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Electronic Theses and Dissertations

1982

The Occurrence and Effects of grylli on Populations in South Dakota

Roger Allen Bohls

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Recommended Citation Bohls, Roger Allen, "The Occurrence and Effects of on Grasshopper Populations in South Dakota" (1982). Electronic Theses and Dissertations. 4128. https://openprairie.sdstate.edu/etd/4128

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OF ENTOMOPHAGA GRYLLI ON

G RA ~ S HOPPER POPULATIONS IN

SOUTH DAKOTA

By

Roger Allen Bahls

A thesis submitted in partial fulfillment of the requirements for the degree Master of Science Major in Entomology South Dakota State University 1982 THE OCCURRENCE AND EFFECTS

OF ENTOMOPHAGA GRYLLI ON

GRASSHOPPER POPULATIONS IN

SOUTH DAKOTA

This thesis is approved as a creditable and independent investigation by a candidate for the degree, Master of Science, and is acceptable for meeting the thesis requirements for this degree. Acceptance of this thesis does not imply that the conclusions reached by the candidate are necessarily the conclusions of the major department.

Burruss McDaniel /Date Thesis Adviser

f Maur1ce Horton ·oate Head, Department of Plant Science ACKNOWLEDGEMENTS

The author extends his sincere appreciation to Dr.

Burruss McDaniel for his advice, assistance and understanding during the course of this study and in the preparation of this manuscript. Sincere gratitude is also extended to Dr.

Robert J. Walstrom for his encouragement and advice.

Appreciation is extended to the following members of - North Dakota State University for their aid and advice, Dr.

Richard Frye, Dr. Walter Valovage, Dr. Greg Mulkern, and

Dave Nelson.

The author extends his appreciation to Dr. Gary

Larson for his help in the identification of plant spec_imens, and Dr. Ernest Hugghins for ·his advice in the final correction of this manuscript.

Special thanks is extended to Mrs. Irene Vick for her assistance in the preparation and typing of this manuscript.

The author is indebted to Kim Kennedy for her assistance during field and laboratory experiments, to fellow graduate student, Gerald Fauske, for his encouragement throughout this study, to Eileen, Marty, Greg, Yvonne, Nathan and Averie for their guidance and encouragement throughout the years. This research was supported by the Old West Regional

Commission, OWCR Grant #1007302, and also USDA Cooperative

~greement #1090-20261-021A in cooperation with South Dakota State University, Dr. Burruss McDaniel, principle investigator. RAB TABLE OF CONTENTS

Page INTRODUCTION. . . • • . . . • • . . • . . • ...... • • • . • • • . • • . • • . . . 1

LITERATURE REVIEW. • • . . . . • . . . • • • • • . • • • • • • . • • . . . • . • • . . . 6

F·ACTORS INFLUENCING GRASSHOPPER POPULATIONS...... 6

WEATHER. . • . • • • ...... • . . . • . . • • • • . . • • • . • • • • . . • . • • . . 6

HABITAT. . . • • . . . . . • . ... • . • . • . • • • . • . • . . . • • • . • . . . . . • • . 7

MICROORGANISMS...... 7

PENETRATION AND DEVELOPMENT ..•...•..••••.•.•.•... 10

DISEASE SYMPTOMS...... • • • • • • . . . . • . • • • . • • • . . . 12

STRAINS OF ENTOMOPHAGA GRYLLI .....•...... •.••.... 13 EPIZOOTIOLOGY ...... ••...•....•.•.....••.... 14

CONTROL ATTEMPTS WITH ENTOMOPHAGA GRYLLI .•..•.... 15

MATERIALS AND METHODS . . • . . . . . • . • • • . . . • . . • . . • ...... 17 SURVEY OF NATURAL OUTBREAKS OF E. GRYLLI IN SOUTH D.AKOTA. • • ...... • ...... • . • . . . . . • . . • . . • . . . . • . . . . . 17 NYMPHAL MORTALITY, BROOKINGS COUNTY, 1981 ••..••.... 20

PERSISTENCE OF CLINGING- KILLED . 22

RESULTS ...... •...... ~ . . . • ... . • ...... • . • . . . . 25 NYMPHAL MORTALITY...... • . . • . . • ...... • . • . . . . 2 5 PERSISTENCE OF CADAVERS...... 25 SURVEY...... • . . . • ...... • . . . . . • • . . • • • . . . . 2 7

WHITE RIVER- MELLETTE COUNTY ...... ~ .•••.... 32 POLLOCK - CAMPBELL COUNTY...... • . . . • . . . . . 3 3 DISCUSSION...... 34 TABLE OF CONTENTS (continued)

Page

LITERATURE CITED. • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 4 0

APPENDICES • • • • • • • • • • • • • • • • • • • • • • • • .. • • • • • • • • • • • • • • • • • 4 8 LIST OF ·FIGURES

Figure Page 1 Brookings nymphal mortality study site ... '21

2 Precipitation preceding 1981 E. grylli outbreak at the Stadium Road site ...... 23 3 Number of l ive grasshoppers ( .. ) and corpses of E. grylli adults (--) and nymphs (--) a t the Stadium Road site during 1981 .. . ~ ..•...... •..•.• ~ •.•.... 26 4 Percent o f c linging grasshoppers which were lost to t he ground. Data for Stadium Ro ad s ite based on 85 (-) ; data for I-29 site based on 296 insects (- -) ...... •..•.....•..... 28 5 Percent o f c linging grasshoppers with spores o f ~· grylli exposed to the environme nt. Data for Stadium Road site (--) b ase d on 85 insects; data for I-29 site (--) b ased on 296 insects ...... •.. 29

6 Observed occurrence of ~· grylli in grasshoppers, 1980-1981. 1 . M. bivittatus 2. M. differenti alis 3. M. femurrubrum 4. M. packardii 5. M. confusus 6. M. lak1nus 7. P. nebrascensis ...... :-...... •.. :-. . . . . 30 THE OCCURRENCE AND EFFECTS

OF ENTOMOPHAGA GRYLLI ON

GRASSHOPPER POPULATIONS IN

SOUTH DAKOTA

by

ROGER A. BOHLS

Under the guidance of Dr. Burruss McDaniel

ABSTRACT

The effect of Entomophaga gryll~ on grasshopper populations within South Dakota was investigated during a

2-year period. Field observations established that tbe state's 3 most important species of grasshoppers are susceptible to pathotype 2 infections. Outbreaks are believed to be initiated annually from the soil of undisturbed areas which act as the reservior for Entomophaga grylli resting spores. The occurrence of the fungus in regions of the state receiving 355 mm of rain during the growing season indicate pathotype 2 infection is maintained in dry environments. However, detailed epizootiol ogical studies of the fungus are needed before the potential of Entomophaga grylli, as a biological control agent, is established. INTRODUCTION Grasshoppers have posed a threat to man for centuries. Severe economic losses occur during outbreak years as grasshoppers compete with man and livestock for food. Grasshoppers are often the most destructive pests of cropland and rangeland in the United States (Cowan, 1958;

Onsager and Hewitt, 198--2; Parker and Shotwell, 1932; Pfadt, 1949). Annual average damage to crops and range in areas west of the Mississippi River was estimated at $75,000,000 during the 1950's (Cowan, 1958). Haeussler (1952) estimated that grasshoppers caused over $795 million damage to crops and rangelands from 1925 to 1950 in the United States.

