AU730991B2 - Fumigation composition and method - Google Patents

Description

Our Ref: 639290 P/00/011 Regulation 3:2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Applicant(s): Address for Service: Commonwealth Scientific and Industrial Research Organisation Limestone Avenue Campbell ACT 2601

AUSTRALIA

DAVIES COLLISON CAVE Patent Trade Mark Attorneys Level 10, 10 Barrack Street SYDNEY NSW 2000 Invention Title: Fumigation composition and method The following statement is a full description of this invention, including the best method of performing it known to me:- 5020 P:WPDOCS\MMB.SPEC.585298.6 May, 1996 1 FUMIGATION COMPOSITION AND METHOD FIELD OF THE INVENTION The present invention relates to a fumigant composition as well as a method of its use in the fumigation of commodities.

BACKGROUND OF THE INVENTION The present invention has been conceived with the express intention of finding a suitable fumigant for the disinfestation of cut flowers. However, it is to be noted that the invention is by no means limited to the disinfestation of cut flowers, but has broad applications for the fumigation of a large number of commodities from a broad range of S 15 biota. Up until the present time the disinfestation of cut flowers has been achieved predominantly with the use of methyl bromide. There are however, various problems associated with the use of methyl bromide. In particular, it has been found that methyl bromide is phytotoxic at concentrations necessary for quarantine fumigation of cut flowers (Stout, 1983 and Weller et al, 1995), and it is expected that due to toxicity and environmental concerns the Montreal Protocol will require use of methyl bromide to be phased out. Accordingly therefore, it is necessary to develop new fumigant compositions.

While the use of phosphine has been considered as a fumigant for various commodities, this also can be problematic in that a long exposure time, (in the order of 15 hours) is required, and the fumigation must be conducted at or above 15 0 C. As will be recognised, it is often desirable, especially for the fumigation of cut flowers, fruit or vegetables, that the fumigation be conducted at a substantially lower temperature in order that the commodity is not spoilt. Additionally, phosphine is known to be relatively ineffective against a number of insects and is reported to be ineffective in the control of mites (Bowley, C. R. and Bell, C. 1981 Journal of Stored Products Research, 29, 277-282).

It can be seen then that there is not presently available a fumigant composition which can P:\WPDOCS\MMB.SPEC.585298.6 May, 1996 -2be used in relation to a broad range of commodities and which is toxic against a broad range of biota.

It is therefore an object of the present invention to develop a novel fumigation composition which is effective against a broad range of biota for use on a broad range of commodities, and wherein the fumigation process can be conducted effectively, if so desired, at temperatures between 0°C and 30 0

C.

It is also an object of the present invention to provide a fumigant composition which will be effective for fumigating cut flowers and other perishable commodities.

Other objects of the present invention will become apparent from the following description thereof.

SUMMARY OF THE INVENTION According to one embodiment of the present invention there is provided a fumigant composition which comprises phosphine and carbonyl sulphide.

According to another embodiment of the present invention there is provided a fumigant composition which comprises phosphine, carbonyl sulphide and an inert carrier gas.

Preferably, the inert carrier gas is air, oxygen, carbon dioxide, nitrogen or a mixture of two or more of these gases.

According to a preferred embodiment of the invention, phosphine is present in a concentration of between about 0.04 mg/L and about 5 mg/L and carbonyl sulphide is present in a concentration of between about 1 mg/L and about 15 mg/L. Preferably, phosphine is present in a concentration of between about 0.5 mg/L and about 5 mg/L.

P:\WPDOCS\MMB. SPEC.585298.6 May, 1996 -3- According to another embodiment of the present invention there is provided a method of fumigation of a commodity which comprises treating the commodity with a fumigant composition comprising phosphine and carbonyl sulphide and optionally an inert carrier gas.

Preferably, in carrying out the method the phosphine is present in a concentration of between about 0.5 ing/L and about 5 mg/L and carbonyl sulphide is present in a concentration of between about 1 mg/L and about 15 mg/L. Preferably, the commodity being fumigated is cut flowers, vegetables, fruit, grain, pulses, nuts, seeds or wood.

According to another preferable embodiment of the method of the invention, the commodity being fumigated is stored in a sealed receptacle or enclosure during fumigation.

According to a still further embodiment of the invention, in the method of fumigation the inert carrier gas is air, oxygen, carbon dioxide, nitrogen or a mixture of two or more of these gases.

In another preferred form of the fumigation method, the commodity being fumigated is held at a temperature of between about 0°C to about 15 0 C, preferably between about 2°C to about 10 0 C for a period of between about one hour and about 15 days after exposure to the fumigant composition has ceased.

According to another embodiment of the invention the fumigant composition is applied to a commodity for a period of between about 1 and about 15 days at temperatures of below about 12 0 C, wherein an economic loss or reduction in commodity quality would result if the commodity were kept at higher temperatures.

