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Is Your Grain Store Harvest Ready?

16 August 2022

Although grain prices are at unprecedented levels in relative terms this harvest, the high levels of volatility and harvest concerns elsewhere means that taking time to prepare grain stores properly could pay dividends by avoiding costly infestations and quality issues. Remember, grain found to contain any insects will be rejected and this leads to costly redirection, treatment and redelivery costs as well as a potential loss of any premiums. 

Grain store preparation and management follows the general principles of Integrated Pest Management (IPM) – that is Prevention through thorough cleaning, store preparation and storing at a suitable moisture and temperature, Monitoring the site for infestations or problems with bulk and their subsequent Control.  

Give the Store a Thorough Clean from Top to Bottom 

Insect infestations in grain stores are most likely to have originated from grain or dust carried over from the previous year therefore the key to grain store preparation is good hygiene and it is vital that that the whole store is cleaned thoroughly. This even includes the more awkward and hard to reach places and it’s important that this process begins soon after the shed is emptied. It is not just the floors and walls that need cleaning but any surface within the building from its fabric to fittings. This therefore includes the roof, purlins, machinery and underfloor ducts etc- all of these can act as havens for insect pests, most of which can survive right through to the following harvest even through the store has been emptied some time. This is where industrial hoovers or airlines from a compressor can play a key role in the cleaning process and just because a surface looks clean, there may still be insects present with even small quantities of grain or dust acting as a food source. In addition, these tools should also help remove any fungi present. When cleaning, always start at the top of the roof and work downwards as dust and debris should fall to the floor to be picked up with the hoover and always dispose of cleanings well away from the grain store. 

Stores should also be checked that they are still structurally sound – even checking that the roof is still watertight and stores should be rodent and bird proof. Cracks in walls and floors are not just a sign of damage but can also harbour insect pests. A good store should also be well ventilated so fans and vents should be tested with lights having shatter proof covers. Ideally the cleaning should begin as soon as the store is emptied however empty grain stores can also be tempting areas to tip feeds and store materials or machinery over the spring and summer – these also can act as places which can harbour grain pests and as such should be removed from the shed before pre-harvest cleaning.   

Once Clean – Monitor for Pests 

After the store has been made as clean as possible, it is important to monitor for the presence and type of pests. The use of secure bait boxes can be used to identify and control rodent activity although care should be given to prevent any potential contamination with grain or risk to non-target species. Insect pests can also be monitored with the use of traps (pitfall or pheromone sticky traps). These should be strategically placed through the store (according to manufacturer’s guidance) and monitored for activity on at least a weekly basis and the extent of any infestation can be gauged by increasing the number of traps.  

Good records are also useful, as they can highlight previous issues and allow store treatments to be tailored accordingly. 

What Are The Main Pests and What Damage Do They Do? 

Grain store insect pests fall into two categories – Primary pests which infest undamaged grains and Secondary pests, which feed on damaged grain and dust. 

One of the best-known insect pests is the Grain Weevil, recognised by its large snout relative to its body. As well as both the adults and larvae feeding on the grain, females lay their eggs within the grain and the damage is visible as holes in the grain, caused as their young emerge and bore their way out. 

The Saw Tooth Grain Beetle is another notable pest, which feeds on the embryo or germ of broken grains, ironically this also includes using the holes created by Grain Weevils. Saw Tooth Grain Beetles can also multiply very quickly with females capable of laying up to 400 eggs in a lifetime. As an infestation increases, this can lead to the grain heating, causing further damage and a deterioration in quality. 

Other insect pests include mites, which feed mainly on the grain germ, and taint produce by spreading fungal spores and allergens. Mite infestations can also develop very quickly if conditions allow due their ability to reproduce quickly. 

When preparing a grain store, it is not just insect pests that need to be considered. Rodents can cause considerable damage not only by gnawing and eating grains, but their urine and droppings can be significant contaminants. As mentioned earlier, birds should also be excluded from the store.  

What To Do if Insects Are Found

If insect pests are found there are several chemical options available despite the loss of some actives and formats in recent years. 

Before using a pesticide, it is important to consider the market for the grain, with some treatments unsuitable for grain going for human consumption and if in doubt speak to your buyer. 

Empty grain stores can be treated with pyrethroids, applied by a knapsack sprayer. Like the cleaning process, its important to treat the whole store, from floors and walls to machinery and fabric of the building itself so the sprayer needs to be able to reach some of those harder to reach places. The use of contractors may improve access by the use of high pressure sprays or mists. The use of Smoke products containing pirimiphos-methyl can also be used but only following the use of an insecticide spray first with the smoke offering further penetration of more awkward places e.g. up in the roof space. Ideally this should be done at least 6 weeks before harvest for optimum effectiveness. 

Further monitoring should then be undertaken to assess that the treatments have been successful. 

It is also important to note that cleaning and treating grain stores places operators at considerable risks from dusts, harmful chemicals and working at heights. As such, appropriate PPE should be worn and safety procedures put in place and before any treatment takes place, labels should be read and understood. 


Getting your store ready for harvest and the grain storage season comes down to good preparation. Taking the time to clean thoroughly, monitor for any pests and treating according is the first step towards good grain storage for the winter.   

heap of grain

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