Hewitt (1977) gives a detailed review of forage losses caused by rangeland grasshoppers over a 40-year period. A steady increase of grasshopper populations occurred on the Great Plains during the 1930's. Parker and

Shotwell (1932) reported that during the spring and summer of 1931 there occurred in South Dakota and Nebraska the most serious grasshopper outbreak in the United States since the days of the Rocky Mountain locust. Melanoplus bivi ttatus and Melanoplus differen·tialis destroyed 7 5% of the crops in a 44,041 square km area and 25% of crops over an additional 33,678 square kms. Also, during the

- 1 - 2

5-year period of 1937-41, grasshoppers caused an estimated loss of $42,303,030 to cereal, forage, and truck crops in South Dakota (Spawn, 1945) . McGinnis (1959) reported that during the past 100 years of agricultural history in South Dakota, 45 years have been years in which grasshoppers have destroyed the bulk of crops in localized areas. Surveys (United States Department of Agriculture, APHIS) show that outbreaks do not occur every year in South Dakota. However, favorable conditions for grasshopper development and survival occur frequently within the state. Therefore, periodic outbreaks can be expected in future years. Over the past few years (1976 to present) grasshoppers have once again devastated South Dakota. Davidson (1979) believes the outbreak may have been the largest in the history of the United States. Kantack (1981) reported the heaviest grasshopper infestation on c~opland in the state in almost 20 years. These events led to the spraying of oyer 404,858 ha of cropland and almost 242,9l4 ha of ra~gela nd in the state for 1981. Within South Dakota there are two groups of injurious grasshoppers considered to be of economic importance. Species of importance are grouped into rangeland and cropland species (Appendix A) . The most 3

damaging of these species is M. differentialis, ~- bivittatus, and M. femurrubrurn. Other species of occasional importance are M. sanguinipes and C. pellucida.

Together these 5 species account for 90% of all grasshopper damage occurring within the United States. In South Dakota the average grasshopper hatch will begin by mid-May in the western and southern regions. There may be a variance

.. in the hatching date of approximately one month between different regions of the state. Also, among the state's

3 most important species of grasshoppers there may be a 3-week difference in hatching dates. Of these, M. bivittatus is considered an early hatching species and may appear 2 to 3 weeks prior to the first emergence of either M. differentialis or M. femurrubrum. Due t o the possible widespread devastation caused by grasshoppers , the problem of control has been one not only of private individuals, but one of public responsibility. Federal funds are not available for spraying grasshoppers in cropland areas. However, organized control programs on rangeland have been supported by federal a i d which paid one-third the total cost per acre of spraying. Nevertheless, such programs are usually crisis oriented and during the hot, dry years of grasshopper outbreaks, the benefits of using expensive chemicals is not justified from a farmer's standpoint. 4

Management of grasshoppers in the past 3 decades has relied heavily on broad-scale application of insecticides. These insecticides are not specific for grasshoppers and will kill the natural enemies of grasshoppers as well as other beneficial insects. Many insecticides are extremely toxic, limiting their use to commercial applicators only. Also, waiting periods may be required between the time of application and harvest or grazing of the treated area. The development of a system utilizing biological control agents, selective pesticide use, and cultural control methods would help reduce grasshopper damage. Alternative control methods such as microbial pesticides, parasites, a nd predacious insects is well documented (Steinhaus, 1963; Burges, 1981). Advantages of these methods include the safety of their use, lack of harmful effects on beneficial insects, and possible long-term control with little or no resistance. The use of the fungus Entomophaga grylli is currently being investigated as a tool in the management of grasshopper populations. Research cond~cted during the summers of 1980 and 1981 consisted of 3 separate studies. The primary focus of these preliminary investigations .was to determine the influence of natural 5

outbreaks of E. grylli on grasshopper populations within

South Dakota. The following specific objectives were formulated:

1) to locate the presence of E. grylli in South Dakota

2) to determine species of grasshoppers infected by E. grylli, and their population densities before and after infection

3) to determine the influence of host behavior and abiotic factors on the epizootiology of natural E. grylli outbreaks.

The occurrence of E.· ~rylli within grasshopper populations is essentially controlled by 3 general factors: the pathogen, the susceptible host, and the proper climatic conditons. These general factors can be separated into more precise factors such as moisture, temperature, light, inoculum concentration, and host density. Natural E. grylli outbreaks were not correlated with the above factors due to difficulty in obtaining accurate measurements at disease locations. 6

LITERATURE REVIEW

FACTORS INFLUENCING GRASSHOPPER POPULATIONS

WEATHER The most i mportant factor influencing grasshopper populations i s weather (D empster, 1963; Edwards, 1960;

Gage and Mukerji, 1 977 , Rodell, 1977). In general, warm, sunny, dry weather favors high survival, rapid development and maximum e gg p rodu cLion (Parker , 1930; Pickford, 1966).

Cool, wet c onditions freque n tly increase mortality, delay development and maturation and reduce egg laying periods

(Shotwell, 1941; Demps t er, 1963; Pi ckford, 1966). Consequently, warm, dry s ummers wit h adequate food available for normal development and reproduction are important factors leading to grasshopper outbreaks. In addition, insects generally benefit from increased consumption of foods containing h igh levels of nitrogen (Slansky and Feeny 1977). During drought years amino acids i ncrease in vegetation due to stress imposed upon plants (Hsiao, 1973). Haglund (1980) reports that grasshoppers detect and preferentially feed on grasses treated with amino acids. This ability to detect amino acids may l e ad to i ncreased growth and survival of grasshopper popu l a tion s that are concentrated on drought . stressed plant s. 7

HABITAT

Many environmental changes that alter grasshopper populations are directly related to agricultural practices.

The breaking of native sod and drainage of marshy areas for agricultural development are directly related to grasshopper increases (Bird et al. 1 966; Smith, 1969; Uvarov, 1956).

New combinat ions or c hanges in the proportions of crops grown in an area can greatly increase or decrease grasshopper populations (Isely, 1942 ; Sanderson, 1939; Barnes, 1959).

Allowing lands to become overgrazed enhances the population growth of grasshopper species normally associated with rangelands (Pepper , 1 955; Scoggan and Brusven 1973). The accumulations of weeds within cultivated fields or nearby field margins provide g r asshoppers with an extra source of available food (Barnes, 1959; Butcher, 1940; Smith, 1969). Ideal environme n t s for the development of grasshopper populations were created when roads with steep ditches were built. These areas provided additional oviposition sites that contained adequate food and shelter for grasshopper development (Barnes , 1959; Butcher, 1940; Smith, 1969).

r1ICROORGANISMS

Members of the family are infected by several speci es of fungi, bacteria, and protozoa (Steinhaus, 8

1949). Some of these microorganisms can cause severe

population reductions within grasshopper populations. The use of Aerobacter aerogens var. acr·idio·rium (d • Her.) to control grasshoppers was the first well publicized event in which a bacterium was used to control an . The use of

a protozoan, Nosema locustae Canning has been effective in reducing some grasshopper species (Henry, 1971; Henry et al.

1978; Henry and Onsager , ~ 982) and may also affect the fecundity of infected female survivors (Henry, 1981). After reviewing the works o f others, Roffey (1968) stated that all stages of grasshopper development are susceptible to infection by fungi.

The early taxonomic history of the has been reviewed by MacLeod (1963) and Gustafsson (1965). The family Entomoph thora ceae contains approximately 200 species. The fir s t genus of the famil y, described by Cohn (1855), was named Empusa, and based on Emp·usa muscae Cohn, the type species. Fresenius (1956) proposed Empusa was unacceptable and t hat the genus should be named . Currently, several taxonomic controversies pertaining to this group of fungi remain unresolved. The most comprehensive taxonomic scheme was that proposed by Batko (1964 a-d, 1974; from Burges, 1981) which separated species into five genera and four subgenera. Following the proposals of Batko, t he fungal pathogen of grasshoppers will be referred to in this study as Entomophaga grylli. 9

Entomophaga grylli (Fresenius) was first described by Fresenius (1856) attacking a species of Gryllus near .

Frankfurt, Germany. ~· grylli is best known as a pathogen of grasshoppers and locusts. · The fungus is commonly found attacking insects throughout the world (F~esa, 1971;

I Gyllenber 1974; Mackie, 1923; MacLeod, 1956; Milner, 1978;

Rao and Cherian, 1940; Roffey, 1968; Skaife, 1925).

E. grylli has frequently· been observed attacking susceptible species of grasshoppers across the United States (Charles 1941; Hayes and De Coursey 1938; Hutchison, 1963; Rockwood,

1950j Thaxter, 1888; Walton and Fenton, 1939).

