The Effect of Insect Damage on Indian Ricegrass (Oryzopsis Hymenoides) in Western Utah

Brigham Young University BYU ScholarsArchive

Theses and Dissertations

1972-12-22

The effect of insect damage on Indian ricegrass (Oryzopsis hymenoides) in western Utah

Luis S. Guerra Brigham Young University - Provo

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BYU ScholarsArchive Citation Guerra, Luis S., "The effect of insect damage on Indian ricegrass (Oryzopsis hymenoides) in western Utah" (1972). Theses and Dissertations. 7938. https://scholarsarchive.byu.edu/etd/7938

This Thesis is brought to you for free and open access by BYU ScholarsArchive. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. THE EFFECT OF INSECT DAMAGEON INDIAN RICEGRASS (ORYZOPSIS HYMENOIDES)IN WESTERNUTAH

A Thesis Presented to the Department of Zoology Brigham Young University

In Partial Fulfillment of the Requirements for the Degree Master of Science

by Luis Guerra s. April 1973 This thesis, by Luis Guerra s., is accepted in its present form by the Department of Zoology of Brigham Young University as satisfying the thesis requirement for the degree of Master of Science.

(5? l)�e, I q 7 2.. Date

Typed by Sharon Bird

ii ACKNOWLEDGMENTS

I wish to express my sincere appreciation to my major professor and committee chairman, Dr. Stephen L. Wood, for his patience and helpful suggestions during my graduate program and the preparation of this manuscript. Appreciation is also extended to the other members of my advisory committee. I am especially indebted to Dr. Joseph R. Murdock of the Botany and Range Science Department, who suggested the problem and area of research, and to Dr. Wilmer Tanner of the Zoology Department for their time and assistance. I would also like to thank Mr. Ralph Holmgren of the Desert Experimental Range of the Intermountain Forest and Range Experiment Station of the Forest Service of the United States Department of Agriculture, for his valuable assistance and suggestions in the course of this research. And finally I wish to express my appreciation to my wife Dina for typing rough drafts, being patient and providing much encouragement and help needed to complete this research.

iii TABLE OF CONTENTS

Page

ACKNOWLEDGMENTS• • • • • • • • • • • • • • • • • • •• iii LIST OF TABLES. • • • • • • • • • • • • • • • • • • • • V LIST OF GRAPHS. • • • • • • • • • • • • • • • • • • • • vi LIST OF ILLUSTRATIONS • • • • • • • • • • • • • • • • • vii INTRODUCTION• • • • • • • • • • • • • • • • • • • • • • 1 REVIEW OF LITERATURE • • • • • • • • • • • • • • • • • • 3

METHODSAND PROCEDURES• • • • • ••• • • • • • • • • • 4 RESULTS • • • • • • • • • • • • • • • • • • • • • • • • 7

DISCUSSION • • • • • • • • • • • • • • • • • • • • • • • 25

CONCLUSIONSAND SUMMARY• • • • • • • • • • • • • • • • 32 LITERATURE CITED. • • • • • • • • • • • • • • • • • • • 34

iv LIST OF TABLES

Table Page 1. Number of Indian Ricegrass Plants Arranged by Basal Diameter Size Categories for Ea£h Study Area, Shoving Range (r), Mean (x) and Standard Deviation (SD) per 20 rn2 • • • • • • 9 2. Number of Indian Ricegrass Stems from Unin- fested Plants Arranged by Basal Diameter Size Categories fQr Each Study Area Showing Range (r), Mean (x) and Standard Deviation (SD) for the Previous and Current Growing Seasons ••••••••••••••••• • • 10 3. Number of Indian Ricegrass Stems from Infested Plants Arranged by Basal Diameter Size Categories for Eash Study Area Showing Range (r), Mean (x) and Standard Deviation (SD) for the Previous and Current Growing Seasons • • • • • • • • • • • • • • • • • • • 11 4. Number of Indian Ricegrass Plants at Warm Cove, Arranged by Basal Diameter Size Categories for Uninfested and Infested Plants Showing the Mean Number of Plants per Plot (20 m2), the Mean Number of New Stems per Plant. and the Estimated Total Number of New Stems per Plot (20. m)2 ••••••••••••••• 12 5. Number of Indian Ricegrass Plants at Overflow, Arranged by Basal Diameter Size Categories for Uninfested and Infested Plants Showing the Mean Number of Plants per Plot (20 m2), the Mean Number of New Stems per Plant. and the Estimated Total Number of New Stems per Plot (20 m2) ••••••••••••••• 13

