A microsporidium species, not previously reported, was found infecting field populations of the alfalfa weevil, Hypera postica, in Illinois. The pathogen is widely distributed thoughout the state. Percent infection ranged from 1 % to 50% at different collection locations. Characteristics of the microsporidium and possible modes of transmission are presented

Armbrust, Edward J

Maddox, Joseph V

Roberts, Stephen J

Solter, Leellen F

English

Valparaiso University

The Great Lakes Entomologist Volume 26 Number 2 - Summer 1993 Number 2 - Summer 1993 Article 7 June 1993 A New Microsporidium in Alfalfa Weevil Populations: Distribution and Characterization Leellen F. Solter Illinois Natural History Survey Stephen J. Roberts Illinois Natural History Survey Joseph V. Maddox Illinois Natural History Survey Edward J. Armbrust Illinois Natural History Survey Follow this and additional works at: https://scholar.valpo.edu/tgle  Part of the Entomology Commons Recommended Citation Solter, Leellen F.; Roberts, Stephen J.; Maddox, Joseph V.; and Armbrust, Edward J. 1993. "A New Microsporidium in Alfalfa Weevil Populations: Distribution and Characterization," The Great Lakes Entomologist, vol 26 (2) Available at: https://scholar.valpo.edu/tgle/vol26/iss2/7 This Peer-Review Article is brought to you for free and open access by the Department of Biology at ValpoScholar. It has been accepted for inclusion in The Great Lakes Entomologist by an authorized administrator of ValpoScholar. For more information, please contact a ValpoScholar staff member at scholar@valpo.edu. 1993 THE GREAT LAKES ENTOMOLOGIST 151 A NEW MICROSPORIDIUM IN ALFALFA WEEVIL POPULATIONS: DISTRIBUTION AND CHARACTERIZATION Leellen F, Solter', Stephen J. Roberts1 Joseph V. Maddoxl and Edward J. Armbrust] ABSTRACT A microsporidium species, not previously reported, was found infecting field populations of he alfalfa weevil, Hypera postica, in Illinois. The patho­gen is widely distributed thoughout the state. Percent infection ranged from 1 % to 50% at different collection locations. Characteristics of the microspori­dium and possible modes of transmission are presented. Prior to this report, three different microsporidia were recovered from the alfalfa weevil, Hypera postica (Gyllenhal). A microsporidium, thought to be a Nosema species, was isolated from a single dead alfalfa weevil larva collected in Edwards County, Illinois (Maddox and Luckman 1966). Although we have Giemsa-stained slides of this micro sporidium, viable spores are not presently available. Drea et al. (1969) reported a microsporidium (Nosema sp.) infecting a laboratory colony f alfalfa weevils in Moorestown, New Jersey. W  have both Giemsa-stained slides and viable spores of this microsporidium. A third microsporidium was recovered from a laboratory colony of alfalfa weevils at Utah State University and described as Perezia hyperae (Youssef 1974). Later, Sprague (1977) placed P. hyperae in the genus Nosema. The micro sporidium species isolated by Maddox and Luckmann (1966) is distinctly different from the other two species based on comparisons of Giemsa-stained slides. In 1974 alfalfa weevil larvae from the Illinois counties of Washington and Mason were examined for pathogens (Roberts e  al., 1977). Three of the 715. larvae examined were infected with a microsporidium considered to be cons:pe­cific with the Nosema species recovered in 1966. Because this Nosema specIes has been observed in alfalfa weevil populations only two times, and in both cases the prevalence was very low « 1%), we believe it is possible that the alfalfa weevil is not the primary host for this microsporidium. The Nosema species reported by Drea et al. (1969) and Youssef (1974) have never been reported from field collections of alfalfa weevils. We conducted a statewide survey for alfalfa weevil pathogens in April of 1990. A micro sporidium, different from the descriptions of the previously reported species, was found. This organism was recovered from alfalfa fields in 22 of 31 counties surveyed from 1990 through 1992 (Figure 1). It was also found in a col nr of field-collected alfalfa weevils at Ohio State University, in a field sample 0 alfalfa weevils collected on burr clover and black medic near Lutcher, Louisiana, and in field samples of alfalfa from Prince Georges Co., Maryland and Lincoln Co., Missouri. Field-collections in Illinois have shown lCenter for Economic Entomology, Illinois Natural History Survey, 607 E. Pea­body Drive, Champaign, IL 61801. 1Solter et al.: A New Microsporidium in Alfalfa Weevil Populations: DistributionPublished by ValpoScholar, 1993152 THE GREAT LAKES ENTOMOLOGIST Vol. 26, No.2 2!.i~i 	 County surveyed; no microsporidia found. County surveyed; microsporidia found. Figure 1. Prevalence of a new microsporidium species in Illinois. aPrevalence reported is the highest recorded between two collection years. 2The Great Lakes Entomologist, Vol. 26, No. 2 [1993], Art. 7https://scholar.valpo.edu/tgle/vol26/iss2/71993 153THE GREAT LAKES ENTOMOLOGIST Figure 2. Spores of a new microsporidium species in the midgut tissue of the alfalfa weevil. the prevalence of the microsporidium to be from 1 % to 50% (Figure 1) in counties where it was recovered. We believe that the pathogen is relatively new to Illinois alfalfa weevil populations because it was not found in the extensive pathogen surveys in 1966 and 1974. The spores (Figure 2) and vegetative forms of the microsporidium were found in the midgut, hindgut, fat body, and Malpigbian tubules of alfalfa weevil larvae nd adults, and also in salivary gland tissue in the larvae. The spores ranged in length from 2.3 -3.1 /lm and in width from 0.8 to 1.2 /lm. The average spore length was 2.7 ± 0.2 /lm and the average width was 1.0 ± 0.1 JLm (Table 1). We were able to produce horizontal transmission of the micro sporidium when first-instar alfalfa weevils were fed alfalfa leaves coated with spores at a concentration of 1 X 104 spores/JLl. Infection was found in 11 ofl7larvae (65%) that reached the fourth stadium. Control larvae were free of infection. Addi­tionally, we immersed 32 first- and second-instars for 15 seconds in a spore solution at a concentration of 8.8 X 106 spores/JLl. Nineteen larvae survived, and seven (37%) developed infection. The microsporidium also appeared to be transovarially transmitted. Eggs collected from isolated alfalfa weevil females were surface-sterilized by immer­sion in 10% formaldehyde for 10 minutes and rinsed 3 times in dis lled water. The eggs from each female were held in separate rearing dishes from those of other females and, after oviposition, the females were dissected and squash 3Solter et al.: A New Microsporidium in Alfalfa Weevil Populations: DistributionPublished by ValpoScholar, 1993154 THE GREAT LAKES ENTOMOLOGIST Vol. 26, No.2 Table 1. Comparison of rnicrosporidia recovered from the alfalfa weevil. Species Average Average recovered length (!'ffi) width (!'ffi) Shape ~~1.~7------------s-p~h-er-o~id~alNosema hyperaea 3.1 Nosema sp.b 4.9 2.5 spheroidal Nosema sp.c 6.0 4.5 ovoid Undescribed sp. 2.7 1.0 rod aYoussef (1974), revis d by Sprague (1977). bMaddox and Luckmann (1966). cDrea et aI. (1969). preparations of midgut tissues were examined for infection. Eighteen of 21larvae from 3 infected females were infected; 22 larvae produced by 6 unin­fected females were not infected. Additionally, we surface-sterilized 100 eggs collected at random from a heavily infected laboratory colony. Fifty larvae were retrieved and all were infected. Several noneclosed eggs were immersed in a 10% bleach so ution in order to dissolve the chorions and t  destroy any spores which may have been present on the surface of the eggs. Squash preparations were made of the embryos and were examined microscopically for mfection. The embryonic tis­sue was infected with the microsporidium. Studies on the complete life cycle and the ultrastructural characteristics of this new micro sporidium are being conducted. Until these studies are com­pleted, the generic identity of the new microsporidium cannot be determined. Likewise, the importance of th  microsporidium as a biological control agent cannot be fully evaluated until studies on the host range and effect of the disease on the alfalfa weevil are completed. ACKNOWLEDGMENTS We thank Michael R. Jeffords and Leslie C. Lewis for their comments on an earlier version of this manuscript. This paper is a contribution of the Illinois Natural History Survey and the Illinois Agricultural Experiment Sta­tion, College of Agriculture, University of Illinois at Champaign-Urbana. LITERATURE CITED Droo, J. J., Jr., G. W. Angalet and W. H. Day. 1969. Nosema sp. infecting a laboratory colony of the alfalfa weevil. J. Invertebr. Pathol. 13:303-304. Maddox, J. V. and W. H. Luckmann. 1966. A microsporidian disease of the alfalfa weevil, Hypera postica. J. Invertebr. Pathol. 8:543-544. Roberts, S.J., J. V. Maddox, D. P. Bartell,and E. J. Armbrust. 1977. Disease as a larval mortality factor in alfalfa weevil, Hypera postica (Coieoptera:Curculionidae) popula­tions in Illinois. Great Lakes EntomoL 10:199-200. Sprague, V. 1977. Annotated list of species of microsporidia. Pp. 240-241. In: Bulla, L. A. and T. C. Cheng, eds., Comparative Pathology Volume 2, Systematics of the Microsporidia. Plenum Press, N.Y. Youssef, N. N. 1974. Biology and pathogenicity of the microsporidian Perezia hyperae sp. n., a pathogen of the alfalfa weevil, Hypera postica. J. Invertebr. Pathol. 24:282-292. 4The Great Lakes Entomologist, Vol. 26, No. 2 [1993], Art. 7https://scholar.valpo.edu/tgle/vol26/iss2/7

