Hand release of 22 5-year-old white spruce, Picea glauca (Moench) Voss, dramatically increased the amount of defoliation by the yellowheaded spruce sawfly, Pikonema alaskens is . The percent defoliation of the released trees was six times the defoliation in the control trees. A light overstory for young white spruce is suggested as a silvicultural method of reducing defoliation by this sawfly

Kulman, H. M

Morse, B. W

English

Valparaiso University

The Great Lakes Entomologist Volume 17 Number 4 - Winter 1984 Number 4 - Winter 1984 Article 11 December 1984 Effect of White Spruce Release on Subsequent Defoliation by the Yellowheaded Spruce Sawfly, Pikonema Alaskensis (Hymenoptera: Tenthredinidae) B. W. Morse University of Minnesota H. M. Kulman University of Minnesota Follow this and additional works at: https://scholar.valpo.edu/tgle  Part of the Entomology Commons Recommended Citation Morse, B. W. and Kulman, H. M. 1984. "Effect of White Spruce Release on Subsequent Defoliation by the Yellowheaded Spruce Sawfly, Pikonema Alaskensis (Hymenoptera: Tenthredinidae)," The Great Lakes Entomologist, vol 17 (4) Available at: https://scholar.valpo.edu/tgle/vol17/iss4/11 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. 1984 THE GREAT LAKES ENTOMOLOGIST 235 EFFECT OF WHITE SPRUCE RELEASE ON SUBSEQUENT DEFOLIATION BY THE YELLOWHEADED SPRUCE SAWFLY, PIKONEMA ALASKENSIS (HYMENOPTERA: TENTHREDINIDAE) 1 B. W. Morse and H. M. Kulman2 ABSTRACT Hand release of 22 5-year-old white spruce, Picea glauca (Moench) Voss, dramatically increased the amount of defoliation by the yellowheaded spruce sawfly, Pikonema alas­kens is . The percent defoliation of the released trees was six times the defoliation in the control trees. A light overs tory for young white spruce is suggested a  a silvicultural method of reducing defoliation by this sawfly. In north central Minnesota, the yellowheaded spruce sawfly (YHSS), Pikonema alas­kensis (Rohwer), is the most important defoliator of young white spruce, Picea glauca (Moench) Voss, plantations. This univoltine sawfly feeds on the current year's foliage from early June to July, when the larvae drop to the ground to overwinter. Population outbreaks usually occur on south facing slopes before crown closure (Morse and Kulman 1984). In addition, severe defoliation has been observed after mechanical and chemical removal of hardwood overstory. It was the purpose of this study to document the effect o  release on subsequent YHSS-caused defoliation f white spruce. METHODS The study took place in a 1.5-ha, 5-year-old white spruce plantation located in the Chippewa National Forest, Minnesota. Approximately 70% of the trees were overtopped predominately by aspen, Populus spp. There were 3000 to 5000 aspen stems/ha. Fifty spruce trees were selected of the same size and with the same amount of overtop­ping. One half of the trees were randomly selected for treatment in September 1982, and the other half were used as untreated controls. The treatment consisted of cutting all light-competing vegetation within 1.5 m from the spruce. Percent defoliation of the current year's foliage, and terminal shoot length were then recorded. The following August, after the larvae had completed feeding, percent defoliation and terminal shoot length were again measured for both groups. An angular transformation of percent defoliation was performed to stabilize the variance. Student t-tests were used to compare the difference between the groups and years. RESULTS AND DISCUSSION There was little defoliation, less than 0.5%, recorded in 1982 for both groups (Fig. 1). Seven marked trees were not relocated the second year and were dropped from the analysis. In the control group, the average defoliation significantly increased in 1983, indicating a general popUlation buildup (P = 0.018). A dramatic increase of defoliation occurred after the trees were released in the treatment group (P < 0.001). In 1983, there 'Paper #13,970, Scientific Journal Series, Minnesota Agriculture Expe iment Station, Saint Paul. 2Department of Entomology, University of Minnesota, S1. Paul, MN 55108. 1Morse and Kulman: Effect of White Spruce Release on Subsequent Defoliation by the YPublished by ValpoScholar, 1984236 THE GREAT LAKES ENTOMOLOGIST Vol. 17, No.4 DEFOLIATION (percent) 25 ~ -Control .. -Released 20 15 I 10 1982 1983 Fig. 1. Response of yellowheaded spruce sawfly-caused defoliation of plantation white spruce to the release, or removal, of a hardwood overstory in the Fall of 1982. was a six-fold increase of defoliation in the treatment over the control (P < 0.001). Increases of defoliation occurred in 21 out of 22 of the released spruce. Half of the control trees showed an increase of defoliation, while the rest remained the same. White spruce in sunny locations such as roadsides, lakefronts, and pastures, tend to be heavily defoliated by the YHSS (Morse 1982). Observations of adult behavior indicate that it is a sun-loving insect (Bartelt et al. 1982). These observations help explain why defoliation increased following the release of shaded white spruce. Terminal shoot growth did not differ between the two groups in 1983 (P > O.S), yet with only one growing season, no inferences can be made about the effect of this release on growth. It could not be determined whether sawfly-caused defoliation resulted in greater growth loss than that due to overstory suppression. White spruce is considered a shade-tolerant species (Barker 1949), withstanding 30-40% overtopping during the first 10 years after planting (Roe 1955). A recent study showed that south-facing had the highest risk of YHSS-caused defoliation (Morse 1984). From a management point f view, high-risk, south-facing slopes could be left with a light overstory during the period before crown closure to prevent heavy defoliation by the YHSS. ACKNOWLEDGMENT Appreciation is extended to R. J. Bartelt for help with this study and to W. E. Miller for review of the manuscript. Financial support came from the C. K. Blandin Foundation f Grand Rapids, Minnesota. 2The Great Lakes Entomologist, Vol. 17, No. 4 [1984], Art. 11https://scholar.valpo.edu/tgle/vol17/iss4/111984 THE GREAT LAKES ENTOMOLOGIST 237 LITERATU RE CITED Barker, F. S. 1949. A revised tolerance table. J. For. 47:179-18l. Bartelt, R. 1., R. L. Jones, and H. M. Kulman. 1982. Evidence for a multicomponent sex pheromone in the yellowheaded spruce sawfly. J. Chern. Eco!. 8:83-94. Morse, B. W, 1982. Estimating yellowheaded spruce sawfly-caused mortality of planta­tion white spruce using aerial photographs. M.S. Thesis, Univ. Minnesota, St. Paul. 50 p. 1984. Management of the yellowheaded spruce sawfly in white spruce planta­tions, Ph.D. dissert. Univ. Minnesota, St. PauL 84 p. Morse, B. W. and H. M. Kulman. 1984. Plantation white spruce mortality: estimates based on aerial photographs and analysis using a life table format. Canadian J. For. Res. 14:195-200. Roe, E. I. 1955. Forest plantation release: what it is-how to do it. USDA For. Servo Lake States For. Expt. Sta, Misc. Rep. 33. 29 p. 3Morse and Kulman: Effect of White Spruce Release on Subsequent Defoliation by the YPublished by ValpoScholar, 1984