In South Dakota, Severin and Gilbertson (1917) stated that at least two species of fungi were found to attack grasshoppers. Although these species were not identified in their report, collections were made of dead grasshoppers found clinging to the tops of alfalfa and grass plants. In addition, Riker mounts made by Severin include cadavers of M. bivittatus containing resting spores of

E. grylli. E. grylli plays a significant role in the natural control of grasshoppers and is the most important fungal pathogen of grasshoppers (Dempster, 1963). Both cropland and rangeland species of grasshoppers are susceptible to infection by E. grylli (Hayesand De Coursey 1938; Hewi~t, 1979; 10

MacLeod and Muller-Kogler, 1973; Pickford and Riegert, 1964;

Rockwood, 1950). Hewitt (1979) reported that E. grylli spreads swiftly and causes a rapid decline in grasshopper populations on Montana rangelands. Hayes and De Coursey

(1938) considered the fungus the most effective natura control, killing large numbers of adult grasshoppers. Roffey

(1968) and Kahn (1964) reported a high mortality among adult

Patanga succincta in Th-ailand. Chapman and Page (1979) re­ ported 10% of Zonocerus var~egatus, in southern Nigeria, died overnight and this rate sometimes continued for 2 or 3 nights.

In Canada, E. gry1li caused high rates of mortality within

Camnula pellucida populations (Pickford and Riegert, 1964).

Natural outbreaks of the disease were responsible for reducing grasshopper populations to a very considerable extent during the 1933-34 period in Nyasaland (Smee, 1936).

PENETRATION AND DEVELOPMENT

Infections from fungi via the alimentary canal occur rarely (Steinhaus 1949). Infection is initiated by a germ tube from some type of spore penetrating the insect'S integument. Penetration consists of a mechanical process and the secretion of enzymes that weaken or degrade the cuticle (Lefebvre, 1934; MacLeod, 1963; Sawyer, 1933;

Samsinakova et al. 1971). Smith et al. (1981) suggest that the complexity of the insect integument would require more 11

than one enzyme for penetration to be successful and that these enzymes act in a sequential manner.

It has been reported that the interval between infection and death has a wide variation. A five to six day interval is reported by Schaefer (1936), Skaife (1925), and

Roffey (1968). Whereas Pickford et al. {1964) suggest the fungus has a two-week incubation period within the host.

Also artificial infecti6n by injection of resting spores

(Nelson et al. 1982) and protoplasts (MacLeod, et al. 1980) into the haemocoel caused death in approximately two weeks.

Once penetration has been completed, the invading hyphae usually separate into component cells known as hypha! bodies (MacLeod, 1963). However, several modes of vegetative growth occur among the Entomophthorales (Burges, 1981). The formation of hypha! bodies may begin at the initial phase of penetration of t he insect cuticle by the fungus (Prasertphon and Tanada 1968 ) or be delayed until death of the host (Thaxter

1888i Ullyett and Schonken, 1940). Prasertphon and Tartada

(1968) report that the size of the fungal bodies and sites of their multiplication may explain how fungi spread throughout the host. Hypha! bodies much larger than insect haemocytes would not circulate freely in the haemolymph, while relatively small hyphal bodies would be unimpeded as they circulate in the haemolymph. Skaife (1925) observed hyphal bodies of E. g·rylli circulated to all parts 12

of the body via t he haemo1ymph in t h e red locust,

Cyrtancanthacris septemfasciata. After death of the host and with sufficient mo i sture, the hyphal bodies germinate giving rise to conidi ophor es (pathotype 1) . · These conidiophores emerge through the exoskeleton each bearing a single conidium (MacLeod , 1963). Conditions that are unfavorable f o r the development and survival of the fungus trigger the formation of r esting spores which are adapted to withstand such conditions. In the case of E. grylli, hyphal bod~es g i ve rise t o a resting spore form known as azygospores (Riddle, 1906) .

DISEASE SYMPTOMS Grasshoppers succumbing to i nfection by E. grylli behave in a characteristic manner. Disease symptoms normally do not appear until the d isease is in its advanced stages. Prior to death there may be a general restlessness, cessation of feeding, a nd l oss of coordination (Madelin, 1963). Infected individ uals tend to climb upwards on vegetation just before death and die with their legs wrapped around t h e plant. Foll owing death there may be a distention of the abdomen to a lmost twice its original size. The grasshopper body becomes soft a nd pulpy and is easily broken up if disturbed. At this time the abdomen often curls upwards and forwards to the extent that it almost touches the pronotum 13

{Schaefer, 1936).

Approximately one hour after death there may appear a white, furry growth covering the insect's body. The makeup of this growth is club-shaped sporagenous cells which project from the insect's integument like close set hairs (MacLeod and

Muller-Kogler, 1973). This form of the fungus is equivalent to Soper's (1980) pathotype 1. Walton and Fenton (1939) and

Skaife {1925) indicated an absence of a fine furry growth on infected grasshoppers. In such cases the insect is filled with azygospores, which Soper (1980) identified as pathotype 2.

STRAINS OF ENTOMOPHAGA GRYLLI

Certain species of_ grasshoppers appear to be unaffected by E. grylli. Skaife (1925) noted that Eugaster spp. were very abundant in disease locations; however, none became infected with the fungus. In Canada,· PTa·tybo·thrus bru·nneus did not succumb to the disease even though it was intimately associated with diseased c. pellucida (Treherne and Buckell, 1924). Also in Canada, Melan·oplus· sang·uinipes appeared to be immune to

E. grylli. Different strains of fungus were found to be lethal to different grasshopper species according to Pickford and Riegert (1964) . Soper (1980) identified two different pathotypes of E. grylli. Pathotype

1 has a typical entomophthoralian life cycle with conidia 14

and resting spore states. This pathotype has been isolated

from field populations of Dissostiera carolina and Camnula pellucida and from l aboratory infected Locusta migratoria.

Pathotype 2 lacks the conidial stage in the field and is restricted to Melanoplus spp.

EPIZOOTIOLOGY

The precise factors controlling the occurrence of

E. grylli outbreaks i s unknown. Approximately two weeks of heavy and continuous rains are reported preceding outbreaks of E. grylli (Pickfor d and Riegert, 1964; Roffey, 1968).

Skaife (1925) reported that a rainfall of 154 mm over a three month period was sufficient to start and maintain an epizootic of E. grylli. Development of the fungus · has been reported as being dependent on rainfall which acts as an important source of surface water on the insect (Balfour-Browne, 1960; Chapman and Page, 1979). Apparently surface water enables spores to adhere long enough to the integument for the processes of germination and penetration to be completed. Epizootilogical studies conducted within aphid populations revealed that inoculum levels and host density were of major importance; and disease incidence was not limited by climatic factors

(Soper and MacLeod, 1981). The spread of a pathogen within an insect population can be influenced to a large extent by environmental conditions. When initial infection is established, rainfall 15

is considered an essential element for the continued spread of the disease (Pickford and Riegert, 1964; Walton and Fenton,

1939). Dempster (196 3 ) states that there is a positive correlation of maximum spread of fungal diseases with low wind velocities, high humidities and relatively high tempera­ tures.

The normal habits of the host insect play an important role in the dissemination of insect pathogens. Tanada (1959) considers the movement of infected grasshoppers to be the primary method of disseminating the fungus. The habit of grasshoppers aggregating in small areas, creating dense populations, aids in the spread of the disease which can then reach epizootic proportions (Pickford and Riegert, 1964;

Walton and Fenton, 1939). The positioning of E. grylli cadavers high atop vegetation gives a wide dispersion of liberated fungal spores (MacBain Cameron, 1963; Thaxter, 1888). Healthy insects feeding on diseased cadavers is another factor contributing to the spread of some fungi (Sweetman, 1963) .

