 per acre. Although a low level Labops population was present at the time of the study, potential exists for this population to reach higher level s that would cause much higher levels of damage. Crested wheatgrass, the major vegetation at the study site, is capable of resuming growth in the fall if there is sufficient moisture . Be- cause there is only one generation of Labops per year, fall herbage produc tion would not suffer Labops damage, but may suffer damage by other in sects that are present in the fall. (45 pages) vi INTRODUCTION

Grazing lands are vital to the continued economic well-being of the western livestock industry. Estimates indicate the livestock grazing capacity in the western United States had decreased by half or more in the past century. Causes of this decline include factors such as excess livestock and big-game grazing, fire, unfavorable weather, large rodent populations, plant diseases, man's agricultural activities, and insects (Hormay, 1970). The magnitude of the ill effects of insects has only recently been realized. Studies of the impact of insect populations on ran geland indicate insects may damage forage by consumption, weakening or killing plants, making forage unattractive to livestock, and/or de stroying seed (Stoddart, Smith, and Box, 1975). One insect group of recent concern is the black grass bug complex, Labops spp . and Irbisia spp. These bugs are believed to severely damage thousands of acres of range grasses annually, especially if moi st springs make abundant forage growth possible, and may render entire range seedings unfit for forage (Jensen, 1971; Kotter, 1972). Because such damage adds to the cost of raising cattle, the black grass bug is considered a major range pest. This study was formulated to test the hypothesis that insect for age consumption in general, and specifically consumption by Labops hes perius Uhler, significantly reduces total available cattle forage. The objectives of the study were: l) to determine the effects of insect con sumption, and specifically that of Labops, on available herbage, 2) to learn more about the life hi story and habits of Labops , 3) to observe the interaction of the Labops population with other insects, and 4) to provide information beneficial to range users and range management pro grams . 3 REVIEW OF LITERATURE

Utah range 1and Rangelands, as defined by Stoddart et al . (1975) are areas of ... low and erratic precipitation, rough topography, poor drainage, or cold temperatures--are unsuited to cultivation and which are a source of forage for free-ranging native and domestic animals, as well as a source of wood products, water, and wildlife. {p. 2) Eighty-nine per cent of Utah, approximately 19,000,000 ha, may be class ified as rangeland (Nielsen, 1967). The intermountain region, in which Utah is located, has an arid climate with dry summers and an average annual precipitation of 350 mm (Keller and Klebesadel, 1973). According to Keller and Klebesadel {1973), "The predominance of non-cropland in the area emphasizes grazing and a livestock-oriented economy." {p. 486)

Wheat grasses Wheatgrasses (tribe Hordeae, genus Agropyron ) are important in western rangelands as they provide early season forage of high nutrition al value (Rogler, 1973) . Of this group, crested wheatgrasses are the most commonly used introduced grasses for range seedings in the western United States (Currie, 1970). Two members of the crested wheatgrass complex, A. aristatum and A. desertorum, were the predominant grasses seeded on the study site . Native to eastern Russia, western Siberia, and central Asia, these two grasses are hardy, drought resistant, perre nial bunch grasses (Rogler, 1973) . Like other members of the genus, they reacr maximum development in late spring or early summer, are semidormant in hot weather , and can resume growth in the fall if precipitation and temperature are favorable. For these reasons, they are classified as cool season grasses (Odum, 1971) . 4 Rangeland pests Pocket gophers (Thomomys spp.) were the rodents of major concern at the study area. Presently, much controversy exists as to the status of this rodent as a pest of range areas (Stoddart et al . , 1975). Some researchers, such as Julander, Low, and Morris {1969), believe pocket gop hers are detrimental to range in a variety of ways, while others, such as Ellison (1946), and Ellison and Aldous (1952) believe the rodents to be beneficial, or at least not primarily responsible for range deteriora tions such as erosion. Turner (1973), Branson and Payne (1958), and Humphrey (1962) believe pocket gopher activity to be both beneficial and detrimental . Apparently , the effects of this rodent vary with location, vegetation, size of gopher population, season, and interaction with other animals in the area (Turner, 1973) . According to Knowlton {1954), insects attack and damage almost all important range food plants . Insects may detrimentally affect vegetation by consuming forage, weakening or killing plants, making forage unattrac t i ve to animals, or destroying seed (Stoddart . et al . , 1975) .

Classification and description of the insect Labops hesperius Uhler (Hemiptera, Miridae) was the primary object of thi s study. As with other bugs of the genus Labops , it is commonly referred to as a black grass bug, or wheatgrass bug. A homogeneous group, Labops is distinct from related Nearctic genera in the subfamily Orthoty oinae. Holarctic in distribution, the genus is principally found in northeastern North America and northeastern Siberia. One species extends into eastern North America and eastern Europe (Slater, 1954). Uhler (1872) initiated detailed taxonomic work with Labops , using specimens collected in Colorado and Montana during the Hayden expedition. Knight (1922) formulated a key to the North American species of Labops . A more extensive key, including descriptions of three new species of Labops , was compiled by Slater (1954) . Adult Labops , approximately 0.64 em in length, are opaque black with buff colored wing margins and are distinguished by the bluntly tri angular and vertical head, which bears strongly pedunculate eyes extend ing laterally beyond the margins of the pronotum. The slender condition of the third and fourth antennal segments and the strongly dimorphic hemelytral development are also distinguishing characters . Figure 1 shows the three species of Labops that are found in Utah in substantial numbers: L. heaperius, L. hirtus, and L. utahensis (Haws , Dwyer, and Anderson, 1973) . The latter is more elongate and of greater average length than L. hesperius and L. hirtus. Apparently the predomi nant species in Utah is L. hesperius, especially at elevations of 1830 - 2740 m. It can be recognized by the black legs, grayish prostrate pubes cence on the scutellum and the hemelytra, and yellowish markings on the face and co xae . Labops hirtus is easily distinguished by the long hairs on the hemelytra.