Effect of White Spruce Release on Subsequent Defoliation by the Yellowheaded Spruce Sawfly, Pikonema Alaskensis (Hymenoptera: Tenthredinidae)

ValpoScholar

The Great Lakes Entomologist 
Volume 17 
Number 4 - Winter 1984 Number 4 - Winter 
1984 
Article 11 
December 1984 
Effect of White Spruce Release on Subsequent Defoliation by the 
Yellowheaded Spruce Sawfly, Pikonema Alaskensis 
(Hymenoptera: Tenthredinidae) 
B. W. Morse 
University of Minnesota 
H. M. Kulman 
University of Minnesota 
Follow this and additional works at: https://scholar.valpo.edu/tgle 
 Part of the Entomology Commons 
Recommended Citation 
Morse, B. W. and Kulman, H. M. 1984. "Effect of White Spruce Release on Subsequent Defoliation by the 
Yellowheaded Spruce Sawfly, Pikonema Alaskensis (Hymenoptera: Tenthredinidae)," The Great Lakes 
Entomologist, vol 17 (4) 
Available at: https://scholar.valpo.edu/tgle/vol17/iss4/11 
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. 
1984 THE GREAT LAKES ENTOMOLOGIST 235 
EFFECT OF WHITE SPRUCE RELEASE ON SUBSEQUENT 

