Achieving Effective Fumigation

Achieving Effective Fumigation

With the 2023 harvested grain safely stored in silos, it is time to put an economic value on your grain and think about how you will go about protecting this value when it comes time to market your asset.

With the advantages of on-farm storage being realised by many farmers across the country, ensuring the value of your grain is protected is a priority. Australia has the strictest standards for insect infestation, with zero tolerance for live insects in stored grain.

Meeting these strict guidelines is vital to avoiding load downgrades and rejections and ensuring the best value for your grain is achieved. Having a load rejected or downgraded can be a costly exercise when additional freight and fumigation are factored in.

Australian ports are held to this same standard and finding one live insect in grain waiting to be exported can have costly ramifications. Grain that needs to be quarantined will delay a ship’s departure and, in some cases, may result in a vessel being sent to another port to finish loading, which is a costly outcome.

Controlling insect infestation is an area of expertise for Kotzur Pty Ltd, which for over 70 years has been leading the way in grain storage and handling efficiency, technology and knowledge. Managing Director Andrew Kotzur has a long history in the industry, and through research with the Stored Grains Research Laboratory (a division of CSIRO), Kotzur was able to validate the required levels of silo sealing, fumigation dispensing and recirculation to achieve full fumigation in stored grain.

Previous trials (eg – William, Nickson, Braby & Henderson, CSIRO Division of Entomology 1989 Goorambat Trial) concluded that fumigant does not naturally distribute well in larger silos (bins), thus requiring longer fumigation times, very good sealing and will result in higher absorption of gas into the grain.

However, the 2008 trials conducted by Kotzur and CSIRO proved that with suitable recirculation, the fumigant gas can be fully distributed at or above minimum concentrations within about 18 hours from starting fumigation.

A Kotzur GP18-10 (which holds approximately 1500T of wheat) was used for the trials and while the trials were based on using Phosphine, the principles apply for any gaseous fumigant.

Kotzur said the combination of a correctly sealed silo (minimum 5-minute pressure half-life), a good fumigant application (following the product recommendation), together with a recirculation system resulted in the minimum required concentrations of 360ppm phosphine throughout the entire silo volume within 36 hours. This compares with many days (or even weeks) in silos without recirculation.  

“Further trials with controlled leakage (i.e. a compromised silo seal) showed a high probability of failed fumigation, even with a relatively small leakage. Regular pressure tests and achieving a complete seal are essential to effective fumigation,” Andrew Kotzur said.

“It is also essential to reach the threshold concentration for a set period of time and maintain it there to ensure all the insects die.

“Sealed silos are paramount to maintaining the threshold concentration and any compromises to the seal can lose fumigant, let in new air and dilute the fumigant,” Mr Kotzur said..

To achieve effective fumigations, the silo must be sealable – gas-tight to the AS2628 standard to ensure all insects are killed. If all insects are not killed, they can develop resistance to the fumigant and pass it on to the next generation.

Equipment hygiene is another key task that Mr Kotzur reinforces when speaking with grain growers. Ensuring all equipment is thoroughly cleaned before harvest and storing a new crop is an essential step in preventing insect resilience to fumigants.

According to Plant Health Australia, one tonne of infested grain can produce more than one million insects during a year, which can walk and fly to other grain storages to start new infestations.1

Ben Kotzur is the third generation Kotzur to devote a career to silo design and manufacture and as the Chief Technical Officer, is passionate about the role silo design plays in achieving effective fumigation.

Phosphine is the most commonly used fumigant in Australia, so Kotzur fumigation boxes have been specifically designed for using the Phosphine tablets; fumigation boxes then distribute the gas evenly throughout the silo.

Designed following research conducted with the CSIRO, the fumigation box allows farmers to easily insert phosphine tablets into the box, which then interact with the moisture in the air inside the silo.

Ben Kotzur emphasised during fumigation it is important that air is turned over in a closed-circuit system to ensure the gas is evenly distributed throughout the entire silo to reach the kill target (insects).

Finally, Kotzur recommends these tips for ensuring clean and pest free grain:

  • – Remember the value of your grain in silo and make sure you protect that value
  • – Check / monitor your stored grain for infestation at regular intervals – use insect traps
  • – Thoroughly clean out your silo and harvest equipment for good hygiene and ensure there is no residual grain
  • – Ensure you carry out an effective fumigation

Kotzur takes pride in working with customers to design a system that works with the client’s needs for successful grain storage.