Fumigation Of Citrus Trees

In this case, the tree to be fumigated with the hydrocyanic acid gas is covered with an octagonal sheet tent (Fig. 1325) made of six and one-half ounce special drill or eight-ounce special army duck, and the gas is generated in the ordinary way beneath it. The tent is so marked that when in position it is an easy matter to determine the distance over the tent and the circumference at the ground. When these figures are known, the proper dosage may be obtained from the following chart, which has been prepared for a strength of one ounce of cyanide for each 100 cubic feet of space:

DISTANCE AROUND, IN FEET.

DISTANCE OVERt IN FEET.

16

18

20

22

24

26

28

30

32

34

36

38

40

42

44

46

48

50

52

54

56

58

60

62

64

66

68

10

2

2

2

2

2

10

12

2

2

3

3

3

3

12

14

3

3

3

3

3

3

4

4

4

4

4

5

14

16

3

3

3

3

4

4

4

4

4

5

5

5

5

5

16

18

3

3

3

4

4

4

5

5

5

5

5

5

5

6

18

20

22

24

26

28

30

32

34

36

38

40

42

44

46

48

50

52

54

56

58

60

62

64

66

68

20

3

4

4

5

5

5

5

5

5

6

6

6

7

7

8

9

20

22

5

5

5

5

5

5

6

6

7

7

8

8

8

9

22

24

5

5

5

6

6

6

7

8

8

8

8

9

9

24

26

5

6

6

7

7

8

8

8

9

9

10

10

10

11

11

11

26

28

6

7

8

8

8

8

9

9

I0

11

11

11

11

12

12

28

30

32

34

36

38

40

42

44

46

48

50

52

54

56

58

60

62

64

66

68

30

7

8

8

8

9

9

10

10

11

11

11

11

12

13

14

14

14

15

16

16

30

32

9

10

10

11

11

12

12

12

13

13

14

14

14

15

16

16

17

32

34

10

11

11

12

13

13

14

14

14

14

15

16

16

17

17

17

34

36

11

11

12

13

13

14

14

15

15

16

17

17

17

17

18

19

36

38

12

12

13

14

14

15

16

16

17

17

17

18

18

19

20

38

40

42

44

46

48

50

52

54

56

58

60

62

64

66

68

40

12

13

14

14

15

15

16

17

17

18

18

19

20

20

20

40

41

14

14

15

15

16

17

17

18

18

19

20

20

20

21

41

42

15

15

16

17

17

18

19

19

20

20

20

21

21

42

43

16

17

17

18

19

19

20

20

20

20

21

22

43

44

17

18

19

19

20

20

20

21

22

22

44

50

52

54

56

58

60

62

64

66

68

45

17

18

19

20

20

20

21

22

23

23

45

46

18

19

20

20

20

21

22

22

23

23

46

47

18

19

20

20

21

22

22

23

23

24

47

46

19

20

20

21

22

22

23

23

24

24

48

49

19

20

21

21

22

23

23

23

24

25

49

Dosage chart for fumigating citrus trees with high-grade sodium cyanide (Bureau of Entomology, United States Department of Agriculture).

The top line of numbers, beginning at 16 and continuing to 68, represents the distance in feet around the bottom of the tent. The outer vertical columns of larger numbers running from 10 to 49 represent the distance in feet over the top of the tent. The number of ounces of cyanide to use for a tree of known dimensions is found in that square where the vertical column headed by the distance around the tree intersects the horizontal line of figures corresponding to the distance over. For certain insects it is not advisable to use the full dosage schedule.

Sodium cyanide (NaCN) is coming into use as a substitute for potassium cyanide. When pure, this compound contains 53 per cent of cyanogen; that is, about 33 per cent more of cyanogen than is present in potassium cyanide. It is customary to indicate the strength of sodium cyanide in terms of potassium cyanide; that is, pure sodium cyanide is said to be 133 per cent pure. This means that 100 pounds of sodium cyanide will yield as much cyanogen as 133 pounds of potassium cyanide. For fumigation purposes, sodium cyanide should be at least 124 per cent pure and should not contain more than 1 per cent of common salt.