According to a still further embodiment of the invention the fumigant composition is applied to a commodity in a reduced oxygen atmosphere to enhance toxicity of the P:\WPDOCS\MMB. SPEC.585298.6 May, 1996 fumigant composition. Preferably, the fumigant composition is applied in association with carbon dioxide.

DETAILED DESCRIPTION OF THE INVENTION As used throughout this specification, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising" will be understood to imply the inclusion of a stated element or integer or group of elements or integers but not the exclusion of any other element or integer or group of elements or integers.

As described above the fumigant composition according to the present invention is comprised of phosphine and carbonyl sulphide. Phosphine (PH 3 is correctly known as phosphorous (III) hydride and also goes by the name of phosphane and monophosphane.

Phosphine can be manufactured by the reaction of water or dilute acid with metal phosphides such as for example:- Ca 3

P

2 +6H 2 0 2PH 3 +3Ca(OH), Phosphine can also be manufactured by disproportionation of white phosphorous in alkalide hydroxide solutions, for example as follows:-

P

4 +3KOH+3H 2 0 PH 3 +3KH 2 P0 2 Phosphine is readily commercially available. Phosphine can be generated from aluminium phosphide, which is available commercially from various manufacturers such as Detia Degesch, Casa Bernado and United Phosphorus Ltd. It is also provided in a cylinder mixed with carbon dioxide by BOC Gases. Phosphine refers to phosphine sourced from any commercial source.

Carbonyl sulphide (COS) can be manufactured from the direct reaction of carbon P:\WPDOCS\MMB.SPEC.585298.6 May. 1996 monoxide and hydrogen sulphide. Carbonyl sulphide can be generated by the addition of potassium thiocyanate to sulphuric acid (Ferm (1957) The Chemistry of carbonyl sulphide. Chemical reviews 57, 621-640). Amines react readily with carbonyl sulphide at basic pH. In relation to the fumigation methods described herein, reaction of carbonyl sulphide with amines is to be avoided. Carbonyl sulphide is also readily commercially available. Carbonyl sulphide is available commercially from companies such as BOC Gases and Matheson Gas Products.

In a preferred form of the invention the phosphine/carbonyl sulphide composition is used 1o in association with an inert carrier gas. Examples of suitable inert carrier gases are air, oxygen, carbon dioxide and nitrogen. It is to be stressed however that the inert carrier gases mentioned herein have been mentioned by way of example only and that any suitable inert carrier gas can be utilised in association with the present invention. It is also possible for combinations of two or more inert carrier gases to be used.

Preferably, phosphine is present in a concentration of between about 0.04 mg/L and about 5 mg/L and carbonyl sulphide is present in a concentration of between about 1 mg/L and about 15 mg/L.

It is envisaged that the fumigant composition according to the present invention will be ,'useful in fumigation of perishables such as cut flowers, fruit and vegetables as well as grains, legumes, nuts, seeds and wood. The inventive composition is especially useful for fumigation of "cold durable" commodities. The present invention is especially useful in two applications. The first applies to perishable commodities such as cut flowers, fruit and vegetables as the effectiveness of fumigation at low temperatures minimises the harmful effects of raising the temperature of the produce to undertake fumigation. The second applies to durable commodities such as nuts, grains, pulses and oil seeds, where raising the temperature of the commodities to a level suitable for fumigation with currently available fumigants incurs a cost penalty. The fumigant composition according to the present invention is effective against a broad range of biota including bacteria, viruses, P:\WPDOCS\MMB.SPEC.585298.6 May, 1996 -6fungi, insects, nematodes, small reptiles and rodents. The present invention is particularly useful against the orders Colembola, Coleoptera, Diptera, Formicidae, Hymenoptera, Psocoptera, Neuroptera, Thysanoptera, Acari and terrestrial Crustaceans (such as slaters).

The composition of the invention is especially effective in treating perishables such as cut flowers, fruit and vegetables and other commodities which are cold tolerant, as the process of fumigation using the inventive composition can be carried out at temperatures as low as 0 0 C. It is also noted that relative to the use of phosphine in isolation, the inventive composition exhibits improved toxicity against ants (Formicidae), mites (Acari) and spiders (Arachnida), Diptera, Coleoptera and Colembola species. Similarly, the inventive composition exhibits improved toxicity relative to the use of carbonyl sulphide alone in relation to ants. The improved toxicity of the combination of phosphine and carbonyl sulphide relative to either phosphine or carbonyl sulphide in isolation at temperatures in the range of 5 0 C to 25 0 C is most unexpected. Similarly unexpected is the fact that S" 15 relative to the use of either of the isolated components of the inventive composition, the composition of the invention exhibits lethal toxicity to insect species at low temperature.