V LIST OF GRAPHS

Graph Page

1. Percentage of Plants Damaged by Typoceris ceraticornis, Diatraea sp. and Coenchroa illibella in Each of Four Classes Arranged by Basal Diameter of Indian Ricegrass Plants in Warm Cove, Overflow and Pine Valley • • • • • • • • • • • • • • • • • • • • 14 2. Average Number of !YP9ceris ceraticomis in Each of Four Classes Arranged by Basal Diameter of Indian Ricegrass Plants in Warm Cove and Overflow •••••••• • • • • 15

vi LIST OF ILLUSTRATIONS

Figure Page 1. Pupae and Adults of Tn>9ceris ceraticornis Linsely and Chemsek •••••••••• • • • 16 2. General View of Warm Cove, Desert Range Experiment Station, 47 Miles West of Milford, Utah, August 1972 •••••••••••••• 17 3. General View of Overflow, Desert Range Experi- ment Station, 47 Miles West of Milford, Utah, August 1972 ••••••••••••••••• 18 4. General View of Pine Valley, Desert Range Experiment Station, 47 Miles West of Milford, Utah, August 1972 •••••••••••••• 19 s. An Indian Ricegrass Plant Infested by Typoceris ceraticornis, Showing the Lack of New stems, August 1972 ••••••••••••••••• 20 6. (A) Coenchroa illibella Larva and Cocoon, (B) Damaged Indian Ricegrass Plant •••• • • • 21 7. Diatraea sp. Feeding on Roots of Indian R1cegrass Plants ••••••••••• • • • • 22 a. Larvae of Typoceris ceraticornis and General Area on the Indian Ricegrass Plant Where Damage Occurs •••••••••••••• • • 23 9. Pupa of Typoceris ceraticornis in Pupal Cell at the Base of Indian Ricegrass Plant •• • • 24

vii INTRODUCTION

Indian ricegrass [Oryzopsis hymenoides (Roen & Shult) Ricker] is a bunch grass that grows 25 to 50 cm tall on arid and semiarid sites in the western United States. It is an important and abundant forage grass on the valley and foothill areas of southwestern Utah. It constitutes a significant part of many plant communities and is an important forage species for domestic and wild herbivores. The early Utah pioneers observed this grass growing abundantly over many of the desert ranges where it sometimes formed almost pure stands (Dayton 1937). From 1880 until about 1934, unregulated grazing reduced or eliminated this grass in large areas of its native range. With the estab- lishment in 1934 of the Grazing Service, now known as the Bureau of Land Management, unregulated grazing was eliminated and a period of range rehabilitation and improvement was begun. Controlled grazing since 1934 has reestablished Indian ricegrass on western Utah ranges and in many areas it has recovered sufficiently to form almost pure stands. Some ranges, nevertheless, appear to be damaged by causes other than over-grazing. The possibility that some of the destruction to this grass might be due to factors other than heavy or unregulated grazing was not suspected until 1966 when Ralph Holmgren of l 2 the United States Forest and Range Experiment Station observed a high percentage of dead and dying stems of this grass on some ranges. A closer examination revealed small white insect larvae feeding on the underground stems and roots of the damaged plants. A review of the literature produced no indications that insects might be deleterious to this grass. The study has demonstrated that three species of insects feed on the roots and underground portion of the stems of Indian ricegrass. Two of these are larvae belong- ing to the moth family Pyralidae and the third is a larva of the beetle family Cerambycidae. The objectives of this research were to determine the taxonomic identity of the insects which damage Indian ricegrass, to determine the extent of damage to this grass at selected sites, and to study, insofar as time and circum- stances permit, the life cycle of the insects. REVIEWOF LITERA'IURE