Life cycle and behavior Although the complete life cycles of all species of Labops are not known, studies of L. hesperius indicate that there are five nymphal in stars before the adult stage (Haws et al., 1973; Kamm, 1974; Todd and Kamm, 1974) . There is only one generation per year with the insects over wintering as eggs for a period of approximately nine and a half months Figure 1. Adult black grass bugs Top: Labops hesperius , the object of the study Middle: Labops hirtus Bottom: Labops utahensis (Brandt, 1966; Todd, 1974) . The stimulus for location of the oviposition site is unknown. Labops eggs , which must be exposed to cold winter temp eratures for completion of embryonic development, occur in both green and dry brown grass stems as well as in non-grass plants (Haws et al . , 1973; Kamm, 1974).

Labops eggs hatch in spring after snow melt; the exact time is probably correlated with temperature (Lindsay, 1970; Kamm, 1974). Obser vations by Brandt (1966) and Todd (1974) indicate that each stadium lasts approximately one week. Mating occurs approximately two weeks after the adult stage is reached. The total life span is two to two and one half months (Brandt, 1966; Todd , 1974). Although two pairs of wings are present on adults of both sexes, the ability of Labops to fly has been questioned. While males have macropterous metathoracic wings , the majority of females have vestigial metathoracic wings. Todd (1974) reported 75 % of the females he examined were brachypterous. These females are believed incapable of flight. Macropterous adults, male and female, are potentially capable of flight; Higgins (1975) and Todd (1974) observed short distance gliding and flight of 0.3 m or less . Like other hemipterans, black grass bugs have piercing-sucking mouthparts often referred to as a beak. Labops commonly feed on native and introduced grasses and have been reported on non-grass plants. In feeding, Labops pierce the plant cell wall and remove nutrients and photo synthetic material (Markgraf, 1974). This results in whitish spots ap pearing where the beak pierced the plant, thus giving it a mottled appear ance . Studies by Haws et al. (1973), revealed that Labops frequently feed with their heads pointing to the ground and move progressively from the tip to the base of the leaf. 8 Importance of problem Black grass bug damage, reported on crested wheatgrass (A. cris tatum , A. desertorum ), intermediate wheatgrass (A. intermedium), blue bunch wheatgrass (A. spicatum), pubescent wheatgrass (A. trichophorum), quackgrass (A. repens ), smooth brome (Bromus inermis), cheatgrass (B. tectorum), orchardgrass (Dactylis glomerata ), giant wildrye (Elymus cinereus ), Idaho fesque (Festuca idahoensis ), barley (Hordeum spp.), bulbous bluegrass (Poa bulbosa ), Kentucky bluegrass (P. pratensis ), and Lemmon's needlegrass (Stipa spp.), is of such severity that the situation in some areas is considered worse than any grasshopper infestation in Utah (Knowlton, 1966; Jensen , 1971; Hunsaker, 1966). Heavy infestations occur during moist spring growing seasons apparently related to abundant forage growth (Jensen, 1971), and i n pure stands of grass (Rathbun, 1969) . Black grass bug populations may need several growing seasons to reach critical levels (Gray, 1975). Investigations of Labops infestations indicate that £. hesperius comprises 95 to 99% of the black grass bug infestations on crested wheat grass on high mountain and range areas (Knowlton and Roberts, 1971) . This species is widespread ; it occurs in Arizona, California, Colorado, Idaho, Montana, Nebraska, New Mexico, Oregon, South Dakota, Utah, Washing ton, Wyoming, Alberta, British Columbia, and the Yukon Territory (Anon. l966a; Armitage, 1952). Grasses damaged by Labops infestations are easily recognized by whitish or yellowish spots on the plants (Figure 2); this feeding effect gives heavily infested fields a straw-colored appearance, as can be seen in Figure 3 (Thornley, 1967) . Leaves damaged while young become brown and dry (Knowlton, 1966; Jensen, 1971) . In addition to leaf discoloration, 9

Figure 2. Discoloration of grass caused by L. hesperius

Figure 3. Area of discol ored grass at the study site damaged by L. hesperius lU black grass bug feeding is believed to stunt or retard plant growth, de crease seed and hay yields , and reduce palatability of the grass (Anon. 1966a; Anon. 1971; Gray , 1975) . Feeding injury to grasses by Labops reduces the nutritional value . During the period of heaviest feeding (adult stage) there may be as much as a 13% reduction in herbage which is also five per cent less digestable (Ma rkgraf, 1974) . Injured plants may resume growth after a black grass bug i nfestation if there is sufficient moisture, resulting in "normal" herbage production (Gray, 1975; Knowlton, 1966; Jensen, 1971; Markgraf, 1974).

