Rapid field release of adult parasitoids sprayed with the nucleopolyhedrosis virus of the European pine sawfly successfully transferred the virus to feeding larval colonies

Coppel, H. C

Hall, D. J

Mohamed, M. A

Podgwaite, J. D

English

Valparaiso University

The Great Lakes Entomologist Volume 14 Number 4 - Winter 1981 Number 4 - Winter 1981 Article 2 December 1981 Field Release of Virus-Sprayed Adult Parasitoids of the European Pine Sawfly (Hymenoptera: Diprionidae) in Wisconsin M. A. Mohamed University of Wisconsin H. C. Coppel University of Wisconsin D. J. Hall Wisconsin Department of Natural Resources J. D. Podgwaite Northeastern Forest Experiment Station Follow this and additional works at: https://scholar.valpo.edu/tgle  Part of the Entomology Commons Recommended Citation Mohamed, M. A.; Coppel, H. C.; Hall, D. J.; and Podgwaite, J. D. 1981. "Field Release of Virus-Sprayed Adult Parasitoids of the European Pine Sawfly (Hymenoptera: Diprionidae) in Wisconsin," The Great Lakes Entomologist, vol 14 (4) Available at: https://scholar.valpo.edu/tgle/vol14/iss4/2 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. 1981 THE GREAT LAKES ENTOMOLOGIST 177 FIELD RELEASE OF VIRUS-SPRAYED ADULT PARASITOIDS OF THE EUROPEAN PINE SAWFLY (HYMENOPTERA: DIPRIONIDAE) IN WISCONSIN I M. A. Mohamed 2, H. C. Coppel2, D. J. Hall 3 and J. D. Podgwaite 4 ABSTRACT Rapid field release of adult parasitoids sprayed with the nucleopolyhedrosis virus of the European pine sawfly successfully transferred the virus to feeding larval colonies. Laboratory studies by Thompson and Steinhaus (1950) showed that the parasitoid Apanteles medicaginis (Muesebeck) could mechanically vector the virus ofthe alfalfa cater­pillar Colias eurytheme Boisduval. Infection occurred primarily as a result of stinging with the contaminated ovipositor; however it was also suggested that body contamination of the parasitoids could spread the virus over the food plant of the pest. These same authors showed that when ants were fed on virus-filled larval cadavers and allowed to walk over uncontaminated plants, the latter became infectious when fed to healthy larvae. Stairs (1976) reported on virus dispersion and indicated that certain parasitoids playa key role in the development of epizootics because they vector the virus efficiently. He used the sarco­phagid parasitoid, Sarcophaga aldrichi (Parker) to illustrate his point. These adult parasitoids are attracted to recently virus-killed larvae of the forest tent caterpillar, Malacosoma dis­stria (Hubner) and feed on them. Their bodies become contaminated and the virus is trans­ferred to foliage later consumed by the host larvae. The intensity of the epizootics varied directly with the population levels of the adult parasites. Our field study is corroborative with the observations of Stairs (1976) except that we used the ichneumonid parasitoid, Lophyroplectus oblongopunctatus (Hartig), recently introduced and established in Wisconsin against the European pine sawfly, Neodiprion sertifer (Geoffroy) (Kraemer et aL 1979). We herein report the experimental manipulation of virus-sprayed parasitoids for pest suppression. MATERIALS AND METHODS Larvae of the European pine sawfly were collected in 1980 from the site where L. ob­longopunctatus was released in 1977 (Kraemer et al. 1979). These were reared by Hall to the cocoon stage in 10# paper bags provided with foliage. Adult sawflies emerged in the fall of 1980 and those cocoons from which no sawflies emerged were stored at refrigerator temper­ature (4cC) during the winter months. The overwintered cocoons were placed in incubation (room temperature 21°C) during mid-April. Male and female parasitoids were observed mating in the cages. We divided the parasitoids into two groups, each consisting of ca 100 individuals in a 2:1 ratio f females to males. One group was left untreated whereas the 1 Research supported by the College of Agriculturnl and Life Sciences, University of Wisconsin, Madison, in part by the Wisconsin Department of Naturnl Resources through the School of Natural Resources. and in part through a cooperative study (#4500-FS-NE-2202.77) with the Forest Service of the CSDA. 2 Department of Entomology. University of Wisconsin, Madison, WI 53706. 