Indian ricegrass, oryzopsis hymenoides, belongs to the tribe Stipeae, Subfamily Festucoideae of the grass family Graminae (Gould 1968). It is a hardy, drought- resistant plant which can endure the harsh environmental conditions found in the desert areas. Individual plants produce an abundance of herbage that is very nutritious and is highly palatable to all classes of livestock (Dayton 1937). The large seeds are also high in food value and are sought after by wild animals such as rodents and birds. The seeds were formerly gathered by the Indians and used as one of their food staples (Stevenson 1915). From the early 1880•s until about 1934, unregulated overgrazing greatly reduced the abundance of Indian ricegrass from many ranges of western Utah (Rogler 1960, Verner 1956, and Plummer 1952). When grazing pressures were relieved, the rice-grass began to recover slowly by natural means and, in the most depleted areas, by reseeding. How- ever, due to seed dormancy and low germination, most reseed- ings failed (Rogler 1960). The three species of insects which were found to damage Indian ricegrass were not known to feed on this grass prior to this study, in fact, one of the three species was new to science prior to this study.

3 METHODSAND PROCEDURES

This research was conducted at the Desert Experi- mental Range of the Intermountain Forest and Range Experiment Station of the Forest Service of the United States Department of Agriculture, located in Millard County, forty-seven miles west of Milford, Utah. This area is climatically marked by great temperature extremes, low precipitation and strong desicating winds. Three areas which differed in vegetative composition were selected for investigation. Two areas are approximately four to five miles west of the Desert Experimental Range Headquarters. They are known as Warm Cove, which is a Shad- scale-Indian ricegrass (Atriplex-oryzopsis) community, and overflow which lies approximately three miles northeast of Warm Cove and is a Winterfat-Indian ricegrass-Shadscale (Eurotia-Oryzopsis-Atriplex) community. The third area lies twelve miles southeast of the Desert Experimental Range Headquarters in Pine Valley. This is a Little Rabbitbrush- Winterfat-Indian ricegrass (Chrysothamnus-Eurotia-orwo_psis) community. An area in Tintic Valley, south of Eureka, which is predominantly an Indian ricegrass community, was also examined, but no root or stem-feeding insects were found. This research was conducted between March and October of 1972. Data were collected during the spring and 4 5 summer, and the study was terminated in August vhen the new growth (green stems) began to dry. Indian ricegrass is a bunch grass technically called a clone of individual plants. Each individual plant may develop several tillers. The tillers arise from basal nodes and grow within older dead sheaths. In this study, the word stem is used for tiller and the word plant represents a bunch or cluster of tillers. Damage is interpreted as any physical destraction which is caused by the feeding activity of an insect. Injury due to grazing or other factors was not included. The Quadrat Method was used in measuring the number and size of plants in a given plot or area, and in this study encompassed 20 square meters. Indian ricegrass plants were classified into four size categories determined by the maximum diameter at the ground level. These categories area Oto 3.9 cm, 4 to 6.9 cm, 7 to 9.9 cm and those larger than 10 cm. These size categories also reflect the age of the plants. The plants vith a basal diameter from Oto 3.9 cm are Oto 2 years old1 those 4 to 6.9 cm are 2 to 3 years old, and those 7 to 9.9 are more than 3 years old. The age of plants more than 10 cm could not be determined, but evidently exceeds 3 years. Plants were selected from each quadrat, and the number of plants, infested or uninfested, per size category was determined. Damage to Indian ricegrass was determined by examining randomly selected individual plants of each size 6 category. The nwnber of stems from the previous growing season (old dried stems) and those of the current growing season (new green stems) were counted. At the same time the number of damaged stems from the previous and current growing seasons were also counted. The number and type of larvae causing the damage were counted and recorded. The larvae were classified according to size as small, medium and large. To study the life cycle and general biology of the three species, infested plants were collected and placed in one-gallon wide-mouth glass jars. These jars were kept in the laboratory at room temperature and observations made on the time and duration of the pupal stage and the date of emergence of the adult insects. Field observations were also made on the general biology and mode of feeding of the three insects. RESULTS

