Pro Operator

Safe spraying in store

spraying grain stores

Time and effort spent cleaning, preparing and spraying grain stores is never wasted. Before starting out, however, it’s important to check you are applying the correct pesticide and wearing the right protective clothing. Up to harvest farmers will devote much expertise, cost and energy to protecting crops to achieve the best possible yield and quality. Once harvest is in the store, however, the crop protection work doesn’t stop.



As well as good store hygiene, growers need to ensure the grain is at the right moisture content and temperature to prevent the risk of pest infestation. But even with these measures it’s hard to eliminate all pests and there are estimates that more than 90% of farm-stored grain harbours at least one insect species.

What to use?

Most products are designed for treating an empty store and/or for admixing with grain during filling.

Others can be used for surface admixing, i.e. applied only to the grain in the upper – 30cm to 100cm – layer of grain. Complete admixing indicates the treatment of the entire heap (See table below).

When using a product to treat an empty store, it’s recommended a second product, with a different mode of action, is used to treat grain stored in that building. This will help prevent resistance building up in certain pests.

protective clothing when spraying grain stores

Are you qualified?

Operators must hold a PA1 as well as the correct application module to apply and use the chosen products and application methods. While many have a handheld sprayer certificate (PA6), fewer are likely to hold a PA9 for the application of smokes or PA12 for products to a continuous flow of material. Operators must also wear the correct protective clothing and mask.

The correct qualification to buy specific products is required and, if using a contractor, you need to ensure the operator is suitably qualified.



Empty store treatment

Before making any treatments, ensure the store is completely empty of grain and all surfaces – walls, roof, floors – are thoroughly clean. The collected dust and debris must be destroyed, usually by burning.

After cleaning, stores can be treated with an insecticide, using a knapsack sprayer or hand lance fitted to a tractor sprayer. The applicator must be calibrated to apply the correct water rate for the surface being treated.

Smoke bombs, are used to treat areas that are less accessible to sprays, such as roof ledges. However, they are ineffective if used alone, as their role is to disturb insects and mites and make them move to sprayed areas.

At store filling

Applying insecticides to grain during store filling, or admixing, can protect clean grain from pest infestations. Useful in stores with a known threat, it’s a relatively straightforward process that usually involves mounting a nozzle to a grain conveyor or elevator.

It requires good grain coverage to be effective, with conveyor and elevator speeds adjusted to provide a shallow, even grain at the application point. It’s vital the applicator is calibrated to ensure flow rate (litres/min) matches the throughput (t/hr). Ultra low volume products are available, but require specialist application equipment.

Grain must be labelled as chemically treated when admixtures are used, and buyers told of treatment.

man wearing protective clothing when spraying grain stores

Always read the label of the product being used to ensure the correct Personal and Respiratory Equipment is selected for the operation being undertaken.

In store treatment

Pest infestations in stored grain are much harder to control. If the crop was not treated at store loading it could be removed and reloaded to apply the treatment, but only one product treatment can be applied per batch. Alternatively, diatomaceous earth can be applied as a surface admixture after filling the store.

Serious infestations can be treated with a fumigant applied to grain which must be applied by specialist contractors.


Record keeping

Farm assurance schemes require farmers and growers to have a plan for the protection of stored grains and oilseeds, and to record the actions taken to protect any stored crops.

Personal and Respiratory protective equipment required for application of insecticides for grain storage:


Operation Active Ingredient Personal Protective Equipment* Respiratory Protective Equipment*


Liquid treatments

Pirimiphos-methyl, Chlorpyrifos-methyl Coveralls, Gloves (Acetyl nitrile) and Wellington boots.

Face shield advised or required for applications and handling concentrates (mixing & filling).

Deltamethrin Coveralls, Gloves (Acetyl nitrile) and Wellington boots. Face shield required for handling concentrate (mixing & filling). Half or full face mask to at least EN 140 with a combination filter to EN 141 A1P2 as a minimum.
Smoke treatments Pirimiphos-methyl Coveralls, Gloves (Acetyl nitrile) and Wellington boots. Half or full face mask to at least EN 140 with a particulate filter to EN 143 P3 as a minimum.
Diatomaceous earth                      – Although chemically inert, taking precautions against dust is needed. Operators must wear eye protection and dust mask. Mask to EN 149 FFP2 of Half mask DIN 58 646 HM.

NOTE: * = Always undertake a site specific risk assessment and the read product label.

Insecticides approved for use in crop stores and stored crops.


Active Ingredients Formulation Empty store treatment Surface Admixture Complete Admixture
Chlorpyrifos-methyl Liquid           √           √           √
Deltamethrin Liquid           √           √           √
ULV#           x           √           √
Diatomaceous earth Dust           √           √           x
Pirimiphos-methyl Smoke           √           x           x
Liquid           x           √           √

NOTE:   √ = Approved Use,  x = Not approved, # = Ultra Low Volume.  Above information from product labels

Operator certification requirements and equipment used in crop storage:


  NPTC Qualification required Example Equipment for Treatment
Empty store treatment (Liquid) PA6a Knapsack sprayer, with extending lance for increased reach.
Empty store treatment (Smoke) PA9* Smoke generators.
Complete or Surface Admixture to grain (Liquid or ULV). PA12 Nozzle# fitted to conveyor or foot of elevator where continuous flow of grain falls.
Diatomaceous earth None required as registered as a food additive. Pepper pot or similar applying 200-600 grams per m2. Raked into top 30 cm of bulk.

*Only smoke component required. # = Example liquid nozzle: Teejet orifice plate 4916 series.

Need NRoSO or BASIS points?

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Each online course comprises a series of ‘lessons’ with some reading and/or a video to watch, followed by a multiple choice set of questions which you can sit as many times as you like. Once passed, we’ll send your points across to NRoSO/BASIS for you, so you don’t have to.


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