Root injury and midsummer adult abundance of clover root curculio (CRC), Sitona hispidulus (Fabricius), was surveyed in 24 different aged southeastern Minnesota alfalfa fields. CRC presence was not detected in first year fields 2-3 months following stand establishment. Increased root scarring was observed as stand age increased and most fields 3-5 years old showed heavy CRC root scarring. High CRC adult popUlations and widespread root scarring was found in second year alfalfa fields which suggests that CRC is a mobile insect capable of rapidly colonizing new plantings

Cranshaw, Whitney S

English

Valparaiso University

The Great Lakes Entomologist Volume 18 Number 2 - Summer 1985 Number 2 - Summer 1985 Article 5 June 1985 Clover Root Curculio Injury and Abundance in Minnesota Alfalfa of Different Stand Age Whitney S. Cranshaw Colorado State University Follow this and additional works at: https://scholar.valpo.edu/tgle  Part of the Entomology Commons Recommended Citation Cranshaw, Whitney S. 1985. "Clover Root Curculio Injury and Abundance in Minnesota Alfalfa of Different Stand Age," The Great Lakes Entomologist, vol 18 (2) Available at: https://scholar.valpo.edu/tgle/vol18/iss2/5 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. CLOVER ROOT CURCULIO INJURY AND ABUNDANCE IN MINNESOTA ALFALFA OF DIFFERENT STAND AGE Whitney S. Cranshaw] ABSTRACT Root injury and midsummer adult abundance of clover root curculio (CRC), Sitona hispidulus (Fabricius), was surveyed in 24 different aged southeastern Minnesota alfalfa fields. CRC presence was not detected in first year fields 2-3 months following stand establishment. Increased root scarring was observed as stand age increased and most fields 3-5 years old showed heavy CRC root scarring. High CRC adult popUlations and widespread root scarring was found in second year alfalfa fields which suggests that CRC is a mobile insect capable of rapidly colonizing new plantings. The clover root curculio (CRC), Sitona hispidulus (Fabricius), is a common insect of Minnesota alfalfa (Radcliffe et al. 1976). Larval stages can damage the crop by feeding on underground parts of the plant (Wildermuth 1910) and may directly cause reductions in plant vigor and yield. Feeding wounds also can allow entrance and establishment of pathogens (Dickason et al. 1968). Eggs are laid after adults move back into fields following a summer aestivation period along field edges. The insect has been reported to be a weak flier (Bigger 1930) although Prescott and Newton (1963) and Pausch et al. (1980) reported that flights occur during warm days in late summer and early autumn. Prescott and Newton concluded that pedestrian travel might be most important for infestation f adjacent fields whereas winged migration was important in colonizing distant fields. If CRC movement is largely restricted to walking, colonization and injury might be expected to occur slowly after stand establishment. CRC populations and injury would be expected to build more quickly in later years s both "native" and additional immigrants oviposited within a field. This pattern would be reflected in the larval damage of different aged alfalfa stands. This study was conducted to determine the rapidity of CRC coloni­zation of new alfalfa stands and to survey the extent of larval injury to alfalfa roots. METHODS AND MATERIALS During July 1983, surveys were made of CRC abundance and root injury in 24 southeastern Minnesota alfalfa fields. Fields were of various stand ages and were all established in mid spring plantings. Alfalfa roots were rated for weevil scarring on a scale of 1 (no scarring) to 10 (100% surface area root scarring). Adult CRC were collected twice, 8 July and 18-20 July, by taking a 25-sweep sample from the field interior. The timing of these surveys was made to coincide with the period of peak adult Sitona spp. abundance found by Radcliffe et al. (1976). Because of recent harvest, seven fields could not be sampled on the latter date. None of the fields had had any insecticide applications made to them while in alfalfa. IDepartment of Entomology, Colorado State University, Fort Collins, CO 80524. 