Arable Lesson 3: Prevent pest trouble in store

This lesson provides advice on the safe and effective way to control a range of pests and rodents in store. It looks at how cleanliness and vigilance will provide protection, but in some cases pesticide treatments and rodenticides will be required.

It is incumbent on owners and operators to ensure they follow an integrated pest management approach, apply best practice and ensure they have the correct training and qualifications to use the appropriate products and equipment in store.

Quick Quiz: Pest problems

How well do you know your in-store pests?

All photos courtesy of the Department for Environment, Food and Rural Affairs (Defra) © Crown Copyright 2021


Prepare to beat the pests

Grain store preparation is crucial. It’s a job that must be done meticulously to ensure that grain is kept in the best possible condition, and with the most protection from insects.

  • Remove all debris and dust from the cracks and crevices in the floor, walls and roof space
  • Don’t forget to clean machinery and conveyors, because they provide ideal harbourage for pests
  • It’s essential to monitor insect activity with sticky traps inside the store
  • Ensure the building is waterproof and that all doors are well sealed to prevent rodents accessing the store
  • Ensure there will be adequate space above the grain for ventilation
  • Prevent condensation by ensuring there is adequate ventilation to extract stale, cooling air
  • Consider treating the whole store with a spray application of an approved insecticide several weeks before filling to control any active insect pests.

After thorough store cleaning and treatment (pre-storage), place insect attractant bait bags and check weekly by shaking over white paper. Take remedial action if insects are identified.

Once the store is filled with grain, pitfall insect traps can be used to detect the presence of insects. Pitfall Traps are used in pairs, with one at the surface and one placed approximately 8cm – 15cm down into the grain. The traps should be placed approximately 5m – 6m apart. 

Traps should be regularly checked and any insects found should be carefully identified and remedial action, such as cooling or fumigation, carried out as necessary.

Are you qualified?

Spraying the grain store is often a job that falls to the sprayer operator, but don’t assume you hold the correct qualification for the particular application or treatment.

As well as applying pesticides to the building, there is occasionally a need to also treat the crop itself, which also requires the correct ‘PA’ application module.

What PA do you need?


Operating pedestrian hand-held applicators fitted with hydraulic nozzles or rotary atomisers to apply pesticides to land.


Applying pesticide mists, less than 100 microns VMD indoors.


Applying pesticide fogs, less than 100 microns VMD indoors.


Applying Pesticide smokes indoors.


Applying pesticides to plant material during a continuous flow process.

Quick Quiz: Pests, what PA do I need?

Let’s check to see how well you know your PA modules for each applicator:


Do your sums

When carrying out treatments to grain in store or in a continuous flow, operators will be required to carry out calculations to assess the correct amount of product to be used.

These sums will usually need you to calculate one of the following:

  • Surface area – in the case of store ‘fabric’ treatments
  • Building volume (in the case of mists, fogs or smokes)
  • Crop flow (in the case of continuous flow treatment of grain).

Surface area

Length (m) x width (m) = surface area (m²).

This usually applies to roof, walls and floor; however, the floor and roof surface area calculations in a round silo are as follows:

 πr2 (π  = 3.142)

Example:  A round silo floor has a radius of 6m: 3.142 x (6 x 6) = 113m²

Building volume (rectangular)

Building to eaves: length (m) x width (m) x height to eaves (m) = volume (m³)

Roof area: length (m) x width (m) x eaves to apex height (m) / 2 = volume (m³)

Add both volume answers together to give you total volume of building (m³)

Building volume (round silo)

Building to eaves: πr2 x height to eaves (m) = volume (m³)

Roof area:  πr2 x eaves to apex height (m) / 3 = volume (m³)

Add both volume answers together to give you total volume of building (m³)

Crop flow

Most admix products are applied at a rate per tonne. Some products are supplied in a dilute (ready to use) form making calculating overall application rate more straightforward than products that require dilution.

Grain conveyors usually have a nominal output in t/hr and products usually have an application rate in litres/100t.

Label application rate litres per 100t/100 = application rate litres/t.

T/hr to be treated x litres/t = litres/hr

How to calculate the flowrate

Example: A grain conveyor has a rated output of 30t/hr. The product application rate is 4.2 litre/100t.

Divide 4.2 litres by 100 for the litre/t rate = 0.042

30t/hr x 0.042 litre/t = 1.260 litre/hr

Divide this by 60min for the litres/min

Therefore 1.260 divided by 60mins = 0.021 litres/min.

So, to check flow rate collect the nozzle output for three minutes (3mins x 0.021) = 0.063 litres (or 63ml).

Rodent control update

Positive changes noted in the recent report from the rodenticide regime’s Government Oversight Group show that more than 23,000 pest control technicians, gamekeepers and farmers have completed approved training courses and become certified as competent users.

There are 17 stewardship-approved farm assurance schemes whose 94,000 members are inspected against standards for rodent pest management that comply with the Campaign for Responsible Rodenticide Use (CRRU) Code of Best Practice.

Nearly 1,300 premises selling stewardship label, professional use only, rodenticides have undergone independent BASIS point-of-sale audits.

Secondary poisoning

During the first two years, even with all stewardship elements in place, there continues to be significant rodenticide residues found in Barn Owls. This is caused by ‘secondary poisoning’, which is when a predator eats a dying rodent that has been poisoned, or a scavenger eats a dead carcase of a poisoned rodent.

Secondary poisoning is the main cause of non-targets being infected by rodenticides.

The report states that government is expecting lasting reductions in rodenticide residues carried by non-target wildlife. Without good evidence of this we can anticipate more restrictions on how rodenticides can be obtained, used and by whom.

Best practice baiting

Remember the preferred order of control is habitat management, physical control and lastly, chemical control.

Quick Quiz: Pest control

Let’s check the three main control-areas:


The CRRU Code of Best Practice has a seven-point action plan for the safe use of rodenticides:

  1. Always have a planned approach
  2. Always record the quantity of bait used and where placed
  3. Always use enough baiting points
  4. Always collect and dispose of rodent bodies
  5. Never leave bait exposed to non-target animals and birds
  6. Never fail to inspect bait regularly
  7. Never leave bait down at the end of the treatment

IPM approach

To help reduce the incidents of secondary poisoning in non-targets, it’s recommended farmers should adopt an Integrated Pest Management (IPM) approach – using a variety of methods to control rodents.

IPM is not difficult. Just as out in the fields, it encourages the use of preventative measures and non-chemical control before resorting to poisons. For rodent control the best IPM approach is to use habitat management first, then physical methods to prevent the rodents from entering the building and ensuring they have no reason to stay if they do enter. Chemical control should always be the third option.

It is recommended you follow this nine-step IPM approach:

  1. Proofing buildings
  2. Hygiene
  3. Denial of food and water
  4. Removal of harbourage
  5. Trapping
  6. Alphachloralose (anaesthetic – mice only)
  7. Gassing (rats only)
  8. First Generation anticoagulants (warfarin, chlorophacinone and coumatetralyl).
  9. Second Generation anticoagulants (brodifacoum, bromadiolone, difethialone, difenacoum, flocoumafen

Well done, you have reached the end of Lesson 3 – Prevent Pest Trouble and you now need to complete the end of lesson test. You should not move on to the next lesson, until you take this test. You will need 80% to pass. You can re-sit the test as many times as it takes to pass. Once you have passed this test, you can move on to lesson 4.

To start the test, click on ATC: Arable: End of Lesson 3 Test (Compulsory) below: