Where is infestation happening in the supply chain?

17 February 20207 min reading

“The industry is full of HACCP certificates that offer nothing more than a hanging paper. The industry is full of fumigation certificates that do not certify successful treatments. Papers do not solve problems. Accurately designed processes and precision application will keep the brand safe. Modern technology offers solutions, we should use every weapon available!”

Vasilis Sotiroudas Pest Management Expert Centaur

Grain is moving from field to silos, warehouses and bunkers, on trucks, railcars, ships, barges and containers. This constant move and change of storage and transport assets creates two serious challenges. One is traceability. The other one that we face on this article is insect infestation.

Stored product insects can survive the harsh winters of the north and the hot temperatures of the tropics. They can survive the passing through elevators and screens, they can escape cleaning and they multiply so rapidly and massively that you can safely bet that always an insect will survive, no matter the control method.

We need to identify where insects infest grain and prevent this from happening or fight them early enough.

HARVESTING THE FIELDS Australian researchers found that in 9 out of 10 cases the harvesting machines carry a large number of insects before starting the year harvest. These insects feed on remains of the previous crop as a result of poor cleaning. These insects found in the combine harvesters and on the trucks that move grain from the field to farm, become the first source of infestation in the supply chain.

The solution is simple and obvious: Thorough cleaning of the harvesting equipment at the end of the season and spraying with a contact insecticide.

FARM STORAGE Bins, sheds and bunkers protect the grain in the first part of the supply chain. As in all grain storage areas, insect management needs 3 basic steps: Prevention, Monitoring and Control. Prevention comes by making the buildings pest proof. This means that insects cannot easily find their way in the asset as there are no openings, there are screens on windows and personnel is trained to keep doors closed. Another way to prevent insect development is cleaning. When food is not available insects will not stay. Monitoring for the presence of insects is done with the use of pheromone and UV traps and through regular inspections and grain sampling. The use of these traps in sheds and silos full of grain is not possible. The latest trend uses wireless sensors ( positioned in the bins and warehouses to measure temperature, moisture, hotspots and CO2. These parameters allow an algorithm to identify the presence of insects and predict the development of their population. The system of sensors may even assess the effectiveness of a fumigation. Control of insects is achieved using various methods like A) spraying and fogging on grain and on clean empty bins, B) using diatomaceous earth and C) using fumigants or controlled atmosphere.

Photo 1: Silo analytics

BULK CARRIERS The weak point in moving grain on ships and barges is fumigation. Very often grain is fumigated in transit for two reasons: a) as part of quarantine regulations and b) because voyage duration usually exceeds the needed fumigation time. The basic reason that fumigations fail on ships is that the gas is not able to reach an equilibrium across the grain mass. A usual fumigant used in ship fumigations is phosphine. Phosphine is able to penetrate grain at a pace of 5 meters per day. As the fumigant is introduced on the grain surface after loading, it would reach the bottom of a Panamax vessel hold (20m) in 4 days plus 4 days for the actual treatment duration, it shows an 8-day treatment would be sufficient. This is not happening because this duration is not available in all cases, especially on grain moving from the black sea countries to Mediterranean ports. The major reason of fumigation failure in ships is the lack of gas recirculation. Convection currents move air inside the grain mass. The air moves to an opposite direction in the morning and in the night, depending on temperature differentiation. Convection currents carry the fumigant gas with them creating unstable concentration conditions. In most cases the fumigant never reaches the bottom of the grain hold in levels high enough to kill insect eggs. The solution lies on precision fumigation which is possible by using gas recirculation pumps and tubes and by using wireless sensors to monitor gas levels every 4 hours in all grain levels, in all holds.

Photo 2: Monitoring and prediction analytics for stored grain by

PORT SILOS AND ELEVATORS All silos must be cleaned and sprayed when empty. An inspection will also verify the effectiveness of the procedure. When silos are full, inspecting for infestation is not easy. Sampling can be a way to go but nowadays wireless sensors provide the feedback on our cellphones in real time. As described above in the “farm storage” paragraph, monitoring is possible through cognitive algorithms that corellate the change of grain condition with insect and mold development.

Silo fumigation is a challenge similar to ship hold fumigation described above. Gas recirculation, silo sealing and gas monitoring are elements of key importance for fumigation success. Gas recirculation must be applied in bins of all sizes as it was proven that even on a 5 meter silo the gas will fluctuate when the temperature difference between night and day is significant and internal air currents are created.

Photo 3: Remotely controlled heat treatment by

THE FLOUR MILL OR ANY OTHER FOOD AND FEED FACTORY Stored product insects love flour mills as they can always find food there and there is a vast selection of tubes, machines and crevices to hide and multiply. Stored product insects may enter through open doors and windows as in most cases they can survive around a food factory but the main infestation sources for mills are two: the grain to be processed and product returned from the market. Grain must enter the mill free of infestation, by maintaining a thorough inspection and fumigation plan on the external grain silos. The returned product must always be fumigated effectively before being re-processed.

It is proved that in most cases, even when preventive measures are applied, the food factories get some level of infestation. The level shall be monitored by pheromone and UV traps. Although each factory has its own pest management plan a good target is to keep below 1,5 insects caught per trap per month. When this number is exceeded, a control method is needed. Mill fumigation with sulfuryl fluoride or even methyl bromide (in countries where still allowed) should be an option only when the mill can be made airtight. A method alternative to fumigation and still very successful is heat treatment of the entire mill and empty bins. This is a very fast method (24 hours) and gives excellent results when applied with precision.

Photo 4: Fumigation chambers by

BULK LOADING AND PACKING LINES It is very common to have insect eggs in the flour. This is happening when the flour is not going through entoleter machines (semolina), or when entoleters have not been properly maintained and do not offer a good kill of the eggs, or even when is all is properly used, a small number of eggs can still survive.

Packing lines are often accused for hiding insect populations. A thorough pest management system will identify the hot spots and packing lines would usually be among them. Areas with increased insect presence may be treated more often to keep populations down.

WAREHOUSES Final products are stored in various places from the plant warehouse to whole sellers, retailers and in the consumer’s pantry. All these stores can keep an insect population that is able to infest new coming products. Monitoring for insects is essential and a variety of control methods is available when a problem is found.

PROCESS AND PRECISION The industry is full of HACCP certificates that offer nothing more than a hanging paper. The industry is full of fumigation certificates that do not certify successful treatments. Papers do not solve problems. Accurately designed processes and precision application will keep the brand safe. Modern technology offers solutions, we should use every weapon available!

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