CONTROL ATTEMPS WITH ENTOMOPHAGA GRYLLI Various attempts have been made to infect healthy grasshoppers with E. grylli. Skaife (1925) and McMartin (1935) conducted experiments in which E • . g·rylli resting · spores, conidia, and hyphal bodies were fed to grasshoppers. They concluded that infection does not occur when grasshoppers 16

ingest E. grylli . Walton and Fenton (1939) reported that grasshoppers consuming hypha! bodies and resting spores in their diet have died from mycosis. However, E. grylli spores may have come in contact with the insect's integument as the bran s pore mixture was left in the cages containing the grasshoppers for six days. MacLeod (1963) stated that obtaining infection by artificial inoculations with members of the Entomophthorales was very uncertain. No mortality was observed in experiments when~ore sprays and resting spore pastes of E. grylli were applied to grasshoppers (Schaefer, 1936; Skaife, 1925; Smee, 1936). The use of old and fresh con~dia collected from vegetation and diseased specimens failed to infect healthy grasshoppers (Schaefer, 1936). However, Petkov (1939) obtained a 83% kill of Caloptenus italicus in Bulgaria after scattering spores of E. grylli on plants. Furthermore the previously mentioned injection techniques of Nelson et al. (1982) and MacLeod et al. (1980) have proven to be successful. 17

MATERIALS AND METHODS

Determining the influence of E. grylli on grasshopper populations within the state was accomplished by the following specific objectives:

1) to locate the presence of E. grylli in South Dakota

2) to determine species of grasshoppers infected by E. grylli, and their population densities before and after infection 3) to determine the influence of host behavior and abiotic factors on the epizootiology of natural E. grylli outbreaks. ·

SURVEY OF NATURAL OUTBREAKS OF E. GRYLLI IN SOUTH DAKOTA A survey was conducted to determine the natural distribution of ~. gryl.li within grasshopper populations.

Factors recorded throughout the course of the investigation are the general climatic conditions preceding outbreaks of the fungus, the species of grasshoppers succumbing to infection by E. grylli, and the ecological make-up of the areas in which natural outbreaks were found.

An examination of USDA-APHIS grasshopper surveys led to the establishment of 10 field stations in the following counties: Lyman, Todd, Mellette, Stanley and Jones. Grasshopper densities at each of these 10 stations were estimated weekly by taking 100 sweeps with a stand~rd insect net sampler along each of 3 transect lines. 18

Vegetation at these sites consisted primarily of

Agropyron smithii and Buchloe dactyloides. Grasshopper species encountered were those normally associated with grasslands as listed by Hewitt (1977) (Appendix B).

Additional information as to the whereabouts of

E. grylli outbreaks within grasshopper populations was obtained by contacting county agents in regions heavily infested with grasshoppers.

After an initial outbreak w~s located, approximately

5-10 additional observations were made within that county.

An equivalent number of observations was conducted in surrounding counties. The majority of county records for E. grylli outbreaks were not discovered until the last summer of my research and, therefore, were not studied intensively.

However, the Stadium Road site in Brookings County and

White River sites in Mellette County were observed weekly. The Mellette County outbreaks were located approximately 402 km southwest of the SDSU campus. This ·region of the state lies within the Pierre Hills and is characterized by smooth hills and ridges. Mellette

County records are primarily based on observations at 1 of 2 alfalfa fields located along the edge of the Little White River. A deciduous growth consisting of Cottonwood, 19

Bur Oak, American Elm, and Chokecherry encompassed the east field, while the west field was bounded by trees along 3 of its 4 margins. Both fields contained substantial growth of Kochia, Russian Thistle, and Smooth Brame. The west field was harvested during the· first week of July and, therefore, served as a collection site for E. grylli spores. The east field was not harvested during the 1980 or 1981 seasons and most observations were conducted at this location.

The Stadium Road-Brookings County site is located within the Coteau des Prairies and is an area dominated by highlands with low hills and numerous lakes. Observations conducted at the Stadium Road site are discussed in detail in the Nymphal Mortality and Persistence of Corpse studies. The Pollock-Campbell County outbreak located in the northcentral region of the state is the largest outbreak observed. Pollock is located within the Coteau des Missouri and is characterized by highlands that are covered by glacial deposits and traversed by swales. The outbreak occurred on the North Dakota-South Dakota state line in barley fields. The adjacent barley fields were separated by a field border consisting of Kochia, Russian Thistle, and Annual Sunflower. 20

Annual average mean temperature and precipitation for South Dakota are presented in Appendix C.

NYMPHAL MORTALITY, BROOKINGS COUNTY, 1981

During the fall of 1980, a natural outbreak of

E. grylli was observed on the campus of South Dakota State

University (SDSU). This site (Stadium Road) is located approximately .2 km east and .2 km north of Coughlin-Alumni

Stadium. The Stadium Road site consisted of 0.2 ha of alfalfa. Collections of adult MeTan·oplus spp. killed by the fungus were taken from 5 September until the first killing frost on 12 October. Observations were made daily due to the convenient location of the outbreak. Therefore, the Stadium Road site was selected as the area for the

1981 nymphal mortality study. A drainage ditch at the Stadium Road site partitioned the field into 2 sections. From the southwest section of the field a 0.02 ha plot of alfalfa was selected as the area to be studied during 1981 (Fig. 1}. The plot was bounded by a cornfield along the south and by a gravel road along the west. The remaining margins of the plot were separated from other areas of alfalfa by clearings of approximately 18-46 m. STADIUM ROAD FJELD

24 r------·------~

GRAVEL ROAD DRAINAGE DITCH 12

6

0 I I I ! I I I I f I I If I I I I I I \ I I I I I I I ! I 0 6 12 18 24 CORN FIELD

Fig. 1. Brookings nymphal mortality study site. \ N (each division equals ·9.1 m) ~ 22

Field observat.ions o f mortality due to E. grylli were based on weekl y counts of live and dead grasshoppers.

The number of live ~:rr. ..1.s s hopper s per squa r e yard was estimated by using the pointe .r J\;(7'thod described by Onsager (1977).

Grasshoppers dying f ro;n the f u ngus were marked with colored flags. These flaq s we r.. .~ t aped to the vegetation on which dead, clinging g ·:- a ssh :lf -~~r s were found. Composition of economically i m p~. ·l rtan t ~... l a. s shoppers was estimated by taking

200 sweeps with a sta do:\ -r:d insect net sampler.

An examina· ..-;. n ;.•f weather records s hows that

substantial rai n fal 'Y. ~~ ! lt1/ mm) occurred during the 22-day period preceding the :f ~· .r.-~ t o bserved mortality on 10 August

(Fig. 2). Most of the ra 'nfall (77 nun) occurred during the first 5 d ays o f t he 22 -'"U:y period. During this period daily maximum t emper a t ures v. _ ~e d from 30°C and 1 8°C with a mean of

26°C. Daily mi n ' mum t . ·~wr rature ranged from 2ooc to 7°C with a mean o f 1 4 c.

PERSISTENCE OF CL I NGING-FUNGUS KILLED GRASSHOP PERS

The objective of this study was to establish the whereabouts of E. SEYlli spores formed in c adavers killed by the fungus . The persi stence of ~- grylli cadavers found clinging to the up per regions of vegetation was monitored for a 2-week period during September at 2 30

28 26

24 22

20 -.. 18 § 16 r-1 r-1 rd 14 4-1 .,.,~ rd 12 rx:: 10

8 6

4

2 0 20 22 23 24 27 28 30 1 2 3 5 9 July August

Fig. 2.Pr~cipitation preceding 1981 E. grylli outbreak at the Stadium Road site.

N w 24

locatio ns.

It was d etermined from field observations in

South Dakota during 1980-1981 that the majority of

E. gryll i outbreaks were occurring in alfalfa fields and roadside ditches. Thus, a r eas chosen for the study were limited t o these habi tats . An interstate highway ditch

(I-29) located 14 km south of SDSU and the Stadium Road sit e (see Nymphal Mortality) were chosen as the study s i tes.

Stadium Road observations were based on 64 adults and 21 nymphs, while the I-29 site contained 294 adults and 2 nymphs. Observations at both study areas were conducted daily and e ach cadaver was classified into one of t hree categories base d on the following: A - cadaver los t t o the ground

B - cadaver clinging wit h spore s exposed to the e nvir onment c - cadaver clinging with no spores exposed. Both sites received light rains and were subjected to strong winds. Weather i nformation was obtained from t he

SDSU meterological station. The Stadium Road and I-29 sites are located 0.4 km and 14 km from the weather station, respectively. 25

RESULTS

NYMPHAL MORTALITY

At the mortality site M. · ·femu·rrubrum was the dominant species making up approximately 85% of the grasshopper population. The remaining 15% consisted of equal populations of M. bivit·tat·us and M. dif·ferentialis.