The two pyralid moths were identified as Coenchroa

illibella (Hulst) and Diatraea sp. by Dr. Douglas c. Ferguson of the u.s. National Museum, Washington, D.c. The latter of these was not identified to species due to lack of material reared from Indian ricegrass. Field collecting was not attempted for fear of collecting other closely related species. The third species, in the beetle family Cerambyci- dae, is a new species presently being named Typocer~s cera- taicornis by E~ G. Linsley and J. A. Chemsek (Figure 1). The hosts of these species were not known prior to this study. The number of plants per 20 square meters arranged according to size of plant for each of the three study areas is shown in Table 1. Graph 1 shows the percentage of damage of plants in each size category. Table 2 shows the range, mean and standard deviation of the new stems produced from uninfested plants in each of the study areas. Table 3 shows the range, mean and standard deviation of the stems produced from the infested plants. The difference between the mean number of stems produced from the uninfested and infested plants represents a loss in the production of new stems by the infested plants (Tables 2 and 3). The average dry weight for each individual stem is 7 8 .28 gram. The weight was determined by weighing fifty bundles of naturally dried stems which were cut at the ground level of uninfested plants. These plants vere selected from Warm Cove and overflow. A figure attained by multiplying the mean number of nev stems by the mean number of plants per 20 square meters was used to determine the mean number of new stems produced for that area. Multiply- ing the mean number of new stems per 20 square meters by the average weight per stem gave the mean weight of stems per a 20 square meter area (Tables 4 and 5).

Estimated Loss in Kilograms per Hectare

At Warm Cove there was a mean number of 2,302 stana produced from the uninfested plants in a 20 square meter area. A mean number of 1,708 stems were produced from the infested plantsJ therefore, there was an average reduction of 594 stems due to a combination of the three insect species. By the following formula the average dry weight of herbage lost per hectare can be calculateda

594 stems x 1 28 g X 20 m2 X 10,000 m2 ao. 3 Kg/Ha

Damage to the Overflow area was much higher. A mean number of 1,476 stems were produced from the uninfested plants and only 923 new stems from the infested plants. This resulted in an average reduction of 554 new stems per 20 square meters or 70.7 Kg of dry weight of herbage per hectare lost due to the feeding activities of the three insects. Table 1 Number of Indian Ricegrass Plants Arranged by Basal Diameter. Size Categories for Each Study Area. Shoving Range (r). Mean (x). and Standard Deviation (SD). per 20 m2

Location Plant Size Categories r X SD

Pine Valley 0 - 3.9 2 - 5 3.2 .9 4 - 6.9 2 - 6 3.8 1.1 7 - 9.9 4 - 8 6.3 1.2 10 - + 5 - 9 7.8 1.0 Warm Cove 0 - 3.9 18 - 64 36.4 14.2 4 - 6.9 5 - 24 15.7 6.1 7 - 9.9 0 - 9 5.3 2.5 10 - + 0 - 6 2.3 1.6 Overflow 0 - 3.9 8 - 28 13.9 s.o 4 - 6.9 4 - 16 8.6 3.8 7 - 9.9 3 - 7 s.o 1.5 10 - + 0 - 8 2.6 2.2

'° Table 2 Number of Indian Ricegrass Stems from Uninfested Plants Arranged by Basal Diameter Size Categories for Each study Area Showing Range (r), Mean (x), and Standard Deviation (SD) for the Previous and Current Growing Seasons

Plant Size Previous Season Current Season Location Categories r X SD r -- X SD

Pine Valley 0-3.9 an 14-35 21.1 5.4 19-51 31.6 9.9 4-6.9 cm 38-59 48.7 6.1 43-101 58.5 12.6 7-9. 9 cm 78-112 94.7 8.7 94-140 114.2 11.7 10- + cm 126-213 179.5 23.7 191-306 232.0 27.4 Warm Cove 0-3. 9 cm 12-32 25.3 7.8 8-34 26.5 8.2 4-6.9 cm 36-56 39.6 7.4 32-57 40.6 8.7 7-9.9 an 52-100 77.8 10.a 15-97 77.8 19.6 10- + on 114-301 168.0 32.4 155-311 224.8 29.4 Overflow 0-3.9 cm 13-36 20.5 s.a 8-32 21.7 6.9 4-6.9 cm 33-61 36.9 9.6 17-55 38.6 11.2 7-9.9 cm 54-170 65.2 22.5 53-80 65.6 10.s 10- + cm 159-291 219.9 45.6 94-211 l.58.0 47.B