A New Microsporidium in Alfalfa Weevil Populations: Distribution and Characterization

Leellen F Solter

Stephen J Roberts

Joseph V Maddox

Edward J Armbrust

Crossref

ValpoScholar

The Great Lakes Entomologist 
Volume 26 
Number 2 - Summer 1993 Number 2 - Summer 
1993 
Article 7 
June 1993 
A New Microsporidium in Alfalfa Weevil Populations: Distribution 
and Characterization 
Leellen F. Solter 
Illinois Natural History Survey 
Stephen J. Roberts 
Illinois Natural History Survey 
Joseph V. Maddox 
Illinois Natural History Survey 
Edward J. Armbrust 
Illinois Natural History Survey 
Follow this and additional works at: https://scholar.valpo.edu/tgle 
 Part of the Entomology Commons 
Recommended Citation 
Solter, Leellen F.; Roberts, Stephen J.; Maddox, Joseph V.; and Armbrust, Edward J. 1993. "A New 
Microsporidium in Alfalfa Weevil Populations: Distribution and Characterization," The Great Lakes 
Entomologist, vol 26 (2) 
Available at: https://scholar.valpo.edu/tgle/vol26/iss2/7 
This Peer-Review Article is brought to you for free and open access by the Department of Biology at ValpoScholar. 
It has been accepted for inclusion in The Great Lakes Entomologist by an authorized administrator of ValpoScholar. 
For more information, please contact a ValpoScholar staff member at scholar@valpo.edu. 
1993 THE GREAT LAKES ENTOMOLOGIST 151 
A NEW MICROSPORIDIUM IN ALFALFA WEEVIL POPULATIONS: 

DISTRIBUTION AND CHARACTERIZATION 

Leellen F, Solter
'
, Stephen J. Roberts1 

Joseph V. Maddox
l 
and Edward J. Armbrust] 

