ProFume® and VaporMate® are available alternatives to phosphine, however they can only be applied by a licensed fumigator. Carbon dioxide and nitrogen are ‘controlled atmosphere’ alternatives to phosphine which can be done by anyone providing they have access to the required equipment and knowledge. All of these alternatives require a gas-tight storage for successful control of insects and are currently more expensive than phosphine. For more information see the back pages of ‘Fumigating with phosphine, other fumigants and controlled atmospheres’
If phosphine is not working what do I do?
1) The first thing to check is that the silo is gas-tight, ie that it meets at least a three minute, half-life pressure test. (Check before filling and when full as the weight of the grain can open gaps around the bottom slide plate.)
2) Check the application rate is enough to treat the entire storage volume.
3) Check the exposure period is long enough according to the grain temperature.
4) Get an expert to ensure you’ve correctly identified the insect pest, particularly if you suspect it’s the flat grain beetle, cryptolestes spp.
For more information see ‘Fumigating with phosphine, other fumigants and controlled atmospheres’
What type of rubber and sealant is best for sealing silos?
Polyurethane based rubbers and sealants should be used for sealing silos. Silicon based products can potentially contaminate the grain. Look for a rubber with a strong memory, that is one that springs back to its original shape after being compressed.
What’s the difference between a thermosiphon and active recirculation?
The theory of a thermosiphon is that it uses ambient temperature differentials to slowly move air in a pipe between the head space and the bottom of the silo. Active recirculation uses a fan in a sealed system to circulate the air from the bottom to the headspace of the silo. The application chamber where phosphine is applied must be large and open to the grain so it can disperse if the recirculation systems stops, otherwise explosive gas concentrations can be reached. For more information see ‘Fumigating with phosphine, other fumigants and controlled atmospheres’
What are phosphine ground application devices?
Rather than putting phosphine in the headspace, some silos are equipped with a ground application system. Phosphine is applied into a chamber at ground level and disperses’ through the grain via an opening into the bottom of the silo and/or via a sealed recirculation system. The important thing is that the phosphine has a large space in the application chamber and/or room to disperse freely into the grain so the gas concentration doesn’t reach explosive levels in the confined space. For more on phosphine application see ‘Grain fumigation – a guide’ or ‘Fumigating with phosphine, other fumigants and controlled atmospheres’
Do I need recirculation?
In silos over 150 tonne a sealed recirculation system is ideal to disperse the gas in a shorter time frame. The key is that the silo is gas-tight – that is, meets a five minute, half-life pressure test and the recirculation system won’t compromise that seal in the future. For more information see ‘Fumigating with phosphine, other fumigants and controlled atmospheres’
What does the Australian Standard 2628 mean?
The AS2628 was developed to form a common definition of a gas-tight, sealable silo which is suitable for fumigation. For a silo to meet the AS2628 it must perform a five minute, half-life pressure test. If a silo meets this pressure test, it will hold phosphine gas and other fumigants at a concentration high enough and for long enough to kill insects at all life stages (eggs, larvae, pupae). For more information see ‘Pressure testing sealable silos’
How can I choose a quality silo to buy?
The first thing to ask yourself is do I want the option to fumigate in the silo? If the answer is yes then you will need a gas-tight, sealable silo that meets the Australian Standard 2628. Ensure the manufacture or importer can guarantee this by performing a five minute, half-life pressure test once the silo is delivered or constructed. Getting it stated on the invoice is also a good idea as this forms part of your guarantee. For more tips on buying silos see ‘Silo buyer’s guide’
Where do insects live and can I clean up to keep them away from my storage?
Where do insects live and can I clean up to keep them away from my storage? A Insects typically like warm dark area’s with a source of food. Common places to find insects are in leftover bags of grain, under hoppers, in machinery where grain gets caught and under rubbish around storages. Cleaning grain storages, surrounding areas and grain handling machinery is the first line of defence against insects. For more on grain hygiene see ‘Hygiene and structural treatments for grain storages’
Performance testing aeration systems, GRDC CRCNPB, Fact sheet
