Schedule S. Fumigation of seeds

Contents - Previous - Next

A number of fumigants may be used for the fumigation of seeds without affecting subsequent germination and growth. However, seed treatments must be conducted carefully. Important points to consider are:

(a) strict adherence to recommended dosages and exposure periods;
(b) avoidance of excessive temperatures;
(c) thorough aeration of the seeds immediately the required period of exposure has been completed.

Repetition of fumigation with methyl bromide should be avoided. The moisture content of the seeds is a critical factor in many instances, especially when methyl bromide is used; the limitations on moisture content are mentioned in the following schedules whenever applicable.

The effect of the more important individual fumigants on seed germination is discussed in Chapter 6. For general reviews on the subject of seed fumigation see King et al (1960), Lindgren end Vincent (1962) and Parkin (1963).

All the following schedules refer to seed in permeable teens and sacks. Bulk fumigation of seed would present special problems.

A. SEEDS OF ALL SPECIES

Great care must be taken to ensure that the seed is dry (at or below normal moisture content for prolonged storage, usually less than 12 percent).

(a) Hydrogen cyanide (HCN)

Under atmospheric pressure: 40g/m for 24h at 10 to 19C; or 32g/m for 24 h at 20C and above. Under sustained vacuum: 40g/m for 3 h at 20C and above.

Do not fumigate at temperatures below 10C. It is better to fumigate at 15C or above. Do not fumigate seed with moisture content above 14 percent. For fumigation of conifers see Richardson and Roth (1968).

(b) Ethylene dichloride/carbon tetrachloride mixture (3:1)

Under atmospheric pressure: 480g/m for 24 h at 20C and above.

(c) Methyl bromide

Under atmospheric pressure: 24g/m for 24 h at 10 to 19C; or 16g/m for 24 h at 20C and above. Under sustained vacuum: 40g/m for 3 h at 20C and above. Especially important that the seed is dry. Repetition of fumigation should be avoided (see text). Fumigation above 25C not advisable.

(d) Carbon disulphide

Under atmospheric pressure: 160g/m for 24 h at 20C and above. Highly flammable.

(e) Phosphine

Phosphine may be used to fumigate a wide range of seeds without impairment of germination. The following schedule should be satisfactory for seed fumigation. 2.5 9 of phosphine (generated by application of an aluminium or magnesium phosphide formulation) per m3.

Period of fumigation should be 7 days at 12 to 15C, 6 days at 16 to 20C, 5 days at 21 to 25C or 4 days at 26C or above. For cottonseed see Schedule P. pare D2.

B. STEM AND BULB EELWORM (Ditvlenchus dipsachi)

Recommendations based on findings of Goodey (1945) and of Lubatti and Smith (1948).

1. SEED OF LUCERNE (ALFALFA)

Methyl bromide

Under atmospheric pressure: 24 h at 12 to 25C, dosage according to following table of suggested c x t products and moisture content of seed:

Moisture content (percent) Concentration x time product (mg h/l)
Less than 10 1 400 - 1 500
10 - 11 1 200 - 1 300
11 - 12 1 000 - 1 100
12 - 14 800 - 900

Treatment above 14 percent moisture content is not recommended.

2. ONION SEED

Methyl bromide

Under atmospheric pressure: 24 h at 10 to 20C, dosage according to following table of suggested c x t products and moisture content of seed:

Moisture content (percent) Concentration x time product (mg h/l)
10 - 11 1 000
11 - 12 900
12 800

Treatment above 12 percent moisture content is not recommended.

Schedule T. Fumigation for controlling rodents and other mammalian pests, snakes, birds, snails, ants' nests, wasps and termites

1. RATS AND MICE IN EMPTY STORAGES AND WAREHOUSES

(a) Hydrogen cyanide (HCN)

To be applied as liquid or from discs. 4C or above. 2 to 4g/m (2 to 4 oz/l 000 ft) for 6 h.

(b) Methyl bromide

0C or above; 4g/m for 5 h.

(c) Chloropicrin

4C or above; 8g/m from 8 to 12 h.

2. RATS AND MICE IN FRUIT STORAGES AND SPACES CONTAINING FOOD

Methyl bromide

1C or above; 4g/m for 4 h. At this c x t methyl bromide does not normally injure susceptible apples and fruit in storage.

3. RATS AND MICE IN SHIP HOLDS, PREFERABLY WHEN EMPTY

(a) Hydrogen cyanide (HCN)

4C or above; 2 to 4g/m for 2 h. To be applied as liquid or from discs.

(b) Methyl bromide

0C or above; 4g/m for 4 h.

4. RATS, RABBITS AND SNAKES IN GARBAGE AND RUBBISH DUMPS, BURROWS IN FIELDS AND OTHER HARBOURAGES

(a) Hydrogen cyanide (HCN) from calcium cyanide

Calcium cyanide dust is blown by special duster into one hole, and all others from which dust is seen to emerge are plugged. 1C or above.

(b) Phosphine

Add tablets containing aluminium or magnesium phosphide to the burrow, pack opening with crumpled newspaper and seal tightly by shovelling soil over the entrance.Treat re-opened burrows one or two days after the initial treatment. Special restrictions on the use of this material are made in some countries to protect endangered species of wildlife. All instructions given on the label should be carefully followed.

5. MOLES, WOODCHUCKS, GROUND SQUIRRELS OR PRAIRIE DOGS IN BURROWS, RUNWAYS OR COLONIES

(a) Hydrogen cyanide (HCN)

About 50 9 calcium cyanide per burrow at 1C or above.

(b) Methyl bromide

10 ml per burrow. A complete mole runway system should be treated in one operation by making openings every 75 to 150 mm (3 to 6 in) along the system and blowing calcium cyanide dust or injecting methyl bromide, closing each hole after application.