ABSTRACT 
A microsporidium species, not previously reported, was found infecting 
field populations of he alfalfa weevil, Hypera postica, in Illinois. The patho­
gen is 
widely 
distributed thoughout the state. Percent infection ranged from 
1 % to 50% at different collection locations. Characteristics of the microspori­
dium and possible modes of transmission are presented. 
Prior to this report, three different microsporidia were recovered from the 
alfalfa weevil, Hypera postica (Gyllenhal). A microsporidium, thought to be a 
Nosema 
species, was isolated from a single 
dead alfalfa weevil larva collected 
in Edwards 
County, Illinois (Maddox and Luckman 1966). Although we have 
Giemsa-stained slides 
of this micro sporidium, viable spores are not presently 
available. Drea et al. (1969) reported a microsporidium (Nosema sp.) infecting 
a laboratory colony f alfalfa weevils in Moorestown, New Jersey. W  have 
both 
Giemsa-stained slides 
and viable spores of this microsporidium. A third 
microsporidium was recovered from a laboratory colony of alfalfa weevils at 
Utah State 
University and described 
as Perezia hyperae (Youssef 1974). Later, 
Sprague (1977) placed P. hyperae in the genus Nosema. The micro sporidium 
species isolated by Maddox and Luckmann (1966) is distinctly different from 
the other 
two species based on comparisons of Giemsa-stained slides. In 
1974 alfalfa weevil 
larvae from the Illinois counties of Washington and 
Mason were examined for pathogens (Roberts e  al., 1977). Three of the 715. 
larvae examined were infected with a microsporidium considered to be cons:pe­
cific with the Nosema species recovered in 1966. Because this Nosema specIes 
has 
been observed in alfalfa weevil populations only two times, 
and in both 
cases the prevalence was very low « 1%), we believe it is possible that the 
alfalfa weevil is not the primary host for this microsporidium. The Nosema 
species reported by Drea et al. (1969) and Youssef (1974) have never been 
reported from field collections of alfalfa weevils. 
We conducted a statewide survey for alfalfa weevil pathogens in April of 
1990. A micro sporidium, different from the descriptions of the previously 
reported 
species, 
was found. This organism was recovered from alfalfa fields 
in 22 of 31 counties surveyed from 1990 through 1992 (Figure 1). It was also 
found in a col nr of field-collected alfalfa weevils at Ohio State University, in 
a field sample 0 alfalfa weevils collected on burr clover and black medic near 
Lutcher, Louisiana, and in field samples of alfalfa from Prince Georges Co., 
Maryland 
and Lincoln Co., Missouri. Field-collections in Illinois have shown 
lCenter for Economic Entomology, Illinois Natural History Survey, 607 E. Pea­
body Drive, Champaign, IL 61801. 
1
Solter et al.: A New Microsporidium in Alfalfa Weevil Populations: Distribution
Published by ValpoScholar, 1993
152 THE GREAT LAKES ENTOMOLOGIST Vol. 26, No.2 
2!.i~i 	 County surveyed; no microsporidia found. 
County surveyed; microsporidia found. 
Figure 1. Prevalence of a new microsporidium species in Illinois. aPrevalence reported is 
the 
highest recorded between two collection years. 
2
The Great Lakes Entomologist, Vol. 26, No. 2 [1993], Art. 7
https://scholar.valpo.edu/tgle/vol26/iss2/7
1993 153THE GREAT LAKES ENTOMOLOGIST 
Figure 2. Spores of a new microsporidium species in the midgut tissue of the alfalfa 
weevil. 
the prevalence of the microsporidium to be from 1 % to 50% (Figure 1) in 
counties where it was recovered. We believe that the pathogen is relatively 
new to Illinois alfalfa weevil populations because it was not found in the 
extensive pathogen surveys in 1966 and 1974. 
The spores (Figure 2) and vegetative forms of the microsporidium were 
found in the midgut, hindgut, fat body, and Malpigbian tubules of alfalfa 
weevil larvae nd adults, and also in salivary gland tissue in the larvae. The 
spores ranged in length from 2.3 -3.1 /lm and in width from 0.8 to 1.2 /lm. The 
average spore length was 2.7 ± 0.2 /lm and the average width was 1.0 ± 0.1 
JLm (Table 1). 