...0 Table 3

Number of Indian Ricegrass Stems from Infested Plants Arranged by Basal Diameter Size Categories for Each Study Area Shoving Range (r), Mean (x), and Standard Deviation (SD) for the Previous and Current Growing Seasons

Plant Size Previous Season Current Season Location Categories r X- SD r X SD

Pine Valley 0-3.9 cm 14-36 22.1 4.2 13-49 30.2 a.s 4-6.9 an 41-56 48.0 s.o 45-70 53.9 11.4 7-9.9 cm 87-112 101.3 8.9 98-140 116.9 12.a 10- + cm 116-189 179.2 19.1 118-226 224.S 13.5 Warm Cove 0-3.9 cm 14-35 26.4 7.3 2-30 16.8 10.4 4-6.9 cm 32-56 43.4 7.5 23-57 34.3 10.3 7-9.9 en 71-100 80.2 9.2 15-70 61.0 24.0 10- + cm 133-157 147.2 11.8 70-150 103.4 34.1 overflow 0-3.9 cm 15-36 21.7 5.J. 4-23 12- 9 7.1 4-6.9 cm 35-65 36.8 9.5 4-43 27.6 13.1 7-9.9 cm 59-170 70.3 20.9 18-65 45.9 17.9 10- + cm 147-284 213.6 47.3 21-197 105.6 17.2

... Table 4 Number of Indian Ricegrass Plants at Warm Cove, Arranged by Basal Diameter Size Categories for Uninfestr and Infested Plants Showing the Mean Nwnber of Plants per Plot ( 20 m ) , the Mean Number of New Stems per Pl~t, and the Estimated Total Number of New Stems per Plot ( 20 m )

Plant Size Mean No. Pl~nts Mean No. New Hypothetical N~. Categories per 20 m Stems/Plant New Stems/20 m

(Uninfested) 0-3.9 cm 36.4 26.5 965.7 4-6.9 cm 15.7 40.6 638.2 7-9.9 cm 5.3 77.8 414. 7 10- + cm 2.3 124.8 283.3 Total 2,301.8 (Infested)

0-3.9 cm 36.4 16.8 609.7 4-6.9 cm 15.7 34.3 538.8 7-9.9 an 5.3 61.0 325.1 10- + cm 2.3 103.4 234.7 Total 1,708, 3

...N Table 5 Number of Indian Ricegrass Plants at Overflow, Arranged by Basal Diameter Size Categories for Uninfested and Infested Plants Showing the Mean Number of Plants per Plot (20 m2), the Mean Number of New Stems per Plant, and the Estimated Total Number of New Stems per Plot (20 m2)

Plant Size Mean No. Plants Mean No. New Hypothetical No. Categories per 20 m2 stems/Plant New Stems/20 m2

(Uninfested) 0-3. 9 cm 13.9 21.7 302.2 4-6.9 cm 8.6 38.6 330. 7 7-9. 9 cm s.o 65.6 327.9 10- + cm 2.6 158.0 415.5 Total 1,476.2 (Inf e.eted) 0-3.9 cm 13.9 12.9 178.8 4-6.9 cm 8.6 27.6 236-6 7-9.9 cm s.o 45.9 229.5 10- + cm 2.6 105.6 227.8 Total 922.7

w... 14

80 75

70 I'll .µ 65 \ ~ \ I'll s:: 60 \ 1-4 55 I \ ~ I 50 \ overflow - \ iO'l I ,a 45 ij ca I \ 40 I I'll .µ \ s:: 35 I ....RS - Warm Cove \ llt 30 \ 1M 0 25 \ a, O'l 20 \ .µ "'fij \ u 15 \ b t 10 llt 5 4 Pine Valley .._ 3 .. -o--. 2 ..--- ...... __. 1 .. --··--·· -0-··-··- ·- ··~ 0 ..-- ......