Control Prior to the use of low volume malathion sprays, DDT was used to control Labops populations with nearly 100% effectiveness (Mattson, 1967). In a spray test reported by Thornley (1967) using malathion and dibrome, malathion wa s found to be as effective as DDT, while dibrome only result ed in a 10% reduction in the Labops population. The success of a spray program designed to control Labops popula tions is at least partially dependent upon timing. The spray must be ap plied after most of the eggs hatch but before the adult stage, to ensure a low Labops population the year following the spray (Lindsay, 1970; Thornley, 1969). Spraying with 8 ounces of 95 % malathion per 0.4 ha during the nymphal stage controls the bugs for at least two years (Thomp son, 1969) . Lindsay (1970) questions the effectiveness of livestock grazing as a control of Labops populations . One report indicates heavy late fall grazing does aid in reducing black grass bug populations (Anon. 1966b) . 11

Field burning or removal of a haycrop may also be feasible methods for reducing Labops populations (Markgraf, 1974). 12

STUDY AREA

The study site was a seeded range area on the Sterling Ranch in Diamond Fork Canyon, located southeast of Spanish Fork , Utah County, Utah . Approximately 0.533 ha in size and at an elevation of 1700 m, the area contained three major vegetation types: bulbous bluegrass, a crested wheat complex, and white top (Cardaria spp . ). The bulbous bluegrass occupied the southeast corner of the study area and matured two to three weeks before the wheatgrasses, although both began growth in early spring while snow was still on the ground . There were two patches of white top, occupying a total area of approxi mately 50m2, in the northeast corner of the area . The predominant vegetation at the site was crested wheatgrass (A. cristatum); mixed with this was desert wheatgrass (A. deser torum ) at a density of two to three plants per 25 m2. A strip approximately 270m2 along the eastern boundary of the study site was predominantly desert wheatgrass . As this strip had a distinct border, it was hypothesized that the desert wheatgrass had been used to finish seeding the area when the supply of-crested wheatgrass ran out . Mammals encountered in the study area were cattle and rodents. First observed on June 21, 1975, the cattle herd contained cows, bulls, and calves. Pocket gophers were the predominant rodent on the study site, but Forest Service Pest Control personnel considered the population level to be insignificant . In comparison, areas surrounding the ranch were termed heavily infested with the rodent . 13 METHODS AND PROCEDURES

Forage consumption treatments To study the impact of insect consumption on the vegetation, three types of areas were used : Area 1: Total exclusion of insects, rodents, and grazing animals, Area 2: Insects allowed to feed, but rodents and grazing animals excluded, Area 3: Livestock, wildlife, wildfire, and insects permitted a normal field existence. Areas 1 and 2 each contained five enclosures and were constructed by the U.S. Forest Service in December, 1974, after random selection of the plot locations. Each enclosure (Figure 4), built of wire field fence and metal flashing, was 25m2 wide and 1.5 m high . The land surrounding the enclosures comprised Area 3 (Figure 5).

Insecticide treatment To exclude arthropods from Area 1, Temi k, a granular systemic in secticide approved by the Spanish Fork District of the U.S. Forest Service, was applied April 19, 1975 at a rate of 187.5 g/25 m2 (75 lb/a). At the time of application, snow melt and heavy run-off were completed, but ground moisture was sufficient for activation of the toxicant. Use of a spreader was not feasible due to the small quantity of Temik involved and gusty spring winds, therefore the insecticide was applied by a shaker. This device, a plastic bag filled with the measured amount of Temik, was punched with holes and then shaken over the area to evenly distribute the insecticide. To aid in leaching of the toxicant into the root zone, each treated area was raked . 14

Figure 4. Enclosure used for total and partial exclusion plots.

Figure 5. Land surrounding the enclosures comprised Area 3, the non-exclusion area. 15 In sect populati on inventories Insect population samples were obtained by sweeping with a stand ard 0.38 m diameter beating net (Figure 6). Twenty sweep samples were taken every week from May 4 through August 25, 1975, during each of two time periods: 0830 - 0930 and 1100 - 12QQ M.D.T. All samples were in a randomly chosen location in the area surrounding the enclosures, each sweep sample consisted of twenty strokes back and forth with the net in a manner similar to the pendulum method described by Ambrust, Niemczyk, and Wilson (1932) . Many researchers (Blickenstaff and Huggans, 1969; Cothran and Summers, 1972; Delong, 1932 ; Gray and Treloar, 1933; Lockwood, 1924; Saugstad, Bram, and Nyquist, 1967; Turnbull and Nichols, 1966) are of the opinion that the sweep method does not yield accurate data for criti cal population comparisons because it is influenced by factors such as temperature, sun position, wind velocity, and plant size and condition (Delong, 1932). On the other hand, the sweep method does provide an easy estimation of population trends (Beall, 1935; Callahan, Holbrook, and Shaw, 1966; Hughes, 1955; Saugstad et al., 1967). Some population sampl ing methods preferred to sweeping are the sequential stem analysis, the pan method, and a suction apparatus. According to Cothran and Summers (1972) a combination of methods may be necessary to sample different life cycle stages. There were two major reasons for choosing the sweep method over other population sampling procedures as the primary method in this study .

First, advice received from two other Labops researchers (Kurt Higgins and Alan Gray, 1975) revealed that the more consistant and accurate suction method (Johnson, Southwood, and Entwistle, 1957) was so damaging 16

Figure 6. Sweeping method used for arthropod population inventories. 17 to the small and fragile early instars of Labops that the sample counts were not always accurate. Secondly, use of sampling apparatus that could not be easily carried, or required more than one person to operate, would commonly yield inaccurate results as the quick moving black grass bugs are extremely sensitive to disturbance and sound (Gray, 1975; Thornley, 1967). Also, supporting the opinion of Fenton and Howell (1957) that the sweep method is good for locating extremely light infestations, Rathbun (1969) discovered that the sweep method caught bugs in areas where they previously were not detected. Quantification of the adult population was achieved by sampling with a D-Vac, a suction apparatus (Figure 7). Preliminary D-Vac sampling was tried in East Canyon Reservoir (Morgan County) and in the vicinity of the Tony Grove Forestry Station (Cache County) in June, 1974. A sampling ring (1.0 m2) of 0.5 em sheet metal, 20 em deep, with a beveled edge, was positioned in the area to be sampled. The ring provided a constant area to be D-Vacked and prevented movement of Labops in and out of the sampling area. This method necessitated D-Vacking, clipping all standing grass in the area, and again D-Vacking to collect all insects within the ring. The above method was not feasible for this study. Moving the ring and positioning the D-Vac disturbed insects, causing them to move to other areas. Highly mobile insects, such as grasshoppers, easily escap- ed while the ring was being positioned. Such insect movement could have resulted in collecting higher or lower numbers of insects in an area than would be otherwise present. To reduce these problems, the method employed used the funnel of the D-Vac (0.03 m2) as the sampling area. This eliminated the disturbance 18

