Utah State University DigitalCommons@USU All Graduate Theses and Dissertations Graduate Studies 5-1976 Insect Consumption of Seeded Rangeland Herbage in a Selected Area of Diamond Fork Canyon, Utah County, Utah Diane M. Bowers Utah State University Follow this and additional works at: https://digitalcommons.usu.edu/etd Part of the Biology Commons 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 specifi- cally 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 detri- mental impact on range was suggested by the data, as insects consumed for- age 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 cap- able 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.