It has also been dhexpectedly revealed in experimental tests of the inventive composition that-.post-treatmeit mortality of insect species is enhanced when the post-treatment holding temperature is about 0°C to about 15 0 C or below, preferably about 2 0 C to about 10 0

C

compared to a post-treatment holding temperature of about 20 0 C. This again has important implications for fumigation of perishable and cold durable commodities. The post-treatment holding of commodities at low temperature may be conducted for between about 1 hour and about 15 days, depending upon individual circumstances such as the nature or the commodity and pest biota and the concentration of fumigant used. It is to be stressed however that post-treatment holding at low temperature is merely an optional feature of the process according to the invention.

The present invention also relates to a method of fumigation of a commodity wherein the commodity is treated with the fumigant composition according to the invention, optionally -7- P:\WPDOCS\MMB.SPEC.585298.6 May, 1996 in the presence of an inert carrier gas as referred to above. During this treatment it is naturally preferred that the commodity is stored in a sealed receptacle or enclosure such as for example, a barrel, shipping container, or large storage facility such as a silo. The fumigant composition can then easily be introduced into the receptacle or enclosure by mixture with an inert carrier gas which is then vented into the receptacle or enclosure.

The fumigant may be released into the chamber in a number of ways, including 1. release of each.gas from separate cylinders.

2. release of phosphine from pellets or tablets in water and introduction of carbonyl sulphide from a cylinder.

3. introduction of the gases simultaneously or sequentially.

4. release of the mixture, possibly in a carrier gas such as nitrogen, from a single cylinder.

.o 15 The present invention will now be further described with reference to the following examples. For the purpose of the examples, the following general protocol was followed: Each fumigation undertaken in the work, described here, used the same basic protocol for the production and measuring of the gases used.

Unless otherwise stated, the concentrated "source" gases, carbonyl sulphide (COS) and phosphine (PH 3 were generated in the laboratory. Carbonyl sulphide (COS) was either produced by the addition of potassium thiocyanate to sulphuric acid and the resultant gas passed through a lead acetate solution to remove any associated hydrogen sulphide (Ferm, 1957) or alternatively, sourced from compressed gas cylinders supplied by BOC Australia (purity Phosphine was generated by addition of aluminium phosphide tablets (Phostoxin, Degesch, Germany) to 5% aqueous sulphuric acid (Anon., 1975).

Prior to each experiment the concentration of each source gas was determined using a Gow Mac model 11-625 gas density detector on a Tracor MT150 gas chromatograph (GC) fitted P:\WPDOCS\MMB.SPEC.585298.6 May, 1996 -8with a Porapak Q 80/100 column.

Confirmation of fumigant concentrations, in each chamber, was made using gas chromatography techniques. Both carbonyl sulphide and phosphine were analysed using a Tracor MT-220 GC fitted with a Flame Photometer Detector (sulphur mode for carbonyl sulphide, and phosphorus mode for phosphine) and a Haye Sep Q 80/100 mesh column run at 110°C isothermal.

Fumigant concentrations were confirmed after the initial dosing and measured again just prior to the completion of the exposure.

Example 1 Effectiveness of a mixture of carbonyl sulphide and phosphine on Ants (Formicidae: 15 Hymenoptera).

Aim: To assess the effectiveness of a mixture of carbonyl sulphide and phosphine on ants.

Methods: Meat ants (Iridomyrexpurpureus) (Formicidae: Hymenoptera) were collected in a pit fall trap from a nest on site. They were immediately chilled and distributed, 20 ants per 270 mL flask or 100 ants in open, fluon rimmed jars inside 2.5 L desiccators. Fumigations were undertaken at a range of temperatures 10, and 15 0 C) by injecting concentrated source gases through rubber septa fittings into the sealed chambers.

At the completion of fumigation (5 hours for experiments 1; 24 hours for Experiment 2), the flasks were aired for 20 minutes and the ants placed into fresh containers with access to honey solution. Mortality was assessed at 24 hours after fumigation and again 3 days following fumigation.

P:\WPDOCS\MMB.SPEC.585298.6 May, 1996 -9 Results: Experiment 1.

hour fumigation (100 ants/test) Temperature

C

0

C)

5 10 15 15 15

PH

3 (mg/L) COS (mgIL) 24 hour Mortality 0 0 9 100 0 0 0 100 0 2 1 100 3 day Mortality 4 0 9 100 0 0 0 100 7 17 100 C C

C

C.

C Experiment 2.