0-3.9 cm 4-6.9 cm 7-9.9 cm 10+ cm

Graph 1 Percentage of Plants Damaged by .!YRQceris ceraticornis, Diat.raea sp. and £oenchroa illibella in Each of Four Classes Arranged by Basal Diameter of Indian Rice- grass Plants in Warm Cove, Overflow and Pine Valley 15

20 19 18

N 17 Ei 0 16 N,.. a, 15 Q. ....Ul 14 C: k 13 8 ....., 12 RS k a, 11 ~ u Overnow Cl) 10 \ •rot a,M u 9 \ 0 8 \

1M 7 \ 0 \, ,... _ Warm Cove a, 6 5 1z a, 4 CJ) I RS k QJ 3 I > < 2 1 ' 0

0-3.9 cm 4-6.9 cm 7-9.9 cm 10+ cm

Graph 2 Average Number of Typoceris ceraticornis in Each of Four Classes Arranged by Basal Diameter of Indian Ricegrass Plants in Warm Cove and Overflow 16

male fenale

Figure 1 Pupae and Adults of TypOceris ceraticornis 17

Figure 2

General View of Warm Cove. Desert Range Experiment Station. 47 Miles West of Milford. Utah August 1972 18

Figure 3 General View of Overflow. Desert Range EJCperiment Station. 47 Miles West of Milford. Utah August 1972 19

Figure 4 General View of Pine Valley, Desert Range Experiment Station, 47 Miles West of Milford, Utah August 1972 20

Figure 5 An Indian Ricegrass Plant Infested by Typoceris ceraticornis Showing the Ladt of New Stems (Warm Cove, August 1972) 21

A B Figure 6 (A) Coenchroa illibe1la Larva and Cocoon, (B) Damage to Indian Ricegrass Plant 22

Figure 7 Diatr ·aea sp. Feeding on Roots of Indian Ricegrass 23

Figure 8 Larvae of 'fYPoceris ceraticornis and General Area on the Indian Ricegrass Plant Where Damage Occurs 24

Figure 9 Pupal of Typoceris ceraticornis in Pupal Cell at the Base of Indian R1cegrass Plant DISCUSSION

Indian ricegrass at Warm Cove and Overflow shoved an overall unthrifty appearance, especially the infested plants as shown on Figures 2, 3, ands. In Pine Valley, however, the plants grew taller and greener and produced more new stems than in any of the areas studied (Figure 4). Figure 5 shows the condition of an infested plant of the 7 to 9.9 cm size category.

Pine Valley £oenchroa illibella (Hulst) was the only stem-boring insect which damaged Indian ricegrass in this area. Table 2 shows the mean number of stems produced from the uninfested plants. Table 3 shows the mean number of stems produced from the infested plants. These tables show that there is no marked difference in the production of new stems between the uninfested and the infested plants. This suggests that this insect is of minor economic importance in reducing productivity of Indian ricegrass.

Warm Cove More than 60% of the 4 to 6.9 cm size category plants and approximately 80% of the 7 to 9.9 an size category plants were infested by either one or all three of the species in this area (Graph 1). The overall percentage of infestation was not as great as that of the Overflow area. 25 26 The mean number of new stems produced from the uninfested plants was greater than that produced by the infested plants as shown in Tables 2 and 3. Coenchroa illibella, Diatraea sp. and Typoceris ceraticornis were all found in this area, but the latter was the most destructive as shown by Graph 2.

2Y.!!flow The percentage of infestation in this area was similar to Warm Cove. More than 68% of the 4 to 6.9 c:m size category plants and 70% of the 7 to 9.9 cm size category plants were damaged by either one or a combination of the three insects found in this area. As in Warm Cove, Coenchroa illibella, Diatraea sp. and Typoceris _E!raticornis were found in this area, but again, the latter was the most destructive. The number of new stems produced from the uninfested plants was greater than that produced by the infested plants as shown in Tables 2 and 3.