All stages of M. femurrubrum, except first instars, were found dying from the fungus. Fourth instars were the youngest stages of ~- bivi tta·tus and M. di.fferentialis found succumbing to i nfe ction by E.· ·g·rylli.

During t he c our se of the study there was a decline in the grasshopper population from approximately 1.5 per square yard to .02 per square yard (Fig. 3). The total number of E. grylli cadavers flagged weekly also declined from 760 to only 2 during the last week of the study. The large number of immature grasshoppers flagged accounted for the majority of deaths due to E. grylli (Fig. 3) . Observations revealed that only resting spores were produced at the end of the infection cycle. Therefore, the form of E. grylli responsible for the recorded mortality at the Stadium Road site is equivalent to Sopers' (1980 pathotype 2.

PERSISTENCE OF CADAVERS

Fifty percent of the cadavers were lost to the 10,000 P------~

-.. Q) 1,000 r-1 cO cJ --..._ ..._ Cl.l bO 0 r-1 ...... ,. 100 ' Cl.l H Q) p., p . ' ...... ;.. ..c0 Cl.l ' Cl.l 10 cO H bO 4-1 0 \ H Q) 1 ~ \ z \

.1~----~------_. ______.______~----~------A ______. ______~ 0 1 2 3 4 5 6 7 8 9

Week

Fig. J . Number of live grasshoppers( .. ) and corpses of E. grylli adults(--) and nymphs· (--} at t he Stadium Road site during 1981.

r-v m . 27

ground by day 7 i.it ·t} e Stadium Road site and by day 8 at the I-29 site (Fig. 4). Many cadavers that remained clinging t o the veg~tatio n had major body parts missing or portions of the ·' ntcgument broken to the extent that spores o f ~ " S:J.. F~:.!.L... WP"~ · e lost to the ground and surrounding v";~T'·2 t.a t' ion (Fig. 5) .

Cl in~i · · ·r;._t cadav ·-:· s failed to produce an external growth of c ) ] .1 i oph J .~ s and conidia and t he infection cycle termi na .t·'J vi itl; ;J.•.e! production of resting spores only. These rc~·.Jtll~-~~~ ~ :··.:J ~ cate a typical pathotype 2

(Soper 1980 } (f~ tl 1:'<"~::_ }; ,)f E. grylli at both the Stadium

Road and I-29 ' i Ludy ;::: ·.- . es,

SURVEY

Du r i>•J the bu~.r ;a-n: s o f 1980 and 1981 natural outbreaks oi. :t;:, ~Y-.lJ. vJ·~~r e observed in 22 counties across

the state (Eig 6) D A total of 7 species of grasshoppers were found dy'ng fr m B~ grylli infections (Fig. 6).

Examinations of clin inJ cadavers at all locations revealed that only pathotype 2 was present as the infection cycle ended with ~ te Jroduction of resting spores only.

E. grylli was obse rved in grasshopper populations as early as the last week in June in the southcentral part of the state. Earliest observation of the fungus in eastern south Dakota was 1 July. Deaths resulting 100

"0 § 0 H b( r:: 0

CJ) H Cl) p. p. 0 ..c CJ) CJ) m H b(, 5

b(j r:: I ·r-t bO r:: ·r-1 I .--l u 4-4 I 0

~ ,...,.,--/ r:: Cl) u H / Cl) Il-l ____ _,_,___,

I 0 1 2 3 4 5 6 7 8 9 10 11 12 13 1'• 15 Days after death

Fig. 4 . Percent of clinging grasshoppers which were lost to the ground. Data for Stadium Road site based on 85 insects (--) ~ data for I-29 site based on 296 insects(--).

N (X) 100

"d Q) (J) 90 0 p.. :< QJ 80 (/) Q) H 0 p.. 70 (/) ...c: ·n+.I 60 ~

(/) H Q) 50 p.. p.. 0 ..c: (/) 40 (/) cO H on 30 4-1 0 -4-J j:j Q) CJ H Q) ~

0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Days af ter death

Fig. 5· Per cent of clinging grasshoppers with spores of ~· grylli exposed to the environment. Data f or Stadium Road site (--) based on 85 insects~ data for I-29 site (--) based on 296 insects. ~ '-0 SOUlU DAKOTA

1')4 10) 102 101 l(to) !!1!!1 !Ill t7 -,------r--- - -r --r- - - · - - - --, ----~--- · --r ---- ·- --1----

" · - ·46

,, ~ nnt•.tG WARS/fAIL '1 1.llff lt f !» f"IIIIVJ ':OifSC!N - · . \ ~ hir tJttL lw• l' .' li !lSOo\ IIO ROotN 1 ~ 2 1 ----<::AIIVI.'IfT/1c._r!_ CUMVAtDS I ~ )2 1_r~-=-- :lti ··~ 11Av-o-~--- - s-;;;;;;;:- f•rcR L1--.-.--_-.....~,_,00IN G . 1f'N --­ 4 ', DlVtt.

CL-,v- ·· -- '···- i..4AIL 1f"t - · '"'"'a- -se- ~-uRr rl''';l __•Nt;s . 3 I .. , ;

~;vn~ 12 3s6 lllNNtll' rooo 1 2

SCALC - S T'ATUT'C MILCS --=--=-===- 0 10 20 .Jo •o so ·----'-----L---_1 I I I ___J 1/Jl 102 101 100 , !18 !7

Fig.6. Observed occurrence of!· grylli in grasshoppers, 1980-81. 1.~. b ivittat us 2.~. differentialis 3.~. femurrubrum 4.M. packardii 5.M . confusu s 6.M. lakinus 7.P. nebrascensis. - - · w 0 31

from E. grylli infections were occurring as late as mid-October and late September in eastern and central parts of the state , r espectively.

The majori .y of grasshoppers dying from the fungus are found in areas not subjected to cultivation (field borders, roadside ditches, alfalfa fields). However, diseased grasshoppers were collected from the edges of cornfields (Brookings County) and soybean fields

(Davison Co unty) .

E. grylli outbreaks were observed in the following counties during the summer and fall of 1980: Mellette,

Tripp, Lyman, Meade, Charles Mix, Moody and Brookings.

Additional outbreaks located in the southeastern and northcentral regions of the state during 1981 included the following counties: Davison, Hanson, McCook, Sanborn,

Miner, Douglas, Hutchinson, Turner, Lincoln, · Bon Homme,

Yankton, Clay, Union, Campbell , and Walworth.

Grasshoppers dying from the fungus behaved in a characteristic manner. During the mid to late afternoon infected individuals could be located clinging to the tops of nearby vegetation and other structures such as barbed wire fences . Infected grasshoppers removed from their clinging positions exhibited slow, uncoordinated flexion and extension of the hind tibiae, while the first and second pairs of legs contracted as if the insect were 32

still clinging to t he vegetation. The majority of clinging cadavers were found with their heads directed toward the sky . Other cadavers were found positioned similar t o a moulting grasshopper with its head directed toward ·the ground. All cadavers failed to produce a external g r owth of c onidiophores and conidia.