24 hour fumigation (100 ants/test) Temperature

CDC)

5 5 10 15

PH

3 (mg/L) 0 1 0 1 0 1 0 1 0 1 0 1 COS (mg/L) 0 0 5 5 0 0 5 5 0 0 5 5 24 hour Mortality 0 0 100 100 1 0 100 100 0 6 1 100 3 day Mortality 1 27 100 100 16 100 100 77 66 100 100 P:\WPDOCS\MMB.SPEC.585298.6 May, 1996 Discussion: The use of a mixture of carbonyl sulphide and phosphine resulted in higher mortality than fumigating with either of these fumigants alone. The mixture of carbonyl sulphide and phosphine, results in a better kill given a short exposure time (5 hours) than either COS or PH 3 Although use of COS over 24 hours is effective against meat ants (Iridomyrex purpureus) at 5 and 10*C it is not always practical to fumigate or to maintain fumigation concentrations for that length of time. The mixture was effective at low temperatures 0

C).

Example 2 Assessment of the efficacy of a mixture of carbonyl sulphide and phosphine at a range of temperatures against the rice weevil (Sitophilus oryzae) (Coleoptera: Curculionidae).

Aim: To assess the effect of a mixture of carbonyl sulphide and phosphine on Sitophilus oryzae.

Methods: Cultures of S. oryzae were acclimatised to 10, 15 and 25 0 C. Acclimatisation was achieved by moving cultures step wise (at 5 0 C per step) at 5 day intervals from the rearing temperature of 25 0 C to the test temperatures of 10,15 and 25 0 C. Once at the temperature for testing they were held at that temperature for a further 14 days before testing.

All tests were carried out in desiccators (approx. vol. 2.7 The S. oryzae (and culture medium) were placed in small crystallising dishes (with a fluon rim) on racks within the desiccators. At each temperature 4 desiccators were set up, one with no fumigants added, one with 1 mg/L PH 3 one with 5 mg/L COS and the fourth with 1 mg/L PH 3 and 5 mg/L

COS.

P:\WPDOCS\MMB.SPEC.585298.6 May, 1996 11 Desiccators were held at the test temperature for 24 hours prior of the test being undertaken. The desiccators were loaded with the insects and sealed at the test temperature, however, due to safety reasons, they were dosed and stirred in the fume hood (laboratory temperature 22 0 C) total time 5 minutes.

Following the fumigation (5 hours), all desiccators/cultures were aired off for 30 minutes at room temperature. After 30 minutes the cultures were returned to the test temperature.

The desiccators were held a further 24 hours after the completion of fumigation before the first mortality assessments were undertaken. Cultures were held at the test temperatures apart from the time taken to assess mortality. Mortality was assessed at 24 hours and 7 days.

Results: 0* 0*0.

0 Experiment 1.

5 hour Exposure 100 insects) Concentration Concentration

PH

3 mg/L COS mg/L 1 0 1 0 1 0 0 5 0 5 0 5 1 5 1 5 1 5 0 0 0 0 Temperature

(C)

10 15 20 10 15 20 10 15 20 10 15 Mortality 24 hour 5.1 0 10.3 0 0 2.7 5.2 4.9 39.4 4.2 0.6 Mortality 7 Days 50.0 46.5 99.0 1.7 0.9 2.8 92.5 68.2 98.2 9.3 P:\WPDOCSMMB-.SPEC.585298.6 May, 1996 12 Experiment 2 hour Exposure 150 insects) Concentration PH, mg/L 1 1 1 0 105 0 0 0 20 0 Concentration COS mg/L 0 0 0 0 5 5 5 5 5 5 5 0 0 0 0 Temperature

C

0

C)

10 15 20 25 10 15 20 25 10 15 20 25 10 15 20 25 Mortality 24 hour 0 7 23 26 0 1 0 0 13 17 44 29 0 1 0 0 Mortality 7 Days 94 78 98 93 1 2 2 0 97 92 100 99 1 1 3 2 9* Experiment 3 hour Exposure 150 insects) Concentration 25 PH 3 mg/L 0 0 0 0 1 0 0 0 Concentration COS mgIL 0 0 0 0 5 5 5 5 5 0 0 0 0 Temperature

CC)

10 15 20 25 10 15 20 25 10 15 20 25 10 15 20 25 Mortality 24 hour 0 .6.5 19.4 26.0 0 1.0 0 0 15 18.2 35.7 28.8 1.4 1.1 0.5 0 Mortality 7 Days 93.9 77.8 97.8 93.4 0.2 0 97.1 92.5 100.0 98.4 2.7 0.6 2.6 0.2 P:\WPDOCS\MMB.SPEC.585298.6 May, 1996 13- Discussion: The mixture of carbonyl sulphide and phosphine was not antagonistic at any tested temperature. It was more effective than carbonyl sulphide alone in all experiments and slightly more effective than phosphine alone in eleven out of twelve experiments.

Example 3 Assessment of the efficacy of a mixture of carbonyl sulphide and phosphine at a range of temperatures against the two-spotted mite (Tetranychus urticae) (Acaridae: Tetranychidae).

*ooo Aim: To assess the effectiveness of mixture of carbonyl sulphide and phosphine against two- 15 spotted mites (Tetranychus urticae).