Figure 7. D-Vac machine used for quantification of the adult Labops population. 19 caused by the metal sampling ring. It also lessened the disturbance caused by the D-Vac as the machine had only to be moved once for each sample. The length of the hose connecting the funnel to the D-Vac allowed sampli ng away from the immediate area disturbed by the machine. Using this method, the D-Vac only had to be employed once for each sample as insects in the area sampled were immediately sucked up and did not have a chance to hide in the litter. Twenty random samples, each covering an D.D3 m2 area, were taken on each of six sampling periods following the sweep sampling during the period of June 22 through July 14, 1975. As previously discussed, this method was impractical for sampling Labops nymphs. Both D-Vac and sweep samples were kept in paper ba gs until they could be examined macro- and microscopically. As a potential existed for insect body breakage with both methods, each insect head found was counted as one insect, regardless of whether a body was attached or not. As heads tended to break cleanly from the body and remain intact, this method allowed quick and accurate counting of samples.

Forage production Analysis of vegetation dry weights indicated forage production. The samples were obtained on alternate weeks for the duration of the grass growing season. Herbage was clipped at ground level in randomly chosen 0. 11 m2 areas. A total of twenty clipped samples was taken from Areas 1 and 2, and ten were obtained from Area 3 during each sample period. Kept in paper bags, the samples were allowed to dry and were then weighed. Area 1 was assumed to produce the maximum average herbage for the season. Subtracting average forage weights in Area 2 from those 20 of Area 1 indicated the amount eaten by insects . Similar manipulation with Area 3 data indicated the amounts consumed by cattle.

Temik growth responses If Temik (C H N metabolized to a form making nitrogen 7 14 2o2s) available to the crested wheatgrass in Area 1, it presumably would stimulate plant growth and increase yields. Such an effect would re sult in erroneous maximum herbage production data. To determine whether Temik had any stimulatory effects on crested wheatgrass, a greenhouse study was conducted. Two hundred crested wheatgrass plants were grown in ten flats. Five flats were treated with Temik at a rate of 7.5 g/m2 (75 lb/a); the remaining five flats were retained as controls. The flats, set up in two rows , alternated Temik and non-Temik flats in checker board fashion. 21 RESULTS AND DI SCUS SION

Insect populations Black grass bugs, grasshoppers (Acrididae), leafhoppers (Cicadel lidae), and thrips (Thysanoptera) were the four groups comprisi~g the majority of insects caught. Accounting for less than nine per cent of the insects caught were Lepidoptera, Coleoptera, Diptera, Homoptera, Hymenoptera, Thysanura, and Hemiptera other than Labops. Thrips were first observed on May 17 . The population peaked June 14 and declined August 18. Leafhoppers, first collected on May 4, at tained a maximum population on June 14. After declining sharply, the population fluctuated between 35 - 100 per sweep throughout the remain der of the sampling period. Grasshoppers were not observed until May 31. In the following month the population increased, peaking on July 14. The population then gradually declined through the end of the sampli ng period. Figure 8 illustrates the various population trends. Black grass bugs were first collected on May 5. At the time the majority of the bugs were second instars, and a small percentage were third instars. Other studies indicate the first stadium is a maximum of one week, therefore the bugs at the study site probably hatched on April 26 or shortly t he reafter (Higgins, 1975 ; Todd, 1974) . The third, fourth, and fifth stadia each lasted approximately one week. Studies in New Mexico, southern Ut ah, and Oregon indicate the same duration for these stadia (Brandt, 1966; Higgins, 1975; Todd, 1974). By May 31 the majority of the bugs were adults. They were first observed mating on June 7, the second week of adulthood (Figure 9). Brandt (1966), Kamm (1974), and Todd (1974) also report mating occuring the second week of 22

4000

1000 r\ -\ • \;\/ "\_ • \ • thri ps

"'c. "' "'~ 100 0 N -;;:,-..., I u ~ c: ! ;, leafhoppers "'" ' \ "''- .....-\ . > I <"' 10 - _./ ""- grasshoppers

+~lay+ +J une+ +J ul y+ SAPlPLE DATES

Figure 8. Populati on trend s of the four major aroups of insects ~re s ent at the study s ite i n 1975. Adult

Fifth ins tar -- Fourth • - observed i nstar .. - calculated, based on population observa - tion and an average duration of 1 week Third _____.. per instar ins tar ~ - mating Second ..,.___. • - zero population i nstar I I I - maximum population level First ...... ins tar

26 5 10 17 24 31 7 14 14 Apri 1+\ + May -+- \+ June ... I... July Figure 9. Duration of the nymphal and adult stages of Labops hesperius at the study site in 1975 .

t3 adulthood . The Labops population rapidly declined after reaching a maxi mum between May 31 and June 22 of approximately 200 per sweep (Figure 8). 0-Vac data indicated a maximum population of at least l ,900,000 Labops / 0.52 ha . By July 14 the population had decreased to a near zero level ; therefore development and reproduction were completed in less than three months . Compared with other Labops investigations, the Labops population level was low. At Blackett's Pasture, a few miles northeast of the study site, 900 Labops per sweep were collected (Haws, 1976); Thornley (1967) reported 1,000 Labops per square foot at Ka nab Creek. In both these areas plants were severely damaged and produced little or no seed.