We were able to produce horizontal transmission of the micro sporidium 
when first-instar alfalfa weevils were fed alfalfa leaves coated with spores at a 
concentration of 1 X 104 spores/JLl. Infection was found in 11 ofl7larvae (65%) 
that 
reached 
the fourth stadium. Control larvae were free of infection. Addi­
tionally, we immersed 32 first- and second-instars for 15 seconds in a spore 
solution at a concentration of 8.8 X 106 spores/JLl. Nineteen larvae survived, 
and 
seven 
(37%) developed infection. 
The microsporidium also appeared to be transovarially transmitted. Eggs 
collected from isolated alfalfa weevil females were surface-sterilized by immer­
sion in 10% formaldehyde for 10 minutes and rinsed 3 times in dis lled water. 
The eggs from each female were held in separate rearing dishes from those of 
other females and, after oviposition, the females were dissected and squash 
3
Solter et al.: A New Microsporidium in Alfalfa Weevil Populations: Distribution
Published by ValpoScholar, 1993
154 THE GREAT LAKES ENTOMOLOGIST Vol. 26, No.2 
Table 1. Comparison of rnicrosporidia recovered from the alfalfa weevil. 
Species Average Average 
recovered length (!'ffi) width (!'ffi) Shape 
~~1.~7------------s-p~h-er-o~id~alNosema hyperaea 3.1 
Nosema sp.b 4.9 2.5 spheroidal 
Nosema 
sp.c 6.0 
4.5 ovoid 
Undescribed sp. 2.7 1.0 rod 
aYoussef (1974), revis d by Sprague (1977). 
bMaddox and Luckmann (1966). 
cDrea et aI. (1969). 
preparations of midgut tissues were examined for infection. Eighteen of 21
larvae from 3 infected females were infected; 22 larvae produced by 6 unin­
fected females were not infected. 
Additionally, we surface-sterilized 100 eggs collected at random from a 
heavily infected laboratory colony. Fifty larvae were retrieved and all were 
infected. Several noneclosed eggs were immersed in a 10% bleach so ution in 
order to dissolve the chorions and t  destroy any spores which may have been 
present on the surface of the eggs. Squash preparations were made of the 
embryos and were examined microscopically for mfection. The embryonic tis­
sue was infected with the microsporidium. 
Studies on the complete life cycle and the ultrastructural characteristics 
of this new micro sporidium are being conducted. Until these studies are com­
pleted, the generic identity of the new microsporidium cannot be determined. 
Likewise, the importance of th  microsporidium as a biological control agent 
cannot be fully evaluated until studies on the host range and effect of the 
disease on the alfalfa weevil are completed. 
ACKNOWLEDGMENTS 
We thank Michael R. Jeffords and Leslie C. Lewis for their comments on 
an earlier version of this manuscript. This paper is a contribution of the 
Illinois Natural History Survey and the Illinois Agricultural Experiment Sta­
tion, College of Agriculture, University of Illinois at Champaign-Urbana. 
LITERATURE CITED 
Droo, J. J., Jr., G. W. Angalet and W. H. Day. 1969. Nosema sp. infecting a laboratory 
colony of the alfalfa weevil. J. Invertebr. Pathol. 13:303-304. 
Maddox, J. V. and W. H. Luckmann. 1966. A microsporidian disease of the alfalfa 
weevil, Hypera postica. J. Invertebr. Pathol. 8:543-544. 
Roberts, S.J., J. V. Maddox, D. P. Bartell,and E. J. Armbrust. 1977. Disease as a larval 
mortality factor in alfalfa weevil, Hypera postica (Coieoptera:Curculionidae) popula­
tions in Illinois. Great Lakes EntomoL 10:199-200. 
Sprague, V. 1977. Annotated list of species of microsporidia. Pp. 240-241. In: Bulla, L. 
A. and T. C. Cheng, eds., Comparative Pathology Volume 2, Systematics of the 
Microsporidia. Plenum Press, N.Y. 
Youssef, N. N. 1974. Biology and pathogenicity of the microsporidian Perezia hyperae 
sp. n., a pathogen of the alfalfa weevil, Hypera postica. J. Invertebr. Pathol. 
24:282-292. 
4
The Great Lakes Entomologist, Vol. 26, No. 2 [1993], Art. 7
https://scholar.valpo.edu/tgle/vol26/iss2/7


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A New Microsporidium in Alfalfa Weevil Populations: Distribution and Characterization

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