Methods: Punnets of lupins seedlings, purchased from a local nursery, were infested with two spotted mites. The mites were maintained on the seedlings for ten days to ensure an even infestation of mixed ages. For fumigation, punnets of infested seedlings were subdivided and placed in desiccators (approx. vol. 2.7 At each temperature, 5, 10 15 and 20 0

C,

the desiccators were fumigated with 1 mg/L PH 3 5 mg/L COS and the combination of 1 mg/L PH 3 and 5 mg/L COS referred to in the results as a mixture of carbonyl sulphide and phosphine. One desiccator at each temperature remained unfumigated as a measure of mortality resulting from handling and being held at that temperature.

Desiccators were held at the test temperature for 24 hours prior of the test being undertaken. The desiccators were loaded with the infested plants and sealed at the test temperature, however, due to safety reasons, they were dosed and stirred in the fume hood (laboratory temperature 22 0 C) total time 5 minutes.

P:\WPDOCS\MMB.SPEC.585298.6 May, 1996 -14- Following the fumigation (5 hours), all desiccators/cultures were aired off for 30 minutes at room temperature. After 30 minutes the cultures were returned to the test temperature.

The desiccators were held a further 24 hours after the completion of fumigation before the first mortality numbers were counted. Mortality was assessed by removing a number of leaves from the lupins and assessing alive and dead present (with the total number counted being in the range of 100 200 adults). New leaves were sampled at each assessment.

Cultures were held at the test temperatures apart from the time taken to assess mortality.

Mortality was assessed at 24 hours and 7 days.

Results: The results of three replicates of the same experiment have been pooled and are presented below.

5 hour exposure 500 adults/entry m.ess otherwise indicated) 9S 5 9*S@

OS

Concentration PH, mg/L 1 20 1 1 25 1 1 1 1 *1 total no. of" *2 Concentration COS mg/L 5 5 5 5 5 5 5 Temperature 5 10 15 5 10 15 20 5 10 15 20 Mortality 24 hour 84.2 41.3 60.0 98.9 87.0 82.2 94.2 93.5 100 100 100 100 12.6 8.0 4.0 4.2 Mortality 7 Days 80.9 39.1 68.9 93.7 83.8 79.9 83.0 100*1 100 100 99.1*2 100 11.6 6.7 4.8 mites sampled 77 only newly emerged mites alive P:\WPDOCS\MMB.SPEC.585298.6 May, 1996 15 Discussion: For rapid disinfestation of two spotted mites (Tetranychus urticae), a mixture of carbonyl sulphide and phosphine on the basis of the results above is better than either PH 3 or COS used alone as fumigants. Across the temperature range tested, a five hour fumigation with a mixture of carbonyl sulphide and phosphine killed all mites present but did not kill 100 of mite eggs (see results, where a mixture of carbonyl sulphide and phosphine was applied at 15 0

C).

Example 4 Assessment of the efficacy of a mixture of carbonyl sulphide and phosphine against West Indian drywood termites (Cryptotermes brevis) (Isoptera: Kalotermitidae).

Aim: 15 To assess the effectiveness of a mixture of carbonyl sulphide and phosphine against West Indian drywood termites (Cryptotermes brevis) relative to fumigation with PH 3 or COS applied alone.

Methods: 20 Termites were fumigated in sealed desiccators (approximate volume 2.5 Termites 30) were placed in traps made of stainless steel mesh and placed in the desiccators.

Concentrated (source) gas was added to achieve the required fumigation concentration, and the air within the chamber was mixed using a magnetic stirrer. All fumigations were for hours at room temperature (approximately 22 0

C).

At the completion of fumigation, the flasks were aired for 20 minutes and the termites placed into fresh containers with access to honey solution. Mortality was assessed at 24 hours after fumigation and again 4 days following fumigation.

P:\WPDOCS\MMB.SPEC.585298.6 May, 1996 -16- Results: Experiment 1.

Concentration PH 3 Concentration COS mg/L mg/L 0 0 2 0 2 5 2 10 2 15 0 15 Experiment 2.

Concentration PH 3 Concentration COS mg/L mg/L 15 0 0 0 1 0 5 1 0 1 1 1 5 Mortality 4 hour 0 30 90 100 95 0 Mortality 24 hour 0 10 5 20 70 70 Mortality 24 hours 89 100 Mortality 48 hours 100 100 Discussion: The results presented above indicate that the combination of PH 3 and COS is faster acting and more effective on West Indian drywood termites (Cryptotermes brevis) than fumigation with either PH 3 or COS alone, over a 5 hour period.

Example Effect of a mixture of carbonyl sulphide and phosphine on Queensland fruit fly (Dacus tryoni) (Diptera: Tephritidae).

Aim: To determine whether a mixture of carbonyl sulphide and phosphine resulted in higher mortality than either PH 3 or COS fumigation of Queensland fruit fly (Dacus tryoni).