1Cranshaw: Clover Root Curculio Injury and Abundance in Minnesota Alfalfa ofPublished by ValpoScholar, 198594 THE GREAT LAKES ENTOMOLOGIST Vo!. 18, No.2 Table 1. Sitona hispidulus mid-summer adult populations and larval root injury found in southeastern Minnesota alfalfa fields of different stand ages, 1983. S. hispidulus/25 sweepsa Root damage ratingb Planting date No. fields x(Range) No. fields x (Range) 1983 3 0 3 1.0 (1.0) 1982 4 17.8 (4-31) 11 4.1 (2.3-5.0) 1981 4 11.0 (1-18) 5 5.9 (4.3-6.5) 1980 1.0 8.3 (8.3) 1979 3 1.3 (1-2) 4 8.0 (7.2-9.0) ·Sweep net samples taken 18-20 July; no adults were collected on 8 July. bSurvey root damage rating on a 1 (no scarring) to ]0 (100% root surface area scarring). RESULTS AND DISCUSSION CRC root scarring increased in severity with stand age (Table 1). Fields planted during spring 1983 were not observed to have roots injured by CRC weevil larvae, which is consistent with the finding of Lieber et al. (1981) that dispersal to new fields occurs in late fall. CRC damage was widespread in second year alfalfa and 3-4-year-old stands planted in 1979-1980 were heavily damaged. The rapidity with which fields were invaded suggests S. hispidulus may be quite mobile. The pattern of increasing larval injury with stand age was expected since root scarring accumulates over years. The severe root scarring found in older alfalfa stands further supports suggestions that CRC injury may be more important in Minnesota than is generally recognized (Radcliffe et at 1976). No CRC adults were collected from the first year alfalfa fields or in any fields during the 8 July survey. However, during 18-20 July sampling high CRC populations were found in fields 1-2 years after planting. This pattern further confirms that CRC is sufficiently dispersive to rapidly colonize new plantings in Minnesota. Lower adult populations were indicated in older fields, 3-4 years after planting. Apparently CRC populations do not necessarily continue to increase in Minnesota alfalfa with time. possibly because of the activity of natural controls (Turner 1957). After the stand establishment year, population build-up of CRC can be rapid and may be followed by a population leveling or even a decline. ACKNOWLEDGMENTS I gratefully appreciate the efforts of John Skoglund and Arney Imholt of Steuart and Armstrong Consulting, Inc. for assistance in collecting samples for this study. LITERATURE CITED Bigger, J. G. 1930. Notes on the life history of he clover root curculio, Sitona hispidula (Fab.) in central Illinois. 1. Econ. Entomo!. 23:234-241. Dickason, E. A., C. M. Leach, and A. E. Gross. 1968. Clover root curculio injury and vascular decay of alfalfa roots. J. Econ. Entomo!. 61:1163-1168. 2The Great Lakes Entomologist, Vol. 18, No. 2 [1985], Art. 5https://scholar.valpo.edu/tgle/vol18/iss2/51985 THE GREAT LAKES ENTOMOLOGIST 95 Pausch, R. D., S. J. Roberts, R. J. Barney, and E. I. Armbrust. 1980. Localized field migration of the adult alfalfa weevil, clover leaf weevil, and clover root curculio (Coleoptera: Curculionidae), and its implication for a fall pest management program. Great Lakes Entomol. 13:195-200. Lieber, G. ., B. C. Pass, and K. V. Yeargan. 1981. Seasonal abundance and activity of Sitona hispidulus adults in Kentucky. Environ. Entomol. 10:27-30. Prescott, H. W. and R. C. Newton. 1963. Flight study of the clover root curculio. I. Econ. Entomol. 56:368-370. Radcliffe, E. B., R. W. Weires, R. E Stucker, and D. K. Barnes. 1976. InfluenCe ofcultivars and pesticides on pea aphid, spotted alfalfa aphid, and associated arthropod taxa in Minnesota alfalfa ecosystems. Environ. Entomol. 5: 1195-1207. Turner, E. C. If. 1957. Control of the clover root curculio in alfalfa. 50:645-648. Wildermuth, V. L. 1910. The clover root curculio, Sitones hispidulus Fab. USDA Bur. Entomol. and Plant Quar. 85(part 1II):29-38. 3Cranshaw: Clover Root Curculio Injury and Abundance in Minnesota Alfalfa ofPublished by ValpoScholar, 1985

Clover Root Curculio Injury and Abundance in Minnesota Alfalfa of Different Stand Age