~chroa illibella (Hulst) This species is easily recognized in its larval stage by the presence of a pale yellow cocoon-type resting nest made of silk and covered with small sand granules. This cocoon is found at an exit bored on the side of the stem and is usually above the ground surface (Figure 6A). A larva found within this cocoon appears to be in a resting stage. When the larva is disturbed it will crawl into the 27 stem through the exit hole. Each larva may bore from one to five stems during its larval development. All of the bored portions of the stems were below the surface of the ground. When the larva moves from one stem to another it usually enters an adjacent stem. It may either bore down towards the base of the stem or up away from the roots, from the point of entry, but it usually remains underground. If the larva bores towards the base of the stem it will feed on the growing part of the stem, and in so doing, the stem will not produce new growth (Figure 6B). The larvae collected and placed in rearing jars began to pupate from April 26 through May 23. The adults emerged from June 18 through July 13. Field observations revealed the presence of several larval stages throughout the year, but not pupae, which indicates that the species takes more than one year to complete its development. Pupae vere only found during June and July. The duration of the pupal stage in the laboratory was 35 ± 2.8 days. Pupation occurred within the silken cocoon mentioned above.

Diatraea .!It!. This species was collected from infested Indian ricegrass plants and placed in wide-mouth one-gallon glass jars for careful observation of its larval development. Unlike .£2.!!:!chroa illibella, this species does not construct a silken cocoon for pupation nor does it bore through the stems. All of the larvae collected were found at the crown of the roots and it was difficul.t to detennine the extent of damage 28 caused to Indian ricegrass. No roots were severely damaged, although there was evidence that the larvae had fed upon them (Figure 7). Larvae buried in the soil began to pupate from April 25 through May 31. Adults emerged from June 1 through July

28. The pupal stage required 43.8 ~ 3.3 days. This seems to be a very long time for pupation and it is possible that the larvae entered a pre-pupal resting stage before they actually pupated. Field observations revealed large numbers of larvae in various stages of development during most of the years however, the pupal stage was only evident from May 18 through June 27.

Typoceris ceraticornis Various sizes of larvae were found throughout this studyJ however, the pupal stage was only found from May 18 through June 23. No small larvae were found during the late winter or spring, but were very abundant in July and August, suggesting that the larval stage is longer than one year. Larvae collected from Indian ricegrass were placed in wide-mouth one-gallon glass jars for observation. As soon as a larva began to pupate, it was removed and placed in an individual wide-mouth quart jar and a record was kept of the duration of the pupal stage. In the laboratory the larvae began to pupate from April 28 through May 3 and the adults began to emerge from May 16 through May 23. However, in the field the adults emerged during the first week of 29 June. Some pupae were also found during the first week of June indicating that the adults probably emerged during the middle of June. The pupal stage, under laboratory conditions, took 20 t 1.0 days. No pupae or adults were found in the field during July. However, large larvae, measuring from 1 to 1.5 an were found from March through October. Small larvae, measuring less than 1 on and some measuring less than o.s an were found during July and August. The adults emerged during May and June and the smallest larvae were found only during July and August. This suggests that the female lays her eggs during June and possibly as late as July, although oviposition was never observed. The female evidently oviposits no more than two eggs per plant, at least two or three centimeters below the surface of the ground. Plants having a basal diameter between 4 to 6.9 and 7 to 9.9 cm were the size most frequently selected for oviposition by this species. Qnly three beetle larvae were found per 20 square meters on plants smaller than 4 cm and only an occasional larva was found in those larger than 10 cm (Graph 2). The fact that large larvae were found on plants larger than 10 cm can be attributed to the probability that the adult female beetle oviposited on the plant when its basal diameter was smaller than 10 cm. Since the larvae take more than one year to complete their development, the plant could have increased in size during that time. 30 The small larvae upon hatching begin to feed at the growing base of the stems. In all damaged plants examined, the larvae fed in the center of the plant. In a few cases there was evidence that the larvae started to feed at the side and then bored horizontally through the entire base of the plant. However, in all cases the most extensive damage was caused at the center of the plant (Figure 8 A and B). A majority of the stems were severed and consequently did not produce new stems during the growing season. When the larvae was mature, it bored vertically or parallel to the stems and constructed a pupal cell from its frass and pupates within the cell as shown in Figure 9. Usually only the base of the dried stems are eaten, nevertheless, some green stems are also damaged or destroyed as the larva feeds on an old stem which forms a sheath around the new growth. Another evidence that the larva feeds on green stems is the fact that the feces are sometimes greenish in color. Although larvae are present throughout the year, only a small, insignificant number of new stems are damaged. This is an indication that old dried stems constitute the major source of food for this species and perhaps the new stems are fed upon by accident as these are surrounded by the dried leaflets which surround most stems.