P:\WPDOCS\MMB.SPEC.585298.6 May, 1996 17- Methods: Eggs, larvae and adults of the Queensland fruit fly were fumigated at 25 0 C under humidified conditions in 2.5 L desiccators. Eggs (100 per test) and larvae (approx. 50 per test) were placed in open petri dishes on moistened green filter paper. Adults (approx 30 per test) were encapsulated in stainless steel mesh cages. Concentrated source gases were injected into the desiccators via a septum seal and the gasses mixed using a magnetic stirrer.

At the completion of fumigation, the flasks were aired for 20 minutes and the eggs and larvae kept moist on green filter paper for assessment the following day. Adults were returned to larger cages and given access to a honey solution. Mortality was assessed as egg hatch, larval mortality and adult death at 24 hours after fumigation.

Results: Concentration Concentration Egg Hatch Larval Adult

PH

3 mg/L COS mg/L mortality mortality 0 0 80 12 0 0 5 82 7 1 5 9 57 100 20 1 0 6 53 100 Discussion: Queensland fruit fly (Dacus tryoni) is an important pest of fruit, and subject of quarantine restriction in parts of Australia. These results indicate that PH 3 and a mixture of carbonyl sulphide and phosphine are effective against this pest. They also and demonstrate that there is no direct antagonism between the action of the mixture of these two fumigants with respect to the Queensland fruit fly.

Example 6 Effect of a mixture of carbonyl sulphide and phosphine on rose-grain aphids (Metopolophium dirhodum) (Hemiptera: Aphididae).

P:\WPDOCS\MMB.SPEC.585298.6 May, 1996 18- Aim: To test the effectiveness of a mixture of carbonyl sulphide and phosphine relative to either

PH

3 or COS on rose-grain aphids (Metopolophium dirhodum).

Methods: Fumigations of rose-grain aphid cultures on wheat tillers were undertaken at 5, 10 and 15 0

C

by injecting concentrated source gas into sealed desiccators fitted with a rubber septum. The gases were mixed using a magnetic stirrer for 3-4 minutes. All fumigations were of 5 hour duration.

At the completion of fumigation, the desiccators were aired for 20 minutes and the rosegrain aphid cultures transferred to holding chambers. Mortality was assessed 24 hours after fumigation by counting living and dead aphids on individual wheat tillers (to a total of 100 adults).

Results: Experiment 1.

Concentration PH 3 Concentration COS Temp.

mg/L mg/L °C 0 0 5 1 0 5 0 5 5 1 5 5 0 0 10 1 0 10 0 5 10 1 5 10 0 0 15 1 0 15 0 5 15 1 5 15 Mortality 24 hours 62 91 100 100 2 59 94 100 13 98 63 100 P:\WPDOCS\MMB.SPEC.585298.6 May, 1996 -19- Experiment 2.

Concentration PH 3 Concentration COS mg/L mg/L 0 0 1 0 0 5 1 5 0 0 S 1 0 0 5 1 5 0 0 1 0 S 0 5 1 5 Temp.

oC 5 5 5 5 10 10 10 10 15 15 15 15 Mortality 24 hours 87 91 100 7 100 3 100 100 Discussion: 20 Fumigation of free living stages of rose-grain aphids with a mixture of carbonyl sulphide and phosphine is more successful than either PH 3 or COS applied alone.

Example 7 Effect of a mixture of carbonyl sulphide and phosphine on Western Flower Thrip (Frankliniella occidentalis) (Thysanoptera: Thripidae).

Aim: To test the effectiveness of a mixture of carbonyl sulphide and phosphine against Wester Flower Thrip (WFT) compared with that of PH 3 and COS.

Methods: Approximately 15 adult WFT were placed in petri dishes and covered with perforated film.

These were in turn placed in the fumigation chamber (2.5 L desiccator) in lots of four such that each test contained a total of sixty adults. In addition to this, two large petri dishes of P:\WPDOCS\MMB.SPEC.585298.6 May, 1996 moist cottonwool containing leaf discs cut from freshly egged and whole leaves from mixed age cultures were placed in the fumigation chamber.

Fumigation was undertaken at room temperature (approximately 22 0 C) over a period of five hours. At the completion of fumigation the chambers were aired for 20 minutes, after which time the cultures were returned to a controlled temperature room (20-25 0

C).

Adult mortality and that of free living stages (mostly nymphs) on leaves were made after 24 hours. The leaf cultures were then held for a further six days to assess whether or not nymphs had emerged from fumigated eggs and were developing.

9 Results: Concentration Concentration Adult Nymph No. nymphs

PH

3 mg/L COS mg/L Mortality mortality emerging 0 0 4 15 26 0 15 100 100 0 S1 0 100 100 11 1 5 100 100 0 Discussion: These data show that adults and nymphs of WFT are readily killed by any of the three fumigation regimes tested. The addition of COS to PH 3 as a mixture of carbonyl sulphide and phosphine extends the kill achieved by PH 3 on WFT to include the egg stage thus providing improved disinfestation.

P:\WPDOCS\MMB.SPEC.585298.6 May, 1996 -21- Example 8 Effect of a mixture of carbonyl sulphide and phosphine on whitefly (Bemisia tabaci) (Hemiptera: Aleyrodidae) Aim: To test the effectiveness of a mixture of carbonyl sulphide and phosphine relative to either

PH

3 or COS on whitefly.

Methods: 10 Commercially purchased poinsettias were infested with adult whitefly and allowed to establish over 4-5 weeks, resulting in fairly evenly infested plants, each bearing the full range of life stages. Fumigations were undertaken by transferring individual pot plants to desiccators and injecting concentrated source gas through rubber septa fittings. All fumigations were done at 20 0 C and were 5 hours in duration.

At the completion of fumigation, the desiccators were aired for 20 minutes and the poinsettia transferred to holding chambers with screened bases to allow watering of the plants and funnel traps on top to collect emerging adults.

The number of adults caught in the funnel traps was recorded at intervals over 14 days post fumigation. After 14 days leaf sample were taken from each test plant and scored for the presence of live nymphs.

Results: Experiment 1.

Concentration Concentration No. Adults No. Adults after No. Adults after No. Adults after

PH

3 mg/L COS mg/L after 1 day 4 days 7 days 14 days 0 0 45 11 13 0 5 1 0 3 0 1 0 0 0 0 0 1 5 0 0 0 0 P:\WPDOCS\MMB. SPEC.585298.6 May, 1996 -22- All test plants were found to have live nymphs. Both the control and COS tests had well developed nymphs whereas PH3 and a mixture of carbonyl sulphide and phosphine had mainly first instars and an occasional second instar. Given the temperature regime maintained, the presence of well developed nymphs was expected (akin to those found in the control and COS test), therefore it would appear that PH 3 is retarding the development of egg/first instars.

Experiment 2.

Concentration Concentration No. Adults No. Adults after No. Adults after No. Adults after

PH

3 mg/L COS mg/L after 1 day 4 days 7 days 14 days 0 0 54 31 60 82 0 5 0 4 0 2 1 0 0 0 0 0 1 5 0 0 0 0 The score for nymphs observed after two weeks was in keeping with the results recorded for Experiment 1.

Discussion: Both PH 3 at 1 mg/L and COS at 5 mg/L achieved good adult mortality of whitefly, and no antagonism was observed with the mixture of carbonyl sulphide and phosphine.

Example 9 Assessment of Phytotoxicity Aim: To assess the phytotoxicity effects of a mixture of carbonyl sulphide and phosphine relative to methyl bromide (MeBr) (the fumigant currently used to disinfest cut flowers and ornamentals).

Methods: Carnations (white field) and margarite daisies purchased from a local wholesaler, were P:\WPDOCS\MMB.SPEC.585298.6 May, 1996 -23bunched placed in buckets containing 2 litres of fresh tap water and sealed in 63.5 litre drums fitted with a septa fitting. Flowers were fumigated with methyl bromide at 32 mg L"' for 2 hours (the recommended quarantine dose, (Stout, 1983) phosphine at 1 mg/L'' for hours, carbonyl sulphide at 5 mg/L-' for five hours and finally a mixture of 1 mgAL phosphine and 5 mg/L-' carbonyl sulphide for five hours at 22"C.

At the completion of the fumigations the flowers were aired in a fume cupboard for minutes, provided with fresh water and left at room temperature for four days before being assessed for damage/ premature ageing. All the bunches, including controls, were assessed by a panel of ten people in a blind test. Assessments of damage were scored out of 10 where 1 was as fresh as a daisy, 2-3 acceptable for sale, 3-5 some damage, 5-8 significant damage and 8-10 "only suitable for compost".

Results: Assessments of fumigated flowers, four days post fumigation.

15 Control MeBr PH, COS PH, COS Daisy Cam. Daisy Cam. Daisy Cam. Daisy Cam. Daisy Cam.

5 4 10 5 4 6 8 2 6 6 5 8 6 3 7 7 3 4 4 5 6 10 8 4 7 6 4 6 6 9 9 10 6 6 7 9 6 9 7 9 7 10 6 7 8 9 6 9 7 6 3 8 2 5 3 6 2 6 2 8 8 10 9 7 8 9 7 9 8 7 3 10 2 5 6 8 3 6 3 8 6 10 5 7 5 8 4 8 9 8 10 9 8 9 9 7 9 8 A "damage index" (Leesch, 1984) was calculated by dividing the sum of the ratings for the treated flowers by the sum of the ratings for the untreated flowers; ie Damage Index E treated ratings E untreated ratings A damage index of 1.0 infers that the fumigation had no deleterious effect, greater than infers damage, less than 1.0 infers improved performance.