3 Wisconsin Department of Natul'al Resources, Madison, WI 53706. 4 Northeastem Forest Experiment Station. Hamden, CT 06514. 1Mohamed et al.: Field Release of Virus-Sprayed Adult Parasitoids of the EuropeanPublished by ValpoScholar, 1981178 	 THE GREAT LAKES ENTOMOLOGIST Vol. 14, N .4 second group was treated with virus while in the emergence cage. The parasitoids were sprayed with 10 ml aliquots of an aqueous suspension of the nucleopolyhedrosis virus at a concentration of 2.6 x 10 7 polyhedral inclusion bodies (PIB) per milliIitre. A chromist atomizer was utilized. The adults were sprayed three times with a 15 min drying period between sprays. The two groups were then transferred for release in the field. We selected two plantations of red pine, Pinus resinosa Ait., where second instar N. sertifer larvae predominated. The densities were relatively high at 3-10 colonies per tree. Both plantations were monitored one week prior to parasitoid release. This consisted of searching for visual evidence of virus infected larvae as well as sampling apparently healthy larvae. Healthy larvae were macerated in the laboratory and examined for PIB by brightfield microscopy at 6OOX, After parasitoid release the plantations were monitored weekly for three weeks to detect diseased or dead larvae. Approximately 50 trees within a 9O-m radius from the point of parasitoid release were examined in each plot. Dead larvae, suspected of being virus-killed. were stored singly in sterile plastic dispos­able test tubes and examined in the laboratory as previously described. Two subsamples were taken at random from each larval colony which showed some mortality. RESULTS AND DISCUSSION We found no evidence of virus presence in either plantation prior to parasitoid release. Direct observations immediately following ield releases showed considerable activity by the female parasitoids in and around the larval colonies. The larvae in the plantation where virus-free parasitoids were released gave no indication of nucleopolyhedrosis infection up to 21 days whereas the plantation where virus-sprayed adults were released showed 0.4% mortality from virus infection after 14 days. After 21 days the mortality rose to 2%. Dead larvae were in instars 4 to 6 and upon examination for PIB had an average of 5 x 10 4 PIB/larva after 14 days and 2.13 x 10 6 PIB/larva after 21 days. Though the percentage mortality was low, the numbers of virus-sprayed adults released was also low. Thus the idea of introducing a virus by means of a parasitoid vector was amply demonstrated. Such a strategy does not entail large investments and ensures some measure of dispersal with the potential of reaching locations inaccessible to mist blowers or other power equipment (Franz 1964). Because the parasitoid's presence is marked by diseased colonies one could use such data to measure its dispersal capacity as well as its microhabitat preference. Such information would be of considerable value in a classical biological control program. ACKNOWLEDGMENTS The authors gratefully acknowledge the technical assistance of Odette Mohamed. LITERATURE CITED Franz, J. M. 1964. Microorganisms in the biological control of insects. p. 256-266 in Starr, M. P. (ed.) Global impacts of applied microbiology. John Wiley and Sons, New York. Kraemer, M. E., H. C. Coppel, and D. J. Hall. 1979. The establishment of Lophy,.oplectus luteator, a larval pardsitoid of the European pine sawfly Neodip,.ion sertifer in Wisconsin. Univ. Wisconsin For. Res. Note #225. 3 p. Stairs, G. R. 1%7. Quantitative aspects of virus dispersion and the development of epizoo­tics in insect populations p. 19-23 in Proceedings f the Joint United States-Japan Seminar on microbial control of insect pests. Shukosha Printing Co. Fukuoka. Thompson, 	C. G. and E. A. Steinhaus. 1950. Further tests using a polyhedrosis virus to control the alfalfa caterpillar. Hilgardia 19:411-445. 2The Great Lakes Entomologist, Vol. 14, No. 4 [1981], Art. 2https://scholar.valpo.edu/tgle/vol14/iss4/2