ValpoScholar

The Great Lakes Entomologist 
Volume 18 
Number 2 - Summer 1985 Number 2 - Summer 
1985 
Article 5 
June 1985 
Clover Root Curculio Injury and Abundance in Minnesota Alfalfa of 
Different Stand Age 
Whitney S. Cranshaw 
Colorado State University 
Follow this and additional works at: https://scholar.valpo.edu/tgle 
 Part of the Entomology Commons 
Recommended Citation 
Cranshaw, Whitney S. 1985. "Clover Root Curculio Injury and Abundance in Minnesota Alfalfa of Different 
Stand Age," The Great Lakes Entomologist, vol 18 (2) 
Available at: https://scholar.valpo.edu/tgle/vol18/iss2/5 
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. 
CLOVER ROOT CURCULIO INJURY AND ABUNDANCE IN 

MINNESOTA ALFALFA OF DIFFERENT STAND AGE 

Whitney S. Cranshaw] 
ABSTRACT 
Root injury and midsummer adult abundance of clover root curculio (CRC), Sitona 
hispidulus (Fabricius), was surveyed in 24 different aged southeastern Minnesota alfalfa 
fields. CRC presence was not detected in first year fields 2-3 months following stand 
establishment. Increased root scarring was observed as stand age increased and most fields 
3-5 
years old showed heavy CRC root scarring. High CRC adult popUlations and 
widespread root scarring was found in second year alfalfa fields which suggests that CRC is 
a mobile insect capable 
of rapidly colonizing new plantings. 
The clover root curculio (CRC), Sitona hispidulus (Fabricius), is a common insect of 
Minnesota alfalfa (Radcliffe et al. 1976). Larval stages can damage the crop by feeding 
on underground parts of the plant (Wildermuth 1910) and may directly cause reductions 
in plant vigor and yield. Feeding wounds also can allow entrance and establishment of 
pathogens (Dickason et al. 1968). 
Eggs are laid after adults move back into fields following a summer aestivation period 
along field edges. The insect has been reported to be a weak flier (Bigger 1930) although 
Prescott and Newton (1963) and Pausch et al. (1980) reported that flights occur during 
warm days in late summer and early autumn. Prescott and Newton concluded that 
pedestrian travel might be most important for infestation f adjacent fields whereas winged 
migration was important in colonizing distant fields. 
If 
CRC movement 
is largely restricted to walking, colonization and injury might be 
expected to occur slowly after stand establishment. CRC populations and injury would be 
expected to build more quickly in later years s both "native" and additional immigrants 
oviposited within a field. This pattern would be reflected in the larval damage of different 
aged alfalfa stands. This study was conducted to determine the rapidity of CRC coloni­
zation of new alfalfa stands and to survey the extent of larval injury to alfalfa roots. 
METHODS AND MATERIALS 
During July 1983, surveys were made of CRC abundance and root injury in 24 
southeastern Minnesota alfalfa fields. Fields were of various stand ages and were all 
established in mid spring plantings. Alfalfa roots were rated for weevil scarring on a scale 
of 
1 (no scarring) 
to 10 (100% surface area root scarring). Adult CRC were collected 
twice, 8 July and 18-20 July, by taking a 25-sweep sample from the field interior. The 
timing of these surveys was made to coincide with the period of peak adult Sitona spp. 
abundance found by Radcliffe et al. (1976). Because of recent harvest, seven fields could 
not be sampled on the latter date. None of the fields had had any insecticide applications 
made to them while in alfalfa. 
IDepartment of Entomology, Colorado State University, Fort Collins, CO 80524. 
1
Cranshaw: Clover Root Curculio Injury and Abundance in Minnesota Alfalfa of
Published by ValpoScholar, 1985
94 THE GREAT LAKES ENTOMOLOGIST Vo!. 18, No.2 
Table 1. Sitona hispidulus mid-summer adult populations and larval root injury found in 
southeastern Minnesota alfalfa fields of different stand ages, 1983. 
S. hispidulus/25 sweepsa Root damage ratingb 
Planting date No. fields x(Range) No. fields x (Range) 
1983 3 0 3 1.0 (1.0) 
1982 4 17.8 (4-31) 11 4.1 (2.3-5.0) 
1981 4 11.0 (1-18) 5 5.9 (4.3-6.5) 
1980 1.0 8.3 (8.3) 
1979 3 1.3 (1-2) 4 8.0 (7.2-9.0) 
·Sweep net samples taken 18-20 July; no adults were collected on 8 July. 

bS
urvey root damage rating on a 
1 (no scarring) to ]0 (100% root surface area scarring). 