-24- MeBr PH 3 COS PH 3

COS

Daisies 1.33 0.78 1.10 1.00 Carnations 0.98 1.12 0.75 0.93 Discussion: No significant damage resulted from the fumigation of carnations and daisies with a mixture of phosphine and carbonyl sulphide. It is also worth noting that the fumigation of these flowers with the mixture phytotoxicity of this mixture resulted in less than that of methyl bromide at the recommended quarantine dose.

*9*g 15 It is to be recognised that the present invention has been described by way of example only and that modifications and/or alterations which would be obvious to a person skilled in the art on the basis of the teaching herein are considered to be included within the scope and •g spirit of the invention as described.

9 The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that that prior art forms part of the common general knowledge in Australia.

*9999.

9 -9* P:\WPDOCS\MMB.SPEC.585298.6 May, 1996

REFERENCES

Anonymous (1975) Recommended methods for the detection and measurement of resistance of agricultural pests to pesticides. Tentative method for adults of some major pests of stored cereals, with methyl bromide and phosphine. FAO Method No 16. FAO Plant Prot. Bull., 23(1), 12-25.

Ferm R.J. (1957) The chemistry of carbonyl sulphide. Chemical Reviews, 57, 621-640.

Leesch, J.G. (1984) Fumigation of Lettuce: Efficacy and phytotoxicity. Journal of Economic Entomology, 77, 142-150 .o 15 Stout, 0.0. 1983. International Plant Quarantine treatment Manual. FAO Plant Production and Protection Paper No 50, FAO, Rome, Italy, x 220p.

99 Weller, van S. Graver, J.E. and Damcevski, 1995, Replacements for methyl bromide in quarantine treatments of cut flowers and ornamentals, Proc.

20 Australasian Postharvest Horticulture Conference, Melbourne, 18-22 September, 1995.

Claims (13)

1. A fumigant composition which comprises phosphine and carbonyl sulphide.

2. The fumigant composition as claimed in claim 1 further comprising an inert carrier gas.

3. The fumigant composition as claimed in claim 2 wherein the inert carrier gas is air, oxygen, carbon dioxide, nitrogen or a mixture of two or more of these gases.

4. The fumigant composition as claimed in either claim 2 or claim 3 wherein phosphine is present in a concentration of between about 0.04 mg/L and about mg/L and carbonyl sulphide is present in a concentration of between about 1 mg/L S" and about 15 mg/L

5. The fumigant composition as claimed in claim 4 wherein phosphine is present in a concentration of between about 0.5 mg/L and about 5 mg/L. o* o.

6. A method of fumigation of a commodity which comprises treating the commodity 20 with a fumigant composition comprising phosphine and carbonyl sulphide and optionally an inert carrier gas.

7. The method as claimed in claim 6 wherein the commodity being fumigated is stored in a sealed receptacle or enclosure during fumigation.

8. The method as claimed in either claim 6 or claim 7 wherein said inert carrier gas is air, oxygen, carbon dioxide, nitrogen or a mixture of two or more of these gases. P:\WPDOCS\MMB.SPEC585298.6 May, 1996 27

9. The method as claimed in either claim 7 or claim 8 wherein the phosphine is present in a concentration of between about 0.5 mg/L and about 5 mg/L and the carbonyl sulphide is present in a concentration of between about 1 mg/L and about mg/L. The method of any one of claims 6 to 9 wherein the commodity being fumigated is cut flowers, vegetables, fruit, grain, pulses, nuts, seeds or wood.

11. The method as claimed in any one of claims 6 to 10 wherein the commodity being fumigated is held at a temperature of between about 0°C to about 15°C for a period of between about one hour and about 15 days after exposure to the fumigant composition has ceased.

12. The method as claimed in claim 11 wherein the commodity being fumigated is held at a temperature of between about 2 0 C to about 10 0 C for a period of between about one hour and about 15 days after exposure to the fumigant composition has ceased.

13. The method as claimed in any one of claims 7 to 12 wherein the fumigant 20 composition is applied to a commodity in a reduced oxygen atmosphere to enhance toxicity of the fumigant composition.

14. The method as claimed in claim 13 wherein the fumigant composition is applied in association with carbon dioxide. P:\WPDOCS\MMB.SPEC.585298.6 May, 1996 28 The method as claimed in any one of claims 6 to 14 wherein the fumigant composition is applied to a commodity for a period of between about 1 and about days at temperatures of below about 12 0 C, in circumstances where an economic loss or reduction in commodity quality would result if the commodity were kept at higher temperatures. Dated this 6th day of May, 1997. I J S 15 COMMONWEALTH SCIENTIFIC AND INDUSTRIAL ORGANISATION By Its Patent Attorneys DAVIES COLLISON CAVE 0050