Herbage production Average grass weights for each of the treatment areas are shown in Figure 10 . Major differences in average grass weights occurred after June 14. On each sampling day thereafter Areal, the total exclusion area, produced a greater average amount of herbage than Areas 2 or 3, primarily insect consumers, and non-exclusion areas, respectively. The maximum average herbage weights per 0. 11 m2 (1.2 ft2) for Areas l, 2, and 3, respectively, were : 57 .1 g on August ll, 41. 7 g on July 14, and 31 .5 g on June 28 (Table 1) . The decrease in grass weights on August 25 for all three areas probably reflects the end of the growing season. Such high production in the control plots may have been caused by the absence of nematodes as well as insects due to the effects of Temik (Union Car bide Corporation, 1975). The maximum average herbage production data were compared with data on grassland energetics obtained by Andrews, Coleman, Ellis. • and 25

+A-+ 40 ~ /- ( \ Area 2 ~ insect consumers 'I/,.._ ___ _ 30 t/ ...... I '~---'-"' +-> ~ ' ·a;Ol ·' ' ): ' ' .. ::: 20 Area 3 ...0 cattle and insect Ol consumer!s "'Ol "'... ~"' 10 A - period of maximum Labops population B - period of maximum leafhopper population C - period of maximum thrips and grasshopper population

14 28 +May-+ +June-+ +July-+ +August ... SAMPLING DATES Figure 10 . Average grass weights for the three treatment areas and indi cation of time periods of maximum populations of the four major insect groups at the study site .. L6

Table 1. Forage production in the three treatment areas.

Average grass2weights per 0.11 m (g) Date (1975} Area 1 Area 2 Area 3 Total exclusion of Exc lusion of insects, cattle, cattle Non-exc 1 us ion and rodents and rodents

5/17 13.4 11 .3 12 .2 5/31 17 .4 15.65 15.48

6/14 18.74 18.62 23.99

6/28 49.35 38.14 31.48 7/14 45.58 41.73 29.66 7/28 45.81 33.70 26.27 8/11 57.11 37.92 27.85 '

8/25 53.91 37.03 21.96 27 Singh {1974) at the Pawnee Site in Colorado by using a conversion factor of 4. 6 kcal/g. Production in Area 1, the control area in this study, was greater than production in the ungrazed area at Pawnee, while pro duction in Areas 2 and 3 was at an intermediate level between the Pawnee lightly grazed and heavily grazed areas. These differences may be due to the differences between the two grasses at the two sites (blue grama [BouteZoua gracilis], a warm season grass, was the predominant vegeta tion at Pawnee) and the moist spring growing season favoring growth at Sterling Ranch in 1975. Comparison supports the field observations. An analysis of variance showed significant differences at the 5% level of probability between treatments, time, and the treatment-time interaction. These results indicated significant differences in forage production between the three treatment areas, over the period of time of the study (actually indicating significant growth in each of the three areas), and between the study areas through the duration of the study. An analysis of variance of the data from the greenhouse study showed no significant difference at the 5% level of probability between the dry weights of crested wheatgrass treated with and without Temik. These re sults implied Temik did not metabolize to a product making nitrogen available to crested wheatgrass and indicated Temik did not stimulate crested wheatgrass growth and yield. Therefore, production differences between the field treatment areas were assumed to be primarily due to animal consumption. This assumes other factors affecting plant growth to be the same throughout the study area or negated by random sampling .

Effects of forage consumption Analysis of the average grass weights for each week indicated the total possible forage available and cumulative amounts consumed by in- 28 sects and cattle (Table 2) . Inconsistencies in the data occurred on June 14 and July 14. These were probably due to the small sample size used; a larger sample size would have been possible if the enclosures had been larger. Comparison of herbage production in Areas 1 and 2 indicated direct and indirect effects of insect consumption (Figure 9). Major pro duction differences of 10 g/0.11 m2 did not occur until June 28. Before that date average sample weights did not differ by more than 3 g/0.11 2 m . This decrease may be attributed to grasshoppers and thrips, as the populations were at peak levels at the time. Whether thrips had a sig nificant role in the effect is unknown. Bailey {1938) and Hewitt et al. (1974) believe thrips damage to be minimal and of little economic impor tance, while Tingey, Jorgensen, and Frischknecht (1972) found that high populations of some species of thrips may cause considerable damage to crested wheatgrass. That grasshoppers would be responsible for reduced forage production was anticipated as they may remove as much as 43% of available forage (Stoddart, et al . , 1975). In his study of Labops , Gray (1975) also suspected grasshoppers were responsible for a drop in forage production . The data (Figure 10) indicated no direct effect on forage production due to Labops as there was no major difference in production levels between Areas 1 and 2 when the Labops population reached its ma ximum . Yellowing of the grass due to Labops feeding did occur {Figures 2 and 3) . Sequential insect l i fe cycles prevented determination of indirect consumption effects by any particular group . Large Labops populations may cause stunting of plants due to feeding removal of cell contents, in- eluding photosynthetic material (Gray, 1975; Markgraf, 1974). Visual ob- 29

Table 2. Amounts of forage consumed by cattle and insects at the study site

Amounts of forage co nsumed Amounts forage consumed by insects by cattle Date 1975 g % of total g % of total