WHITE RIVER - MELLETTE COUNTY

At White River M. bivittatus and M. differentialis were the dominant species with small populations of the following; M. confusus, ~· lakinus, and M. femurrubrum. Throughout the summer and fall of 1981, peaks of mortality occurred during the weeks of 6 August and 20·

August. Deaths due to E. grylli were recorded from 25 June until 1 October when the last field observations were taken. The normal inaccuracy encountered when estimating highly mobile insects such as grasshoppers, was further complicat ed due to the height of the unharvested vegetation. However, using an insect net sampler, the populatio n was estimated to be reduced approximately 40% over the period of early June to late August. 33

POLLOCK - CAMPBELL COUNTY

In August the harvesting of adjacent barley fields drove large numbers o f grasshoppers into vegetation along

the field borders. Du ring the last week of August large numbers of M. bivittatus and M. differentialis were found dying from E. grylli infections. The majority of deaths due to the fungus occurred within the 0.8 km field borders; howe v er, grasshoppers were found within the harvested b arley fields and surrounding prairie, also. 34

DISCUSSION

Research conducted during the 1980, 1981 seasons

established that the state's 3 most important species of grasshoppers are susceptible to pathotype 2 infections of E. grylli. In addition, other species of grasshoppers of importance t o South Dakota's croplands and rangelands are dying f rom natural outbreaks of the fungus.

Field observations suggest that only pathotype 2

infections occur within the state. Grasshopper species within South Dakota that are known to be susceptible

to pathotype 1 infections, apparently are not cross

infected by the pathotype 2 form of E. grylli. This

supports the findings of others (Pickford and Riegert, 1964;

Milner, 1978; Soper, 1980) that determined different

strains o f the fungus are lethal to different species of

grasshoppers. Nevertheless, from this investigation and

that of others, it is evident that in South Dakota, all

species of grasshoppers that are of immediate importance

and those that have the potential to be destructive in the

future are susceptible to either pathotype 1 or pathotype

2 infection of E. grylli. The transmission of E. grylli can be expected to

differ between pathotypes. Field observations have

determined that clinging cadavers dying from pathotype 1 35

infections produce an external growth of conidiophores

and conidia. Pathotype 1 cadavers producing and releasing

conidia to the environment provide a mechanism for the

rapid transmission of the disease. The ·lack of an

external growth of the fungus from pathotype 2 clinging cadavers indicates that this form does not have the same potential for rapid transmission as pathotype 1.

Although no production of conidia has been observed from clinging pathotype 2 cadavers, the possibility exists

that these spores do not contribute to the spread of

the disease until they reach the ground. Moisture levels are higher at soil level as compared to the elevated position of clinging cadavers. Therefore, spores at ground level are exposed to environmental conditions that are more favorable for the development of the fungus. The short period that E. grylli cadavers remain clinging to the tops of vegetation indicates that a large percentage of E. grylli spores are located on the ground throughout the year. Studies have revealed a minimal movement of fungal spores through the soil of most undisturbed agricultural ecosystems (Ignoffo et al. 1977;

Burges, 1950 ) . Therefore, most E. ~rylli spores produced from diseased grasshoppers may be available in the top layer of soil in undisturbed habitats. 36

The majority of deaths due to E. grylli are found

in uncultivated habitats. The location of E. grylli cadavers

within cultivated fields prob~bly resulted from the

movement of infected hosts from a , nearby undisturbed area.

Therefore , it is l ikely that the mechanical cultivation

of the s o . 1 dis urbs the host-pathogen interaction as

suggested b v Kalmakoff and Miles, 1980). These findings

sugges t t!1at the soil o f undisturbed areas acts as the

reservoir for E. grylli resting spores which initiate

outbreaks annually ~ Grasshoppers would most likely come

in contact with E. grylli spores at or near ground level.

Peak per iods of grasshopper activity at ground level take

place in the early morning hours and during periods of

cool, wet weather (Shotwell, 1941; Pickford and Riegert, 1964).

Infection of aphid populations (Hall, 1981) by

Verticill1um lecanii and lepidopteran larvae with

Nomuraea rileyi (Ignoffo et al. 1977) are alsb considered to

be initiated from micro-organisms located on the soil .

Other factors possibly contributing to the spread ' I of the fungus are ants, flies, spiders, millipedes, and

tettigoniids . All have been observed coming in contact with clinging E . grylli cadavers. Alternatively,

E. grylli spores may be splash dispersed onto hosts and

nearby vegetation by rainfall (Hirst and Stedman, . 1963). 37

It is concluded that E. g~ylli is unlikely to play any ma jor role in controlling grasshopper populations due to environmental requirements of the fungus (Pickford and Riegert,

1964; Riegert, 1968 ; Roffey, 1968). However, Chapman and Page (1979) reported E . grylli to be a key factor regulating grasshoppe r mortali y from year to year, even though the developmen t of the fungus was dependent on rainfall. In contrast, . ~ ch aefer, . 936 (from McMartin, 1935) reported that the development of the f ungus was not dependent on rainfall.

Conflicts over t he environmental requirements for the development of ~- grylli remain unsettled. Apparently unjustified conclusions have been reached about the development of E. grylli, since the factors controlling -the fungus are not completely understood. County records for the occurrence of E. grylli show the fungus Ls widespread across the state. The precise factors controlling the occurrence of such outbreaks is still unknown. However, the occurrence of the fungus in regions of the state receiving only 355 rnm of rain during the growing season (April - September) indicates the fungus is maintained in dry environments. Field results obtained by distributing fungus from infected grasshoppers are contradictory (Smee, 1936; Schaefer, 1936; Petkov, 1939). Regardless of these field 38

studies 1 attempt :-:~ slv~~ u ld be directed toward determining the n imirnum quan:L1.tf uf fungus required to obtain adequate control of gr;. ~':is rrppe· · p opulations. Accordingly, control methods s hou .....:l be L~ r E: ,; t .e d toward immature grasshopper population..:; vit, icr1 a.r ~. 1 ess harmful and occupy less area than adult grasHh JPJ)C": ~~ . t~J.so , with a 1- to 2-week interval be-

tween infect i -; n (:tJ Jd - ~ .. - ·1 · h of the host (Pickford and Riegert 1

1964; Skai :fe , .192~~ 1_· , t"::!(:omes n ecessary t o initiate control attempts b fore '::.r-:on c :ru l.~ dll y damaging s t ages of grasshoppers

are present .. 'J'l]· r~; t ::1•·. ·· 1 pl i cation of E. grylli to nymphal grasshopper po_ u.~ . r.::~ L:i c-':),~; t.hat are concentrated in hatching areas would be (; ... ~~; ir :~h 1.L.. Fighting ·grasshoppers before or at the t ime t.. ey ·; n. ·?

successful c c:unp.:d_9·n tf><·:L' J{er a nd Shotwell 1 1932). Uncultivated land is one Yr t .h<:-: ;. u"'~ t~ i:. ·• .o:rtLTTio n areas on which grasshoppers

hatch (Butcher. 194 ) 0 f atural outbreaks of E. grylli are usually ass ociat.ed \\'i.t-. 11 unc ltivated habitats . Therefore, the applic ation of a pi ·hogen in an undisturbed area is less likely to be subject ~d to factors that potentially alter the host-pathogen intera~tion. Detailed epizootiological studes of E. grylli in grasshopper populations have not been conducted. The discovery of several natural E. grylli outbreaks 39

across the state provides an opportunity to observe the fungus under a variety of field conditions. The observation of natural outbreaks in combination with replicated experiments controlling abiotic and biotic factors is needed before the potential of E. grylli, as a biological control agent, is established. 40

LITERATURE CITED

Balfour-Browne, F. L. 1960. The green muscardine disease of insects, with special reference to an epidemic in a swarm of l ocusts in Eritrea. Proc. Roy. Entomol. Soc. London (A), 35:64~74. ·

Barnes, 0. L. 1959. Effect of cultural practices on grasshopper populations in alfalfa and cotton. J . Econ. Ent. , 52:336-337.

Batko , A. 1964a. Entomophaga Mem. hors ser. 2,129-131.

Batko , A. 1964b. Bull . Acad. Pol. Sci., Ser. Sci. Biol. 12,319-321.

Batko , A. 1964c. Bull Acad. Pol. Sci., Ser. Sci. Bio1. 12,323-326.