Field observation from March through October shoved that the larvae were present in all stages of their development. Pupae, however, were only found during May and June and possibly as late as July. 31 Livestock Grazing and ---insect Infestation Although not based on conclusive data, but on personal observation, it is possible that livestock grazing practices and the percentage of plants of the 4 to 6.9 and 7 to 9.9 cm size category in an area apparently are the 1110st important factors which explain why one area is infested and yet a nearby area is relatively free of the insect species studied. For example, plants of the 4 to 6.9 and 7 to 9.9 cm size category were more abundant in Warm Cove and overflow and least abundant in Pine Valley (Table 1). Further- more, Warm Cove and Overflow were grazed by sheep which are forb and browse feeders and grazing took place in the winter. Pine Valley was grazed by cattle which are mostly grass feeders and grazing took place from winter until spring. There- fore, Indian ricegrass plants not exposed to grazing from spring until winter in Warm Cove and overflow were attractive to the adults of all three insect species. Plants in Pine Valley, with cattle grazing during spring and summer, evidently were not attractive to _!ypoceris ceraticornis and Diatraea sp. It may be possible, following further investigations, to manipulate the insect populations through controlled grazing practices. CONCLUSIONSAND SUMMARY

Coenchroa illibella. Diataea sp. and Typoceris ceraticornis were the only insects found feeding on the roots and underground portions of the stems of Indian ricegrass. Typoceris ceraticornis (Graph 1) caused up to 80% of the damage to Indian ricegrass plants with a basal diameter of 7 to 9.9 cm at Warm Cove and up to 70% at the Overflow area. Warm Cove and Overflow had by far the greatest infestation and the most severely damaged plants. Damage was most severe on plants with a basal diameter of 4 to 6.9 and 7 to 9.9 cm. Plants in these size categories were also the most abundant at Warm Cove and Overflow. The least damaged plants were those smaller than 4 cm and those larger than 10 cm in diameter. Uninfested plants grew larger and produced a greater number of new stems. Those from Warm Cove and the overflow area showed an increase in the number of new stems, however. those from Pine Valley showed the greatest production of new stems. The infested plants at Warm Cove and overflow remained smaller and produced fewer new stems than old stems.

32 33 Those plants infested by a large larva of Typoceris ceraticornis usually produced no new stems. Plants with a medium size larva usually produce some new stems, but never as many as there were old stems. LITERA'IURECITED

Dayton, w. A. 1937. Manual of the Grasses of the United States. u.s.D.A. Gould, Frank, 1968. Grass Systematics. McGraw-Hill Book Co. Plummer, A. P. 1952. Increasing Stands of Indian Ricegrass. Agron. Jour. 44a 285-289. Rogler, G. A. 1960. Relation of seed dormancy of Indian ricegrass [oryzopsis hymenoides (Roem & Shult) Ricker] to Age and Treatment. Agron. Jour. 521 470-473. Stevenson, M. c. 1915. Ethnology of the Zuni Indians. u.s. Bureau Amer. Ethnol. Ann. Rept. (1908-1909) 30a 33-102. Verner, J. E. 1956. The Value of Indian Ricegrass in Range Reseeding. Jour. Amer. Soc. Agron. 32a 33-41.

34 THE EFFECT OF INSECT DAMAGE ON INDIAN RICEGRASS (ORYZOPSIS HYMENOIDES) IN WESTERN UTAH

Luis Guerra s. Department of zoology M.s. Degree, April 1973

ABSTRACT Indian ricegrass at the Desert Range Experiment Station forty-seven miles west of Milford, Utah, is damaged by the larvae of Coenchroa illibella, Diatrae sp. and ;lJ?Oceris ceraticornis, the latter being the most destruc tive. The biology of the insects and the extent of damage inflicted are discussed. Uninfested plants produced more new stems than infested plants. Plants having a basal diameter of 4 to 6.9 cm and 7 to 9.9 cm were the most frequently infested and, consequently, the most severely damaged. COMMITTEE APPROVAL, VITA

Luis Guerra s.