5/17 2.1 15. 67 5/31 1. 75 10.06 6/14 0.12 0.64 6/28 11.21 22.72 6.66 13 .49 7/ 14 3.85 8.44 12.07 26.48 7/28 12 . 11 26.44 7.43 16 .21 8!11 19.19 33.60 10.07 17.63 8/25 16. 88 31 . 31 15.07 27.95 30 servations indicated plants in Area 1, total exclusion, were taller than those in Areas 2 and 3, primarily insect consumers and insect and cattle consumers respectively; this may be attributed in part to Labops. The extent of such a secondary effect, if it occurred, could not be determin- ed from the data, due to the large number of grasshoppers present after the black grass bugs died in mid-July. Potential plant recovery (Gray, 1975; Mills, 1941) from secondary Labops damage was indeterminable for the same reason. Recovery from the effects of forage consumption by cattle and insects did not occur as production in Areas 2 and 3 never attained the levels of Area 1. These results also indicated insects reduced primary production . Analysis of the data showed that cattle ate a total of 26 - 28% of the total available herbage, while insects consumed a total of 31 - 34 %. Thus, if insects had been controlled, approximately twice as many cattle could have been on the area. The animal units per month (AUM's) lost due to insect consumption were calculated based on the size of the area infested, the maximum consumption per unit area by insects, and the AUM equivalent. Respectively, these were: 5,200 m2 (1.3 a) infested, 19.19 g/m2 (0.014 lb/1.2 ft2) maximum cons umed by insects, and 327,200 g/AUM (720 lb/AUM) (Stoddart et al., 1975). Similar ca l cu l ations were done for cattle consumption. It was not possible from the data to account for the reserve plant material eaten by insects that would not be eaten by cattle. The results showed forage equivalent to 2.8 AUM was consumed by the insects, and forage equivalent to 2.1 AUM was consumed by the cattle at the study site. These results can be used to determine the economic impact of insects on rangeland. In 1971, 5,000 acres of reseeded rangeland in the 31 Dixie National Forest were se verely damaged by Labops (Jensen, 1971 ). Using insect forage consumption equivalent to 2.8 AUM/0.52 ha and a grazing fee of $1.60/AUM, thi s represented a loss of approximately $17,600. 3L

CONCLUSION S

Development and reproduction of Labops hesperius at the study site lasted approximately three months, with each of the nymphal stadia lasting approximately one week. Mating occurred the second week of adult hood . These observations concur with those of Brandt (1966), Higgins (19 75), and Todd (1974) . Spray ing to control Labops populations sho uld be used after eggs hatch and before the adult stage. This method will control the population before the egg laying stage, thereby ensuring a low population level the following year. Lack of grass recovery at the end of the growing season indicated indirect insect damage . Labops and grasshoppers were probably the major cause of secondary damage at the study site, while the impact of thrips is unknown . A detrimental impact on range was suggested by the data as insects consumed forage equivalent to 2.8 animal units per month while cattle consumed forage equivalent to 2.1 animal units per month at the study site. Based on a grazing fee of $1.60 per animal unit per month, this represented a loss of $3 .50 per acre. Although a low level Labops population wa s present at the time of the study, potential exists for this population to reach higher levels that would cause much higher levels of damage (Gray, 1975). Crested wheatgrass i s capable of resuming growth in the fall if there is sufficient moisture. Because there is only one generation of Labops per year with the bugs dead by August, fall herbage production would not suffer Labops damage, but may suffer damage by other insect groups that are present in the fall. 33

APPENDICES 34 Appendix A

Total numbers of insects caught by the sweep method

Number Date of Labops Grasshoppers Leafhoppers Th rips Others (1975) sweeps

5/4 18 200 0 0 ll

5/10 20 10 0 0 4

5/ll 20 137 0 0 8

5/17 20 644 0 ll 6 55

5/18 20 1679 0 0 0 14

5/31 20 1530 0 4 4 28

6/l 20 4868 ll 100 13

6/7 20 1882 4 37 217 57

6/8 20 3208 4 26 44 50

6/14 20 4122 17 181 1066 178

6/15 20 4145 19 491 646 183

6/22 20 3292 15 63 511 170

6/28 20 719 21 54 1014 1 3~

6/29 20 276 24 70 748 132 35 AEEe ndi x A, continued

Number Date of Labops Gras shoppers Leafhoppers Thrips Ot hers (1975) sweeps

7/5 20 12 16 37 1120 226

7/6 20 25 35 37 856 123

7/14 20 55 62 1183 242

7/ 15 20 0 33 59 799 144

7/21 20 13 55 416 87

7/21 20 15 52 457 156

7/28 20 0 14 136 1076 253

7/29 20 0 15 68 395 98

8/4 20 0 9 71 353 152

8/4 20 27 75 526 246

8/11 20 8 71 575 206

8/11 20 0 16 76 925 42 1

8/18 20 17 65 548 267

8/18 20 0 13 80 459 216

8/25 20 0 12 34 26 1 58

8/25 20 0 9 50 371 78 36

Appendix B

Total numbers of insects caught by the D- Vac method

Date Number of Labops Grasshoppers Leafhoppers Thrips Others (1975) samples

6/22 20 277 6 16 43 28

6/28 20 15 8 4 9 3 31

6/29 20 147 12 59

7/5 20 63 7 18 82

7/6 20 13 13 8 82

7/14 20 164 3 6 47 37

Appendi x C

Total dr~ weights of clipped herbage

Number Area 1 Area 2 Area 3 ·Date of Insects present; Insects, cattle samples Cont ro 1 cattle and and rodents ( 1975) oer area rodents excluded present (g) (g) (g)

5/ 17 5 63 .4 49 . 5 81.8 5/1 8 70.6 63.5 40.6 5/31 86.4 80 .5 77.8 6/1 5 87.6 76.0 77.0 6/14 91.7 79.4 127.5 6/15 95.7 106. 8 112 .4 6/28 266.8 205.5 169 .4 6/29 5 266.7 175 .9 145.4 7/14 5 206 .3 186 .4 132 .4 7/15 5 249.5 230.9 164.2 7/28 227.4 147.4 118.2 7/29 5 230 . 7 189 . 6 144 .5 8/11 5 283.8 184.6 145 .6 8/11 287.3 194.6 132.9 8/25 276.7 186.3 134.5 8/25 262.4 184.0 85. 1 38

