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Assefa Gebre-Amlak
Colorado State University Extension
Greeley, CO 80631-2049
Phone: (970) 304-6535 Ext. 2074
Fax: (970) 351-0415
E-mail: Assefa.Gebre-Amlak@Colostate.Edu


 
Home > Degree Days > Alfalfa Weevil

Alfalfa Weevil


Alfalfa Weevil
Estimation of the weevil instars present in the field can be calculated using degree-days. Alfalfa weevil development increases at a nearly constant rate as the temperature rises above 48°F (9°C.). The amount of warm weather required for weevil larvae to complete development is measured in units of degree-days. For the alfalfa weevil, degree-days are accumulated after 1 March for each 24-hour period in which temperatures exceed 48°F (10°C). Using this technique sampling should begin when 148 degree days have accumulated.  Weather stations in MT and WY are included at http://ippc2.orst.edu/wea/  that is linked to a degree day calculator. This timing coincides with the peak occurrence of second instars.  In years of unusually warm or cold springs, weevil development may occur earlier or later than normal. The alfalfa weevil population relative to the estimated date of first harvest may influence management choices. Third and fourth larval instars cause most of the economic damage, so initiating sampling at the peak occurrence of second instars should provide adequate sampling prior to economic weevil populations.

 1. Begin accumulating degree-days on March 1 or when temperature first exceeds 48° F. (the developmental threshold)

Degree-days = Maximum temp. + Minimum temp. – 48 F
                                                   2 
2. Add each day's accumulation to the previous total.
3. Compare the running total to the degree-days that correspond with recommendations for initiation of sampling.

2011 Degree-Days Accumulated (ADD)

 

Date

 

Akron

 

Burlington

East Adams

 

Greeley

 

Kirk

 

Haxtun

 