Field Release of Virus-Sprayed Adult Parasitoids of the European Pine Sawfly (Hymenoptera: Diprionidae) in Wisconsin

ValpoScholar

The Great Lakes Entomologist 
Volume 14 
Number 4 - Winter 1981 Number 4 - Winter 
1981 
Article 2 
December 1981 
Field Release of Virus-Sprayed Adult Parasitoids of the European 
Pine Sawfly (Hymenoptera: Diprionidae) in Wisconsin 
M. A. Mohamed 
University of Wisconsin 
H. C. Coppel 
University of Wisconsin 
D. J. Hall 
Wisconsin Department of Natural Resources 
J. D. Podgwaite 
Northeastern Forest Experiment Station 
Follow this and additional works at: https://scholar.valpo.edu/tgle 
 Part of the Entomology Commons 
Recommended Citation 
Mohamed, M. A.; Coppel, H. C.; Hall, D. J.; and Podgwaite, J. D. 1981. "Field Release of Virus-Sprayed Adult 
Parasitoids of the European Pine Sawfly (Hymenoptera: Diprionidae) in Wisconsin," The Great Lakes 
Entomologist, vol 14 (4) 
Available at: https://scholar.valpo.edu/tgle/vol14/iss4/2 
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. 
1981 THE GREAT LAKES ENTOMOLOGIST 177 
FIELD RELEASE OF VIRUS-SPRAYED ADULT 
PARASITOIDS OF THE EUROPEAN PINE SAWFLY 
(HYMENOPTERA: DIPRIONIDAE) IN WISCONSIN I 
M. A. Mohamed 2, H. C. Coppel2, 
D. J. Hall 3 and J. D. Podgwaite 4 
ABSTRACT 
Rapid field release of adult parasitoids sprayed with the nucleopolyhedrosis virus of the 
European 
pine sawfly successfully transferred the virus to feeding larval colonies. 
Laboratory studies by Thompson and Steinhaus 
(1950) showed that the parasitoid 
Apanteles medicaginis (Muesebeck) could mechanically vector the virus ofthe alfalfa cater­
pillar Colias eurytheme Boisduval. Infection occurred primarily as a result of stinging with 
the contaminated ovipositor; however it was also suggested that body contamination of the 
parasitoids could spread the virus over the food plant of the pest. These same authors 
showed that when ants were fed on virus-filled larval cadavers and allowed to walk over 
uncontaminated plants, the latter became infectious when fed to healthy larvae. Stairs (1976) 
reported on virus dispersion and indicated that certain parasitoids playa key role in the 
development of epizootics because they vector the virus efficiently. He used the sarco­
phagid parasitoid, Sarcophaga aldrichi (Parker) to illustrate his point. These adult parasitoids 
are 
attracted to recently virus-killed larvae 
of the forest tent caterpillar, Malacosoma dis­
stria (Hubner) and feed on them. Their bodies become contaminated and the virus is trans­
ferred to foliage later consumed by the host larvae. The intensity of the epizootics varied 
directly with the population levels of the adult parasites. Our field study is corroborative 
with the observations of Stairs (1976) except that we used the ichneumonid parasitoid, 
Lophyroplectus oblongopunctatus (Hartig), recently introduced and established in 
Wisconsin against the European pine sawfly, Neodiprion sertifer (Geoffroy) (Kraemer et aL 
1979). We herein report the experimental manipulation of virus-sprayed parasitoids for pest 
suppression. 
MATERIALS AND METHODS 
Larvae of 
the European pine sawfly were collected 
in 1980 from the site where L. ob­
longopunctatus was released in 1977 (Kraemer et al. 1979). These were reared by Hall to the 
cocoon 
stage in 10# paper bags provided with foliage. Adult sawflies emerged in the fall 
of 
1980 and those cocoons from which no sawflies emerged were stored at refrigerator temper­
ature (4cC) during the winter months. The overwintered cocoons were placed in incubation 
(room temperature 21°C) during mid-April. Male and female parasitoids were observed 
mating in the cages. We divided the parasitoids into two groups, each consisting of ca 100 
individuals in a 2:1 ratio f females to males. One group was left untreated whereas the 
1 Research supported by the College of Agriculturnl and Life Sciences, University of Wisconsin, 
Madison, in part by the Wisconsin Department of Naturnl Resources through the School of Natural 
Resources. and in part through a cooperative study (#4500-FS-NE-2202.77) with the Forest Service of 
the CSDA. 
2 Department of Entomology. University of Wisconsin, Madison, WI 53706. 
3 Wisconsin Department of Natul'al Resources, Madison, WI 53706. 