Appendix D

Analysis of variance of forage data Degrees Source of Sum of squares Mean squares freedom

Treatment 7 '760 .11 3880.06 34.34 *

Time 28,570.61 4081.52 36.12 *

Treatment-Time 14 6,979.65 498.55 4.41 *

Plots-Time 96 10,847 .86 113.00 1.3

Error 120 10,478.02 87.17

Total 239 64,636.25

* Significant at the 5% level of probability 39

Appendix

Total grass dr;t weights in greenhouse stud,Y of Temik effects

Number of Temik treated Date sampled plants Non-treated plants (1975) plants per area (g) (g)

8/29 5 0.1102 0.1194 9/5 0. 1054 0.1353 9/12 5 0.1373 0.1468 9/19 0. 1288 0.0970 9/26 5 0.1452 0.1996 10/3 0. 2887 0. 2905 10/10 0.2649 0. 2227 10/17 5 0.3166 0.4686 10/24 5 0.4627 0.4523 10/31 0.3915 0. 3370 40 Appendi x F

Analysis of variance of greenhouse study data Degrees Source of Sum of squares Mean squares freedom

Treatment 0.0001 0.0001 0.0970 NS* Error 98 0.1404 0.0014 Total 99 0.1405

'*No significant difference at the 5% level of probability 41

LITERATURE CITED

Ambrust, E. J., H. D. Niemczyk, and M. C. Wilson . 1969. Standardized procedures adopted for cooperative Ohio Valley States alfalfa weevil research. J. Econ. Entomol. 62:250-251.

Andrews, R., D. C. Coleman, J. E. Ellis, and J. S. Singh. 1974 . Energy flow relationships in a shortgrass prairie ecosystem. In: First International Congress of Ecology . The Hague, September-9-14, 1974. pp. 22-28. Anon. l966a. U.S. Dep. Agr . Coop . Econ . Insect Rep. 16{26):623-624. 1966b. Grass bug infestation. Memo to Utah State Director from --Kenab District Manager. June 9. 1971 . Wheat grass bugs. Agrochem. Age. November. p. 20. Armitage, H. M. 1952. Current insect notes. Calif. Dep. Agr. Bull. No. 41. 183 p. Bailey, S. F. 1938. Thrips of economic importance in California . Univ . of Ca lif. College of Agr. Agr . Exp . Sta. Circ. 346. 77 p. Beall, G. 1935. Study of arthropod populations by the method of sweeping. Ecology 16:216-225 . Blickenstaff, C. C., and J. L. Huggans. 1969 . Four methods of sampling to measure populations of alfalfa weevil larvae. J. Econ . Entomol. 62:556-557.

Brandt, C. J . 1966. Administrative study of Labops hesperius. Santa Fe Nat . Forest. 6 p.