DEFOLIATION BY THE YELLOWHEADED SPRUCE SAWFLY, 

PIKONEMA ALASKENSIS (HYMENOPTERA: TENTHREDINIDAE) 1 

B. W. Morse and H. M. Kulman2 
ABSTRACT 
Hand release of 22 5-year-old white spruce, Picea glauca (Moench) Voss, dramatically 
increased the amount of defoliation by the yellowheaded spruce sawfly, Pikonema alas­
kens is . The percent defoliation of the released trees was six times the defoliation in the 
control trees. A light overs tory for young white spruce is suggested a  a silvicultural 
method of reducing defoliation by this sawfly. 
In north central Minnesota, the yellowheaded spruce sawfly (YHSS), Pikonema alas­
kensis (Rohwer), is the most important defoliator of young white spruce, Picea glauca 
(Moench) Voss, plantations. This univoltine sawfly feeds on the current year's foliage 
from early June to July, when the larvae drop to the ground to overwinter. 
Population outbreaks usually occur on south facing slopes before crown closure (Morse 
and Kulman 1984). In addition, severe defoliation has been observed after mechanical and 
chemical removal of hardwood overstory. It was the purpose of this study to document the 
effect o  release on subsequent YHSS-caused defoliation f white spruce. 
METHODS 
The study took place in a 1.5-ha, 5-year-old white spruce plantation located in the 
Chippewa National Forest, Minnesota. Approximately 70% of the trees were overtopped 
predominately by aspen, Populus spp. There were 3000 to 5000 aspen stems/ha. 
Fifty spruce trees were selected of the same size and with the same amount of overtop­
ping. One half of the trees were randomly selected for treatment in September 1982, and 
the other half were used as untreated controls. The treatment consisted of cutting all 
light-competing vegetation within 1.5 m from the spruce. Percent defoliation of the 
current year's foliage, and terminal shoot length were then recorded. 
The following August, after the larvae had completed feeding, percent defoliation and 
terminal shoot length were again measured for both groups. An angular transformation of 
percent defoliation was performed to stabilize the variance. Student t-tests were used to 
compare the difference between the groups and years. 
RESULTS AND DISCUSSION 
There was little defoliation, less than 0.5%, recorded in 1982 for both groups (Fig. 1). 
Seven marked trees were not relocated the second year and were dropped from the 
analysis. In the control group, the average defoliation significantly increased in 1983, 
indicating a general popUlation buildup (P = 0.018). A dramatic increase of defoliation 
occurred after the trees were released in the treatment group (P < 0.001). In 1983, there 
'Paper #13,970, Scientific Journal Series, Minnesota Agriculture Expe iment Station, Saint Paul. 
2Department of Entomology, University of Minnesota, S1. Paul, MN 55108. 
1
Morse and Kulman: Effect of White Spruce Release on Subsequent Defoliation by the Y
Published by ValpoScholar, 1984
236 THE GREAT LAKES ENTOMOLOGIST Vol. 17, No.4 
DEFOLIATION 
(percent) 
25 
~ -Control 
.. -Released 
20 
15 
I 
10 
1982 1983 
Fig. 1. Response of yellowheaded spruce sawfly-caused defoliation of plantation white spruce to the 
release, or removal, of a hardwood overstory in the Fall of 1982. 
was a six-fold increase of defoliation in the treatment over the control (P < 0.001). 
Increases of defoliation occurred in 21 out of 22 of the released spruce. Half of the control 
trees showed an increase of defoliation, while the rest remained the same. 
White spruce in sunny locations such as roadsides, lakefronts, and pastures, tend to be 
heavily defoliated by the YHSS (Morse 1982). Observations of adult behavior indicate 
that it is a sun-loving insect (Bartelt et al. 1982). These observations help explain why 
defoliation increased following the release of shaded white spruce. 
Terminal shoot growth did not differ between the two groups in 1983 (P > O.S), yet 
with only one growing season, no inferences can be made about the effect of this release 
on 
growth. It could not 
be determined whether sawfly-caused defoliation resulted in 
greater growth loss than that due to overstory suppression. White spruce is considered a 
shade-tolerant species (Barker 1949), withstanding 30-40% overtopping during the first 
10 
years after planting (Roe 1955). A recent study showed that south-facing had the 
highest risk 
of YHSS-caused defoliation (Morse 1984). From a management point f 
view, high-risk, south-facing slopes could be left with a light overstory during the period 
before crown closure to prevent heavy defoliation by the YHSS. 
ACKNOWLEDGMENT 
Appreciation is extended to R. J. Bartelt for help with this study and to W. E. Miller for 
review of the manuscript. Financial support came from the C. K. Blandin Foundation f 
Grand Rapids, Minnesota. 
2
The Great Lakes Entomologist, Vol. 17, No. 4 [1984], Art. 11
https://scholar.valpo.edu/tgle/vol17/iss4/11
1984 THE GREAT LAKES ENTOMOLOGIST 237 
LITERATU RE CITED 
Barker, F. S. 1949. A revised tolerance table. J. For. 47:179-18l. 
Bartelt, R. 1., R. L. Jones, and H. M. Kulman. 1982. Evidence for a multicomponent sex 
pheromone in the yellowheaded spruce sawfly. J. Chern. Eco!. 8:83-94. 
Morse, B. W, 1982. Estimating yellowheaded spruce sawfly-caused mortality of planta­
tion white spruce using aerial photographs. M.S. Thesis, Univ. Minnesota, St. Paul. 
50 p. 
1984. Management of the yellowheaded spruce sawfly in white spruce planta­
tions, Ph.D. dissert. Univ. Minnesota, St. PauL 84 p. 
Morse, B. W. and H. M. Kulman. 1984. Plantation white spruce mortality: estimates 
based on aerial photographs and analysis using a life table format. Canadian J. For. 
Res. 14:195-200. 
Roe, E. I. 1955. Forest plantation release: what it is-how to do it. USDA For. Servo 
Lake States For. Expt. Sta, Misc. Rep. 33. 29 p. 
3
Morse and Kulman: Effect of White Spruce Release on Subsequent Defoliation by the Y
Published by ValpoScholar, 1984


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Effect of White Spruce Release on Subsequent Defoliation by the Yellowheaded Spruce Sawfly, Pikonema Alaskensis (Hymenoptera: Tenthredinidae)

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