Batko, A. 1 964d. Bull . Acad. Pol. Sci. , Ser. Sci. Bio1. 12,399- 402. Batko, A. 1974. In "Weolucja biologiczna: Szkice teoretyczne i metodologiczne" (C. Nowenskiego, ed.), pp. 209- 304. Polish Academy of Sciences, Institute of Philosophy and Sociology, Wroclaw. Bird, R. D. , w. Allen, and D. S. Smith. 1966. The responses o f grasshoppers t o ecological changes produced by agricultural development in southwestern Manitoba. Canad . Entomol., 98:11~1-1205. Burge s, A. 1950. The downward movement of fungal spores in sandy soil. Trans . . B~ . Mycol . Sco. 33:142-147. Burges, A. (ed.) 1981. Microbial control of pests and plant diseases 1 970-1980. Academic Press, New York and London. 949 pp.

Butcher, F. G. 1940. Ef fe~t of idle land upon grasshopper populations . J. Econ. Ent., 33~647-649. Chapman, R. F. and W. W. Page. 1979. Factors affecting the mortali ty o f the grasshopper, Zonocerus vari egatus, in southe rn Nigeria . J. Ecol., 48:271-288. Charles, v. K. 1 941 . A preliminary checklist of the entomogenou s f ungi of North America. USDA Entomol. and Pla n t Qua r antine Bur . , Insect Pe~t Surv. Bull. No. 21 ( 9) : 7 0 7- 7 7 9 . 41

Cohn, F. 1855. Empusa muscae und die Krandheit der Stuben fliegen. Nova Acta K. Acad. Caes. Leop.-Carol. Germ. Nat. 25: 301-360.

Cowan, F. T. 1 958. Trends in grasshopper research in the United States. Proc. lOth Int. Congr. Entomol., 3:55-58.

Davidson, E & 1979. A p lague of hoppers. Newsweek, 94(9) :35.

-Dempster, J. P. 1963. The population dynamics of grasshoppers and locusts. Biol. Rev. 38:490-529.

Edwards, R. L. 1960. Relationship bet ween grasshopper abundance and ~eather conditions in Saskatchewan, 1930-1958. Canad. Entomol., 92:619-624. Fresa, R. 1971. El hongo Ent-omophthora grylli en tucuras. Revista de Investigaciones Agropecuarias. Serie 5, Pathlogia Vegetal. Buenos Aires, 8:83-88.

Freseni u s, G. 1956. Notiz , Insekten-Pilze betreffend. Bot. Zeitung (Berlin) 14:882-883. Gage , s. H. and M. K. Mukerji. 1977. A perspective of g rasshopper distribution in Saskatchewan and i nterr elationship with weather. Environ. Entomol. 6 :469-479. Gustafsson , M. 1965. On species of the genus Entomophthora Fres. in Sweden. 1. Classification and distribution. Lantbrukshogskolans Ann_, 31:103-212. Gyllenberg , G. 1974. A simulation model for testing the dynamics of a grasshopper population. Ecol. 55:645-650. Haeussler, G. J. 1952. Losses caused by insects. In "Insects, The Yearbook of Agriculture", USDA, (Alfred Stefferud, ed.).

Haglund , B. M ~ 1980. Proline and valine-cues which stimulate grasshoppe r herbivory during drought stress. Nature, 288 :697-69 8.

Ha 11 ' R . A . 1981 . The f ungus Verticillium lecanii a s a microbial i n sect icide against aphids and scales. In, "Microbial control ·of pest and plant diseases 1970-1980". (H. D. Burges, ed.}, Academic Press , New York a nd Lo nd on ~ 949 pp. 42

Hayes, W. P., a nd J . D. DeCoursey. 1938. Observations of g rasshopper parasitism in 1937. J. Econ. Entomol., 31 : 519-522.

Henry, J. E~ 1971 . Expe r imental application of Nosema l ocustae f or con t rol of grasshoppers. J. Invertebr. Pat hol., 1 8 : 389- 394.

Henry , J. Eo, E. A. Oma , and J. A. Onsager. 1978. Relative e ffe ~ tive n e ss of ulv spr ay appli cations of spores of No sema l o custae again st grasshoppers. J. Econ. Entomol., 71 :629-632.

Henry , J . E . 1981. Natural and applied control of insects by P rot o zo a ~ Ann. Rev. Entomol ., 26:57-71. Henry, J. E. and J . A. On sager. 1982. Large-scale test of cont r ol of gras shoppers on rangeland with Nosema locustae. J o Econ . Entomol., 75-31-35.

Hewitt , G. B. 1977. Review of forage losses caused by rangeland grasshoppers. U.S. Dept. of Agric. Miscellaneous Publ . No. 1348, 24 pp.

Hewit t, G. B. 19 79 . Hatching and development of rangeland grassho ppers in relation to forage growth, temperature and precipitation. Environ. Entomol., 8:24-29. Hirst, J . M. and 0. J. Stedma n. 1963 e Dry liberation of f ungus spores by r a indrops. J . Gen. Mi~robiol. 33:335-344. Hsiao, T. c. 1973. Plant r esponses to water stress. Ann. Rev. Plant Physiol., 24:519-570 . Hutchison, J. A. 1963. The genus Entomophthora in the western hemisphere . Trans. Kansas Acad. Sci., 66:237-254. Ignoffo , c. M., C. Garcia, D. L . Hostetter, and R. E. Pinnell. 1977. Vertical movement of conidia of Nomuraea rileyi through s a nd and loam soils. J. Econ. Ent., 70:163-164 . .Isely, D. 1942. Ins ect problems resulting from changes in agriculture in Arkansas. J. Econ . Ent. , 35:473-477.

Kahn, J. 1964. Patang a ou tbreak in Thailand in 1963. Typescript 6 pp . 43

Kalmakoff, T. and J. R. Miles. 1980. Ecological approaches to the use of microbial pathogens in insect control. Bioscience , 30:344-348.

Kantack, B. 1981. South Dakota farmers bit by hoppers. S . Dak. State Univ. Collegian, Sept. 2, p. 7.

Lefebvre, C~ L. 1934 . Penetration and development of the fungus, Beauv er~a bassiana, in the tissues of the corn borer. Ann . Botany 48:441-452.

MacBain Cameron, J. W. 1963. Factors affecting the use of microbial pathogens in insect control. Ann. Rev. Entomol., 8:265-286.

Mackie , D. B. 1923. The Philippine locust (Pachytylus migratoroides , R. and R.): natural influences affecting its propagation and distribution. Philippine Agr . Rev., 6:538-547. f.facLeod, D. M. 1956. Notes on the genus Etnpu·sa Cohn. Can. J. Bot. 34:16-25. ·

MacLeod, D. M. 1963 . Entomophthorales infections. In " Insect Pathology , An Advanced Treatise", (E. A.­ Steinhaus, ed.), 2 :189-231. Academic Press, New York and London. 689 pp.

MacLeod , D. M. , and E. Muller-Kegler. 1973. Entomogenous fungi: Entomophthora species with pear-shaped to almost spher1cal conidia (Enthomophthorales: Enthomophthora ceae). Mycologia, 65:823-884.

MacLeod, D. M. , David Tyrrell, and Mary A. Welton. 1980. Isolation a nd growt h of the grasshopper pathogen, Entomophthora g ryl l i. J. Invertbre. Path. 36:85--89.

Madelin , M. F. 1963. Diseases caused by hypomycetous fungi . In, "Insect Pa thology, --An Advanced Treatise", (E. A. Steinhaus , ed. ), 2:233-271. Academic Press, New York and London . 689 pp.

McGinnis, R. J. 1959. Grasshopper-man's worst natural e nemy. Sci. Di gest, 45:8-22.

McMartin, A. 1 935. The South African locust fungus. Exp. sta. s. African Sugar ~ Assoc., Mt. Edgecombe~ 44

Milner, R. J . 1978. Note of the occurrence of Enthornopht hora grylli, a fungal pathogen of grasshoppe r s in Australia. J. Aust. Ent. Soc., 17:293-296 .

Nelson, D. , W. D. Valovage, and R. D. Frye. 1982. Infection of grasshoppers with Ent·omophaga (=Entomophthora) gry lli by injection of germinating resting spores. J. Invertebr. Pathol., 39:416-418. Onsager, Jw A. 1977. Comparison of five methods for esti mating density of rangeland grasshoppers. J. Econ. Ent., 70:187-190.