Branson, F. A., and G. F. Payne. 1958. Effects of sheep and gophers on meadows of the Bridger mountains of Montana . J. Range Manage . 11: 165-169 . Callahan, R. A., F. R. Holbrook, and F. R. Shaw. 1966. A comparison of sweeping and vacuum collecting certain insects affecting forage crops. J. Econ. Entomol. 59:478-479. Cothran, W. R., and C. G. Summers . 1972. Sampling for the Egyptian alfal fa weevil : a comment on the sweep-net method. J. Econ . Entomol . 65: 689-691 . Currie, P. 0. 1970. Influence of spring, fall, and spring-fall grazing on crested wheatgrass range . J. Range Manage . 23(2):103-108. 42 Delong, D. M. 1932. Some problems encountered in the estimation of in sect populations by the sweeping method . Entomol. Soc. Amer . Ann . 25 :13-17. Ellison, L. 1946. The pocket gopher in relation to soil erosion on mountain range . Ecology 27: 101 -11 4. Ellison, L., and C. M. Aldous. 1952. Influence of pocket gophers on vegetation and subalpine grasslands in central Utah. Ecology 33: 177-1 86 . Fenton, F. A., and D. E. Howell. 1957 . A comparison of five methods of sampling alfalfa fields for arthropod populations. Ann. Entomol. Soc. Amer. 50:606-611. Gray, A. M. 1975. Nutritional quality and herbage production of inter mediate wheatgrass (Agropyron intermedium [Host] Beauv.) when in fested with black grass bugs (La.bops hesperius Uhler). Unpublished MS thesis. Utah State Univ., Loga n, Utah. 42 p. Gray, H. E., and A. E. Treloar. 1933. On the enumeration of insect popu lations by the method of net collection. Ecology 14:356-367. Haws, B. A. 1976 . Labops infestation at Blackett's Pasture, Uta h County, Utah. Personal interview. Haws, B. A., D. D. Dwyer, and M. G. Anderson. 1973. Problems with range grasses? Look for black grass bugs! Utah Sci. 34(1) :3-9. Hewitt, C. G., E. W. Huddleston, R. J. Lavigne, D. N. Ueckert, D. N. Watts, and J. Gordon. 1974. Rangeland Entomol. Soc. Range Manag . Denver, Colo . Range Sci. Ser., No. 2. February. p. 52- 55 . Higgins, K. M. 1975. The effects of the black grass bug (Labope hesper ius Uhler) on several native and introduced grasses . Unpublished MS thesis. Utah State Univ. , Logan, Utah . 81 p. Hormay, A. L. 1970. Principles of rest-rotation grazing and multiple use land management. U.S. Dep. Agr . Forest Service. TT-4, 2000. September. 26 p. Hughe s, R. D. 1955. The influence of prevailing weather on the numbers of Mer omy za variegata Meigen (Diptera, Chloropidae) caught with a sweepnet. J. Anim. Ecol. 24:324-325. Humphrey, R. R. 1962. Range Ecology . The Ronald Press Company, New York. pp . 123-124. Hunsaker, L. R. , and G. F. Knowlton . 1966. Black grass bugs . Letter to all agents . Utah State Univ . Ext. Service. June 7. 43 Jensen, F. 1971 . Reseeding and Labops . Range Improvement Notes. U.S. Forest Service. Intermoun. Reg. Ogden, Utah. 16(1) :7-9. Johnson, C. G., T. R. E. Southwood, and H. M. Entwistle. 1957 . A new method of extracting arthropods and molluscs from grassland and herbage with a suction apparatus. Bull. Entomol. Res. 48:211-218. Julander, 0., J. B. Low, and 0. W. Morris . 1969. Pocket gophers on seeded Utah mountain range. J. Range Manage. 22:325-329. Kamm, J. A. 1974. Labops , a plant bug, on Oregon rangeland. Ext. Ser vice, Oregon State Univ. FS 211. 2 p. Keller, W., and L. J. Klebesadel. 1973. Hay, pasture, and range seedings for the intermountain area and Alaska. In: Forages. Heath, M. E., D. S. Metcalf, and R. E. Barnes, ed. The-Iowa State Univ . Press. Ames, Iowa. pp. 486-498. Knight, H. H. 1922. The North American species of Labops. Canadian Entomol . 54:258-261. Knowlton, G. G. 1954. Range Entomology. Mimeograph Sheet 391. Utah State Agr. College. Utah Agr. Exp. Sta . Logan, Utah. November. 3 p. Know lton, G. F. 1966. Black grass bug observations in Utah . Cooperative economic insect report. U.S. Dep. Agr. Agr. Res. Service. Plant Protec. Civ. 16( 25) :596. Kotter, C. 1972. Utah's "most wanted" insect and mite pests. The Range Guide. Ext . Service . Utah State Univ. U.S. Dep. Agr. Coop. December 18. 7 p. Lindsay, H. G. 1970. A serious threat: black grass bugs. Utah Farmer . August 6. 12 p. Lockwood, S. 1924. Estimating the abundance of, and damage by grass hoppers. J. Eco.n. Entomol. 17:197-202. Markgraf, P. M. 1974. Effect of wheatgrass bug infestation on range grasses. Abstr. papers presented 27th annual meeting, Soc. Range Manage. February 3-8, 1974. 31 p. Mattson, H. 1967. Spraying for black grass bugs. Letter to G. F. Knowl ton, Extension Entomologist. Utah State Univ., Logan, Utah. July 19. Mi 11 s, H. B. l g39. Montana insect pests, 1939 and 1940. Mont. Agr. Exp . Sta . Bull. No. 384. p. 14-18. Nielsen, D. 8. 1967. Economics of range improvements. Utah Agr. Exp. Sta. Bul. 466. 44 Odum, E. P. 1971. Fundamentals of ecology. W. B. Saunders Company. Philadelphia, Penn. p. 388-389. Rathbun, J. F. 1969. Labops spp. detection survey. U.S. Dep . Agr. Forest Service. Dixie Nat. Forest. Powell Ranger District. Re ply to: 5220 Insect and Disease Control. June 23. Rogler, G. A. 1973. The wheatgrasses. In: Forages. Heath, M. E., D. S. Metcalf, and R. E. Barnes, ed. The Iowa State Univ. Press . Ames, Iowa. pp. 221-230. Saugstad, E. S. , R. A. Bram, and W. E. Nyquist. 1967. Factors i nfl uenc ing sweep-net sampling of alfalfa. J . Econ. Entomol. 60:421-426. Slater, J. A. 1954. Notes on the genus Labops Burmeister in North America . Bull. Brooklyn Entomol. Soc. 49(3) :57-65; 49(4) :89-94. Stoddart, L. A., A. D. Smith, and T. W. Box. 1975. Range management. McGraw-Hi l l Book Company. New York. 532 p. Thornley, H. F. 1967. The grass bug Labops hesperius Uhler . Plant Con trol Division, ARS. Letter to J. R. Dutton. December 13. Thornley, H. F. 1969. Letter to R. Thompson. June 19 . Tingey, W. M., C. D. Jorgensen, and N. C. Frischnecht. 1972 . Thrips of the sagebrush-grass range community in west-central Utah. J . Range Manage. 25:304- 308. Todd, J . G. 1974. Labops hesperius Uhler: biology and impact in Oregon rangel ands (Hemiptera: Miridae). Unpublished MS thesis. Oregon State Univ., Corvallis, Oregon. 74 p. Todd, J. G., and .J . A. Kanm. 1974. Biology and impact of a grass bug Labops hesperius Uhler in Oregon rangeland. J. Range Manage. 27(6): 453-458. Turnbull, A. L., and C. F. Nichols. 1966. A "quick trap" for area samp ling of arthropods in grassland communities. J. Econ. Entomol. 59: llOO-ll 04. Turner, G. T. 1973. Effects of pocket gophers on the range. In: Pocket gophers and Colorado mountain rangeland. Colo. Agr. Exp.-sta . Bull. 554 s. p. 51-61. Uhler, P. R. 1872. Notices of the Hemiptera of the western territories of the United States, chiefly from the surveys of Dr . F. B. Hayden . .!!:!_: F. V. Hayden. 1872. Pre l iminary report of the U.S. geological survey of Montana and portions of adjacent territories, being a fifth annua l report of progress . U.S. Govern. Print. Office . Washington, D. C. p. 392-423. 45 Union Carb , de Corporation . 1975. Temik aldicarb pesticide. Salinas, Ca lifornia. 63 p.