Wray

3/1/11

0.00

0.00

0.00

0.00

0.00

0.00

0.00

3/2/11

0.00

0.00

0.00

0.00

0.00

0.00

0.00

3/3/11

0.00

0.00

0.00

0.00

0.00

0.00

0.00

3/4/11

0.00

0.00

0.00

0.00

0.00

0.00

0.00

3/5/11

0.00

0.00

0.00

0.00

0.00

0.00

0.00

3/6/11

0.00

0.00

0.00

0.00

0.00

0.00

0.00

3/7/11

0.00

0.00

0.00

0.00

0.00

0.00

0.00

3/8/11

0.00

0.00

0.00

0.00

0.00

0.00

0.00

3/9/11

0.00

0.00

0.00

0.00

0.00

0.00

0.00

3/10/11

0.00

0.00

0.00

0.00

0.00

0.00

0.00

3/11/11

0.00

0.35

0.00

0.00

2.15

0.00

0.00

3/12/11

0.00

0.35

0.00

0.00

2.15

0.00

0.00

3/13/11

0.00

0.35

0.00

0.00

2.15

0.00

0.00

3/14/11

0.00

0.35

0.00

0.00

2.15

0.00

0.00

3/15/11

0.00

0.35

0.00

0.00

2.15

0.00

0.00

3/16/11

5.60

7.80

7.55

2.20

5.95

0.25

4.00

3/17/11

5.60

7.80

7.55

4.45

5.95

0.25

4.35

3/18/11

5.60

7.80

7.55

4.45

5.95

0.25

4.35

3/19/11

12.55

15.25

13.75

6.75

13.95

0.25

12.95

3/20/11

14.90

22.70

16.05

6.75

19.10

1.55

16.25

3/21/11

22.05

33.05

26.50

11.25

24.85

1.55

22.75

3/22/11

22.05

33.05

26.50

13.95

24.85

1.55

22.75

3/23/11

22.05

33.05

26.50

13.95

24.85

1.55

22.75

3/24/11

22.05

33.05

26.50

13.95

24.85

1.55

22.75

3/25/11

22.05

33.05

26.50

13.95

24.85

1.55

22.75

3/26/11

22.05

33.05

26.50

13.95

24.85

1.55

22.75

3/27/11

22.05

33.05

26.50

13.95

24.85

1.55

22.75

3/28/11

22.05

33.05

26.50

13.95

24.85

1.55

22.75

3/29/11

22.05

33.05

26.50

13.95

24.85

1.55

22.75

3/30/11

22.05

33.05

26.50

13.95

24.85

1.55

22.75

3/31/11

22.05

34.20

31.85

18.55

26.75

1.55

22.75

4/1/11

22.05

34.85

31.95

23.05

27.25

1.90

23.60

4/2/11

32.75

48.25

48.05

32.60

38.70

11.15

33.80

4/3/11

32.75

48.25

48.05

32.60

38.70

11.15

33.80

4/4/11

32.75

48.25

48.05

32.60

38.70

11.15

33.80

4/5/11

37.20

48.25

55.70

37.35

44.60

14.95

33.80

4/6/11

37.20

48.30

55.70

37.35

44.60

14.95

34.45

4/7/11

38.15

51.70

57.35

37.70

48.10

14.95

37.40

4/8/11

44.45

64.20

66.85

46.45

56.90

22.40

45.85

4/9/11

50.75

79.30

76.65

52.70

68.65

30.30

55.75

4/10/11

50.75

79.30

76.65

52.70

68.65

30.30

55.75

4/11/11

50.75

79.30

76.65

52.70

76.20

30.35

58.55

4/12/11

50.75

86.45

77.85

52.70

76.20

30.35

60.95

4/13/11

50.75

88.50

77.85

52.70

77.65

30.35

63.30

4/14/11

50.75

88.50

77.85

52.70

77.65

30.35

63.30

4/15/11

50.75

88.50

77.85

52.70

77.65

30.35

63.30

4/16/08

50.75

88.50

77.85

52.70

77.65

30.35

63.30

4//17/11

57.35

94.15

77.85

57.15

84.25

36.15

68.40

4/18/11

57.35

94.15

84.45

60.30

85.15

36.15

68.40

4/19/11

57.35

94.15

84.45

60.30

85.15

36.15

68.40

4/20/11

57.35

94.15

84.45

60.30

85.15

36.15

68.40

4/21/11

60.70

96.75

84.45

64.25

88.45

38.85

68.40

4/22/11

60.70

99.00

85.10

64.55

90.15

39.30

69.75

4/23/11

60.70

99.00

85.10

64.55

90.15

39.30

69.75

4/24/11

60.70

99.00

85.10

64.55

90.15

39.30

69.75

4/25/11

60.70

99.00

85.10

64.55

90.15

39.30

69.75

4/26/11

60.70

99.00

85.10

64.55

90.15

39.30

70.30

4/27/11

60.70

99.00

85.10

64.55

90.15

39.30

70.30

4/28/11

61.05

100.55

86.90

65.65

93.35

39.50

74.95

4/29/11

67.80

111.10

94.85

67.35

102.00

45.10

84.60

4/30/11

59.00

111.10

94.85

67.35

102.00

45.10

84.60

5/1/11

59.00

111.10

94.85

67.35

102.00

45.10

84.60

5/2/11

59.00

111.10

94.85

67.35

102.00

45.10

84.60

5/3/11

59.80

112.60

98.00

67.35

103.65

45.10

87.70

5/4/11

59.80

117.30

98.00

67.35

106.50

45.10

90.10

5/5/11

60.50

118.85

98.50

68.20

108.35

45.50

93.80

5/6/11

73.85

134.25

113.30

75.85

123.10

55.40

107.05

5/7/11

86.20

149.20

130.15

90.95

135.40

68.20

119.90

5/8/11

104.00

172.35

151.75

104.85

154.80

83.95

139.40

5/9/11

122.40

194.00

151.75

120.50

154.80

99.85

158.70

5/10/11

130.65

206.95

151.75

127.70

154.80

99.85

158.70

5/11/11

130.65

214.35

151.75

127.70

160.10

99.85

165.35

 

 

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