(c) Phosphine

See 4 (b) above.

6. ANTHILLS AND NESTS, TERMITE MOUNDS AND COLONIES, AND WASP AND HORNETS' NESTS

(a) Hydrogen cyanide (HCN) from calcium cyanide

Drop small amounts into nests from spoons or, in larger colonies, blow from dusters. 10C or above.

(b) Carbon disulphide

Pour into nests or colonies. 10C or above. Do not apply when ground is too dry because fumigant diffuses away rapidly.

7. SNAILS IN CARGO AND IN CARGO SPACES OF SHIPS

Foreign species of snails of medical or agricultural importance may be found in imported cargoes especially military material which may have been left standing outdoors before shipment. Residual populations may be found in the cargo spaces. These snails may be in a condition of aestivation and therefore very difficult to kill. The problem and methods of control by fumigation are fully discussed by Richardson and Roth (1963 and 1965). The identification and economic significance of snails likely to be accidentally imported into the United States are discussed by Burch (1960).

Treatments at atmospheric pressure may be conducted under gas-proof sheets or in shipping sheds, warehouses etc. as long as lethal concentrations are sustained. Under these conditions a continuous check must be kept by means of the thermal conductivity analyser or other suitable analytical method.

The following treatments are essentially summaries of those contained in USDA (1976). The species of snails listed are those usually found under the conditions described above.

Achatina fulica

(a) Methyl bromide at atmospheric pressure: 128g/m for 24 h at 12C and above.

65g/m minimum concentration at 2 - 12 h.
35g/m minimum concentration at 12 - 24 h.

(b) Hydrogen cyanide (HCN) at atmospheric pressure: 48g/m at 12C and above.

(c) Ethylene oxide/carbon dioxide 1:9 for 24 h at 12C and above.

145g/m minimum concentration at 2 - 4 h.
135g/m minimum concentration at 4 - 24 h.

Cochlicella and Hellicella spp.

Methyl bromide at atmospheric pressure: 128g/m for 72 h at 12C and above.
95g/m minimum concentration within 30 min.
40g/m minimum concentration within 48 to 72 h.

Theba pisana

(a) Methyl bromide at atmospheric pressure: 96g/m for 10 h at 27C and above and for 16 h at 13 to 26 C.

70g/m minimum concentration for first 30 min.
40g/m minimum concentration for 30 min to the end.

This schedule can also be used for Helix spp., Otala spp. and Succinea horticola.

(b) Hydrogen cyanide (HCN)

24g/m for 24 h at 18C and above.

Vacuum fumigation of miscellaneous cargo

Methyl bromide in 100 mm Hg pressure sustained vacuum.

(a) Cochlicella and Helicella spp: 128g/m for 16 h at 21C and above.

(b) Theba pisano: 96g/m for 6 h at 21C and above.


Appendices

Efficient utilization of fumigation sheeting

Bowen (1961) has published tables giving the dimensions of stacks of goods for maximum volume under gas-proof sheets of various shapes and sizes. As Bowen points out, efficient stacking may permit maximum utilization of available sheets and use of only one rather than two or more fumigations of a given load. He also emphasizes the following points.

1. The square is the best shape for the sheet if the highest ratio of stack volume to sheet is to be achieved. In joining sheets together, therefore, the combination should be as nearly square as possible.

2. The base of the ideal stack will resemble the shape of the sheet used to cover it.

3. Large sheets are more efficient because of the surface to volume relationship.

In the two tables, given here in abbreviated form, the dimensions in feet and metres are calculated from the formula derived by Bowen as follows:

The formula derived for computing the height h of stack for maximum volume under the sheet is,

(1)

in which L and W are the effective length and width of the sheet, i.e. the length and width after deducting the overlap at the bottom for sealing. The length 1 and the width w of the ideal stack are then determined by the following relationships:

l = L - 2h (2)

w = W - 2h (3)

If the length and width of the sheet are equal, it becomes a square with effective side A = L = W. Equation (1) for h then reduces to, h = A (4)

and the base of the stack of maximum volume that can be covered by the sheet will also be a square with side a such that,

a = A - 2h = (2A)/3 (5)

Dimensions of stack in metres for maximum volume under square sheets of various sizes allowing for 1-metre overlap (margin) at base of stack

Sheets1

Stack dimensions for maximum volume

Maximum volume

Actual
W x L
Effective
W x L
Height Width Length  

Metres

Cubic metres

8 x 8 6 x 6 1 4 4 16.0
10 x 10 8 x 8 1.33 5.33 5.33 37.92
12 x 12 10 x 10 1.67 6.67 6.67 74.06
14 x 14 12 x 12 2.0 8.0 8.0 128.0
15 x 15 13 x 13 2.17 8.67 8.67 162.74
16 x 16 14 x 14 2.33 9.33 9 33 203.25
18 x 18 16 x 16 2.67 10.67 10.67 303.39
20 x 20 18 x 18 3.0 12.0 12.0 432.0

Dimensions of stack in feet for maximum volume allowing for 3-foot margin

Sheets1

Stack dimensions for maximum volume

Maximum volume
Atual
W x L
Effective
W x L
Height Width Length  

Feet

Cubic feet

25 x 25 19 x 19 3.17 12.67 12.67 509
30 x 30 24 x 24 4.00 16.00 16.00 1 024
35 x 35 29 x 29 4.83 19.34 19.34 1 807
40 x 40 34 x 34 5.67 22.67 22.67 2 914
45 x 45 39 x 39 6.50 26.00 26.00 4 394
50 x 50 46 x 46 7.67 30.67 30.67 7 215

1W x L = Width by lenght

Thanks are extended to M.F. Bowen of Millbrae, California, for permission to reproduce his calculations in abbreviated form.


Contents - Previous - Next