4 Northeastem Forest Experiment Station. Hamden, CT 06514. 
1
Mohamed et al.: Field Release of Virus-Sprayed Adult Parasitoids of the European
Published by ValpoScholar, 1981
178 	 THE GREAT LAKES ENTOMOLOGIST Vol. 14, N .4 
second 
group was treated with virus while in the emergence cage. The parasitoids were 
sprayed 
with 
10 ml aliquots of an aqueous suspension of the nucleopolyhedrosis virus at a 
concentration of 
2.6 x 
10 7 polyhedral inclusion bodies (PIB) per milliIitre. A chromist 
atomizer 
was utilized. The adults were sprayed three times with a 
15 min drying period 
between 
sprays. The 
two groups were then transferred for release in the field. 
We 
selected two plantations 
of red pine, Pinus resinosa Ait., where second instar N. 
sertifer larvae predominated. The densities were relatively high at 3-10 colonies per tree. 
Both 
plantations were monitored one week prior to parasitoid release. This consisted 
of 
searching for visual evidence of virus infected larvae as well as sampling apparently healthy 
larvae. Healthy larvae were macerated in the laboratory and examined for PIB by brightfield 
microscopy at 6OOX, After parasitoid release the plantations were monitored weekly for 
three weeks to 
detect diseased 
or dead larvae. Approximately 50 trees within a 9O-m radius 
from the point of parasitoid release were examined in each plot. 
Dead 
larvae, suspected 
of being virus-killed. were stored singly in sterile plastic dispos­
able test tubes and examined in the laboratory as previously described. Two subsamples 
were taken at 
random from each larval colony which showed some mortality. 
RESULTS 
AND DISCUSSION 
We 
found 
no evidence of virus presence in either plantation prior to parasitoid release. 
Direct 
observations immediately following ield releases showed considerable activity by 
the female parasitoids in and around the larval colonies. The larvae 
in the plantation where 
virus-free parasitoids were released gave no indication of nucleopolyhedrosis infection up to 
21 
days whereas the plantation where virus-sprayed adults were released showed 0.4% 
mortality from virus infection after 
14 days. After 21 days the mortality rose to 2%. Dead 
larvae were in instars 4 to 6 and upon examination for PIB had an average of 5 x 10 4 
PIB/larva 
after 
14 days and 2.13 x 10 6 PIB/larva after 21 days. 
Though the percentage mortality was low, the numbers of virus-sprayed adults released 
was also low. Thus the idea of introducing a virus by means of a parasitoid vector was amply 
demonstrated. 
Such a strategy does not entail large investments and ensures some measure of 
dispersal with the potential 
of reaching locations inaccessible to mist blowers or other 
power 
equipment (Franz 
1964). Because the parasitoid's presence is marked by diseased 
colonies one could use such data to measure its dispersal capacity as well as its microhabitat 
preference. Such information would be of considerable value in a classical biological control 
program. 
ACKNOWLEDGMENTS 
The authors 
gratefully acknowledge the technical assistance 
of Odette Mohamed. 
LITERATURE CITED 
Franz, J. 
M. 1964. Microorganisms in the biological control 
of insects. p. 256-266 in Starr, 
M. P. (ed.) Global impacts of applied microbiology. John Wiley and Sons, New York. 
Kraemer, 
M. 
E., H. C. Coppel, and D. J. Hall. 1979. The establishment of Lophy,.oplectus 
luteator, a larval pardsitoid of the European pine sawfly Neodip,.ion sertifer in Wisconsin. 
Univ. Wisconsin For. Res. Note #225. 3 p. 
Stairs, G. R. 1%7. Quantitative aspects of virus dispersion and the development of epizoo­
tics in insect populations p. 19-23 in Proceedings f the Joint United States-Japan Seminar 
on 
microbial control 
of insect pests. Shukosha Printing Co. Fukuoka. 
Thompson, 	
C. 
G. and E. A. Steinhaus. 1950. Further tests using a polyhedrosis virus to 
control the 
alfalfa caterpillar. Hilgardia 19:411-445. 
2
The Great Lakes Entomologist, Vol. 14, No. 4 [1981], Art. 2
https://scholar.valpo.edu/tgle/vol14/iss4/2


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Field Release of Virus-Sprayed Adult Parasitoids of the European Pine Sawfly (Hymenoptera: Diprionidae) in Wisconsin

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