RESULTS AND DISCUSSION 
CRC root scarring increased in severity with stand age (Table 1). Fields planted during 
spring 1983 were not observed to have roots injured by CRC weevil larvae, which is 
consistent with the finding of Lieber et al. (1981) that dispersal to new fields occurs in late 
fall. CRC damage was widespread in second year alfalfa and 3-4-year-old stands planted 
in 
1979-1980 were heavily damaged. The rapidity with which fields were invaded 
suggests 
S. hispidulus may be quite mobile. The pattern of increasing larval injury with 
stand age was expected since root scarring accumulates over years. The severe root 
scarring found in older alfalfa stands further supports suggestions that CRC injury may be 
more important in Minnesota than is generally recognized (Radcliffe et at 1976). 
No 
CRC adults were collected from the first year alfalfa fields or in any fields during 
the 8 July survey. However, during 18-20 July sampling high CRC populations were 
found 
in fields 1-2 years after planting. This pattern further confirms that CRC is 
sufficiently dispersive to rapidly colonize new plantings in Minnesota. Lower adult 
populations were indicated in older fields, 3-4 years after planting. Apparently CRC 
populations do not necessarily continue to increase in Minnesota alfalfa with time. 
possibly because of the activity of natural controls (Turner 1957). After the stand 
establishment year, population build-up of CRC can be rapid and may be followed by a 
population leveling or even a decline. 
ACKNOWLEDGMENTS 
I gratefully appreciate the efforts of John Skoglund and Arney Imholt of Steuart and 
Armstrong Consulting, Inc. for assistance in collecting samples for this study. 
LITERATURE CITED 
Bigger, J. G. 1930. Notes on the life history of he clover root curculio, Sitona hispidula 
(Fab.) in central Illinois. 1. Econ. Entomo!. 23:234-241. 
Dickason, E. A., C. M. Leach, and A. E. Gross. 1968. Clover root curculio injury and 
vascular decay of alfalfa roots. J. Econ. Entomo!. 61:1163-1168. 
2
The Great Lakes Entomologist, Vol. 18, No. 2 [1985], Art. 5
https://scholar.valpo.edu/tgle/vol18/iss2/5
1985 THE GREAT LAKES ENTOMOLOGIST 95 
Pausch, R. D., S. J. Roberts, R. J. Barney, and E. I. Armbrust. 1980. Localized field 
migration of the adult alfalfa weevil, clover leaf weevil, and clover root curculio 
(Coleoptera: Curculionidae), and its implication for a fall pest management program. 
Great Lakes Entomol. 13:195-200. 
Lieber, G. ., B. C. Pass, and K. V. Yeargan. 1981. Seasonal abundance and activity of 
Sitona hispidulus adults in Kentucky. Environ. Entomol. 10:27-30. 
Prescott, H. W. and R. C. Newton. 1963. Flight study of the clover root curculio. I. Econ. 
Entomol. 56:368-370. 
Radcliffe, E. B., R. W. Weires, R. E Stucker, and D. K. Barnes. 1976. InfluenCe of
cultivars and pesticides on pea aphid, spotted alfalfa aphid, and associated arthropod 
taxa in Minnesota alfalfa ecosystems. Environ. Entomol. 5: 1195-1207. 
Turner, E. C. If. 1957. Control of the clover root curculio in alfalfa. 50:645-648. 
Wildermuth, V. L. 1910. The clover root curculio, Sitones hispidulus Fab. USDA Bur. 
Entomol. and Plant Quar. 85(part 1II):29-38. 
3
Cranshaw: Clover Root Curculio Injury and Abundance in Minnesota Alfalfa of
Published by ValpoScholar, 1985


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Clover Root Curculio Injury and Abundance in Minnesota Alfalfa of Different Stand Age

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