Because of the greater content of cyanogen of sodium cyanide, a smaller quantity is required. The chemicals should be combined in the following proportions: Sodium cyanide, one ounce; sulfuric acid, one and one-half fluid ounces; water, two ounces.

The following dosage schedule corresponds to the one given above for potassium cyanide:

16

18

20

22

24

26

28

30

32

34

36

38

40

42

44

46

48

50

52

54

56

58

60

62

64

66

68

70

72

74

76

78

10

1

1

1

1/2

1 1/2

10

12

1 1/2

I 1/2

1 1/2

1 1/2

2

2

2 1/2

12

14

1 1/2

2

2

2 1/2

2 1/2

2 1/2

3

3

3/2

4

4 1/2

5

14

16

2

2 1/2

2/2

3

3

3

3 1/2

3 1/2

4

4/2

5

5 1/2

6

7

16

18

3

3

3 1/2

3 1/2

4

4 1/2

4 1/2

5 1/2

5 1/2

6

7

7 1/2

8

18

20

22

24.

26

28

30

32

34

36

38

40

42

44

46

48

50

52

54

56

58

60

62

64

66

68

70

72

74

76

78

20

3

4

4 1/2

5

5 1/2

5 1/2

6

6 1/2

7

7

8

8 1/2

9

9 1/2

20

22

4 1/2

5

5 1/2

6

6 1//2

7

7 1/2

7 1/2

8

8 1/2

8 1/2

9 1/2

10

10 1/2

22

24

5 1/2

6 1/2

7

7 1/2

8

8 1/2

9 1/2

9 1/2

9 1/2

10

10 1/2

11

11 1/2

12

24

26

7

8

8 1/2

9

9/2

10

10 1/2

10 1/2

11

11

11 1/2

12

13

14

I4 1/2

15

26

28

8 1/2

9/2

10

101/2

11

11 1/2

11 1/2

12 1/2

12 1/2

13

13 1/2

14

14 1/2

15 1/2

16

28

30

32

34

36

38

40

42

44

46

48

50

52

54

56

58

60

62

64

66

68

70

7Z

74

76

78

30

10

11

11 1/2

12

12 1/2

13

13 1/2

14

14 1/2

I4 1/2

15

15 1/2

16 1/2

17 1/2

18

19

20

20 1/2

21 1/2

30

32

12

12 1/2

13

14

15

15 1/2

16

16 1/2

17

17 1/2

18

18 1/2

19

19 1/2

20 1/2

21 1/2

22 1/2

32

34

13

14

15

16

17

17 1/2:

18

181/2

19

19 1/2

20

20 1/2

21

21 1/2

22 1/2

23

34

36

14

15

I6

17

17 1/2

18

19 1/2

20

20 1/2

21 1/2

21 1/2

22

22 1/2

23

23 1/2

25 1/2

36

38

16

16 1/2

17 1/2

18 1/2

19

20 1/2

21

21 1/2

22

23

23 1/2

24

24 1/2

25

25 1/2

38

40

42

44

46

48

50

52

54

56

58

60

62

64

66

68

70

72

74

76

78

40

17

18

19

20

21

22

22 1/2

23

24

24 1/2

25

25 1/2

26

26 1/2

27

27 1/2

28

40

41

18

19

20

21

22

22 1/2

23 1/2

24

24 1/2

25

25 1/2

26

26 1/2

27

27 1/2

28

28 1/2

29

41

42

20

20 1/2

22

22 1/2

23

24 1/2

25

25 1/2

26

26 1/2

27

2714

28

28

29

29

30

30 1/2

42

43

21 1/2

22 1/2

23

23 1/2

25

25 1/2

26

26 1/2

27

27 1/2

28

28 1/2

29

29 1/2

30

30 1/2

31

43

44

23

23 1/2

24

25

26

26 1/2

27

27 1/2

28

28 1/2

29

29 1/2

30

31

31 1/2

32

44

30

52

54

56

58

60

62

64

66

68

70

72

74

76

78

45

24

25

26

26 1/2

27

27 1/2

28

2.9

29

30

30 1/2

31

31 1/2

32

33

45

46

24 1/2

25 1/2

26 1/2

27 1/2

27 1/2

28

28 1/2

29 1/2

30

30 1/2

2:

31 1/2

32 1/2

33

34

46

47

25

26

27

27 1/2

28

28 1/2

29

30

30 1/2

31 1/2

32

32 1/2

33

34

35

47

48

25 1/2

26 1/2

27 1/2

28

2 9 1/2.

29

29 1/2

30 1/2

31

32

32 1/2

33

34

35

36

46

49

26 1/2

21

28

28 1/2

29

29 1/2

30

31

31 1/2

32 1/2

33

34

35

36

37

49

50

52

54

56

58

60

62

64

66

68

70

72

74

76

78

50

30

31

31 1/2

32 1/2

33

33 1/2

35

36

37

38

50

51

31

31 1/2

32

33

33 1/2

34

36

37

30

39

51

52

31/ 1/2

32

33

33 1/2

34

35

37

38

39

41

52

53

32

32 1/2

33 1/2

34

35

36

38

39

40

41

53

54

32 1/2

33

34

35

36

37

39

40

41

42

54

60

62

64

66

68

70

72

74

76

78

55

33

34

35

36

37

37 1/2

40

41

42

43

55

56

34

35

36

37

37 1/2

38

40 1/2

42

43

44

56

57

34 1/2

35 1/2

36 1/2

37 1/2

38 1/2

39

41

42 1/2

43 1/2

45

57

58

35

36

37

38

39

40

42

43

44

46

58

59

36

36 1/2

38

39

40

40 1/2

42 1/2

43 1/2

45

47

59

Dosage chart for fumigating citrus trees with potassium cyanide (Bureau of Entomology, United States Department of Agriculture).

Nicotine Preparations

Tobacco is used in various ways in fumigating greenhouses. For smoking or smudging greenhouses, tobacco-stems are burned slowly. Best results are secured when a sheet-iron vessel made for the purpose is used, having holes in the bottom to supply draft. A quart of live coals is placed in the bottom of the vessel, and about a pailful of tobacco-stems is laid on them. The stems should not blaze, but burn with a slow smudge. If they are slightly damp, better results are obtained. Some plants are injured by a very heavy smoke, and in order to avoid this injury, and also more effectually to destroy the insects, it is better to smoke rather lightly and often. It is always well to smoke through two consecutive days, for the insects which persist through the first treatment, being weak, will be killed by the second.

A fumigating tent (Morrill system).

Fig. 1325. A fumigating tent (Morrill system).

If the plants are wet, the smoke is more likely to scorch them. The smudge often injures flowers, as those of roses and chrysanthemums. In order to avoid this injury, the flowers should be covered with paper bags. Violet plants are very liable to injury.

Tobacco fumes can be more conveniently generated by burning strips of prepared nicotine paper, or by vaporizing a concentrated aqueous solution of nicotine over alcohol or special kerosene lamps.

Bisulfid of carbon is a thin liquid that volatilizes at a very low temperature, the vapor being very destructive to animal life. It is exceedingly inflammable, and should never be used near a lamp or fire. It is sometimes used for the control of certain root insects. It is poured into holes made around the infested plants, and these are then immediately closed up causing the fumes to permeate the soil in all directions.

Against weevils infesting stored grain and seeds, carbon bisulfid is effective at the rate of five to eight pounds for each 1,000 cubic feet, provided the application is made while the temperature is not below 65° F. Make the bins as tight as possible. If bins are only single sheathed with common flooring use twenty to twenty-five pounds carbon bisulfid. Let the fumigation continue for at least twenty-four hours. Care should be taken not to apply carbon bisulfied when there is indication of heating in the grain. C. R. Crosby.

Robert Matheson.