Onsager , J. A. , and G. B. Hewitt. 1982. Rangeland grasshoppers: average longevity and daily rate of mortality among six species in nature. Environ. Entornol., 11:127-133. Parker, J. R. 1930. Some effects of temperature and moisture upon Melan·oplus mexic·anus Saussure and Carnnula pe·11ucida Scudder () . Mont. Agr1c. Exp. Sta. Bull. 223.

Parker, J. R. , and R. L. Shotwell. 1932. Devastation of a large area by the differential and the two-striped grasshoppers. J. Econ. Ent., 25:174-187. Pepper, J. H. 1955. The ecological approach to management of inse ct populations. J. Econ. Ent., 48:451-456. Petkov, P. 1939. Die bekampfung der heuschrecken mit Empusa. Int. Congr. Entornol. (1938) 4:2616-2618. Pfadt , R. E. 1949. Range grasshoppers as an economic factor i n the production of livestock. Wyo. Range Manageme nt, No. 7. 7 pp. Pickford, R. 1966. Development, survival, and reproduction of Carnnula pellucida (Scudder) (Orthoptera:Acrididae) in relat1on t o cl1matic conditions. Canad. Entomol., 98 :158-169. Pickford, R., and P. W. Riegert. 1964. The fungus disease caused by Entomophthora grylli Fres., and its effects on grasshopper populations in Saskatchewan in 1963. Canad. Entomol., 96-1158-1166. 45

Prasertphon, S. and Y. Tanada. 1 968. The formation and c irculatio n, in Galleria, of hypha! bodies of Entomophthor a c eous fungi. J. Invertebr. Pathol., 11:260-280.

Rao , Y. R., and M. C. Che rian. 1940. Control of the rice grasshopper- !. I ndian Farming (Delhi), 1:433-436.

Riddle , L. W. 1 906. On the cytology of the . Contribution from the Cryto­ gamic Laboratory o f Harvard Univ., 63:177-197.

Riege rt, P. 1968 . A history of grasshopper abundance surveys a nd forecast of outbreaks in Saskatchewan. Memiors Ent. Soc. Can. No. 52.

Rockwood, L. P. 195 0. Entomogenous fungi of the family Entomophthoraceae in the pacific northwest. J. Econ. Ent., 43: 704-707. Radel , c. F. 1977 . A grasshopper model for a grassland e c o system. Eco l ogy , 58:227-245.

Roffey, J. 1968. The occurrence -of the fungus Entomopht h·o·ra g·ryl.l i Fres. -on locusts and grasshoppers i n tha~la nd. J. Invertebr. Pathol., 11:237-241.

Samsin a kova, A. , S. Misikova , and J. Leopold. 1971. Action of enzymatic systems of Beauveria bass·i ·ana on the cutic l e · o f the greater wax moth larvae · ("Ga·l ·le·r ·ia me l lonella). J. Invertebr. Pathol., 18:322-330. Sanderson, M. w. 1939. Crop replacement in relation to grasshopper abundan ce ~ J. Econ. Ent., 32:484-486. Sawyer, w. H. 1 933 . . The development of Entom·oph·tho·ra s p haer·o sperma upon Rhopobo·ta vacc · ~ ·nl. · a·na. Ann. Bo tany, 47 : 799-811. Schaefer, E . E. 1936. The white fungus disease (Beauveria bas siana) amo ng red l ocusts in South Africa and some obs e r v ations on the grey fungus disease · (Ernpusa gry lli) • Union of S . Africa Sci. Bull. No. 160. scoggan , A. c. and M. A. Brusven. 1973. Grasshopper-plant community associations in Idaho in relation t o t he natural and a ltered environment. Melanderia, 11 :22-32.

Severin, H. c. and G. I. Gilbertson. 1917. Grasshoppers and their control. S . Dak. Agric. Exp. Sta. Bull. 1 72. 46

Shotwell, R. L. 1 941 . Life histories of grasshoppers on the Great Plains. USDA Tech. Bull. 774.

Skaife, S. H. 1925. The locust fungus Ernpusa grylli, and i ts effects on its host. s. Afr1can J. Sci., 22:298-308.

Slansky, F . and P. Feeny. 1977. Stabilization of the rate of nitrogen accumulation by larvae of the cabbage butterfly on wild and cultivated food plants. Ecol. Monogr., 47:209-228. Srnee, c. 1936. Notes on the red locust (Nornadacris septernfasciata) in Nyasaland 1933-34. Bull. Entomol. Res., 27:15-35.

Smith, L. B. 1969 . Possible effects of change in the environment on grasshopper populations. Manitoba Ent., 3:51-55 .

Smith, R. J . , S . Pekrul , E. A. Grula. 1981. Requirement for sequential enzymatic activities for penetration of the integuement of the corn earworrn (Heliothis zea) . J. Invertebr. Pathol., 38:335-344.

Soper, R., D. M. MacLeod. 1981. Descriptive epizootiology of an a phid mycosis. U.S. Dept. of Agriculture, Tech . Bull . No. 1631, 17 pp.

Soper, R. 1 980. Personal communication. Boyce Thompson Inst itute, Ithaca, New York.

Spawn, G. B. 19 45. Tillage methods in grasshopper control. s. Dak. Agric . Exp. Sta. Bull. 379. Steinhaus, E. A. 1949. Principles of insect pathology. McGraw-Hill Book Co., New York, Toronto, and London. 757 pp. Steinhaus , E. A. (ed.) 1963. Insect Pathology, An Advanced Treatise. Vol. 2. Academic Press, New York and London, 689 pp. Sweetman, H. L. 1963. The principles of biological control. wm. c. Brown Co., Dubquer Iowa. 560 pp. Tanada, Y. 1959. Microbial control of insect pest. Ann. Rev. Entomol., 4:277-302. 47

Thaxter, R. 1 8 88. The Entomophthoraceae of the United States. Memoirs Bos. Soc. Nat. Hist., 4:133-201.

Treher n e, R. C. and E. R. Buckell. 1924. Grasshoppers of British Columbia. Canada. Dept. Agric., 39:1-45.

Ullyett , G. C. and D. B. Schonken. 1940. A fungus disease of Plutella mac ulip~rtnis Curt. in South Africa, with not es on the use of entomogenous fungi in insect control. Union of S. Africa Dept. Agric. Forest.; Sci. Bull., 218:1-24. Uvarov, D. 1956. (1958). Recent trends and needs of Acridological research~ Proc. lOth Int. Congr. Ent., 3:6 9-74.

Walton , R. R. and F e A. Fenton. 1939. Notes on Empusa grylli in Ok lahoma. J. Econ. Ent., 32:155-156. 48

APPENDICES 49

Appendix A

Cropland and Rangeland Grasshopper Species of South Dakota Ageneotettix deorum

Amphitornus coloradus

Aulocara e lliotti

Camnula pellucida

Eritettix simplex Melanoplus bivittatus Melanoplus differentialis

Melanoplus femurrubrum Melanoplus packardii Melanoplus sanguinipes

Phoetaliotes nebrascensis

Trachyrachys kiowa 50

Appendix B

Destructive Rangeland Grasshopper Species Of The Great Plains (Hewitt, 1977) Aerope dellus clavatus (Thomas)

Ageneotettix deorum (Scudder)

Amphitornus c oloradus (Thomas)

Aulocara ell i o tti (Thomas)

Boopedo n nubilum (Say) Camnula pelluci da (Scudder)

Chorthippus curtipennis (Harris) Cordillacris spp .

Drepanopterna femoraturn (Scudder)

Encoptolophus sordidus costalis (Scudder)

Eritettix simplex (Scudder) Melanoplus infantilis (Scudder) Melanoplus packardii (Scudder) Melanoplus sanguinipes (F.)

Mermiria spp.

Morseiella flaviventr~s (Bruner) Opeia obscura (Thomas) Phlibostroma quadrimaculatum (Thomas) Phoetaloites nebrascensis (Thomas)

Psoloessa spp. Trachyrhachys kiowa (Thomas) Trimerotropis pal.lidpennis (Burmeister) 51

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