Protectant Choice

Grain protectants

The use of protectants, combined with meticulous hygiene and aeration cooling, is especially useful to prevent pest incursions in unsealable storages, where effective fumigation is not possible (Protectant options are limited in Western Australia, check label registration before purchasing and applying)

Always check with potential grain buyers before applying protectants as some markets do not accept any chemical residues on grain.

Grain protectants are designed to prevent pest infestations, not to control an existing insect infestation. Apply only to clean, pest-free grain.

In order to give protectants the best chance to defend stored grain, combine their use with meticulous storage hygiene practices before and after harvest.

Cleaning up the storage site and the harvesting equipment removes harbours where pests can survive, ready to infest the new season’s grain. The addition of aeration cooling also provides an unattractive environment for pests in stored grain.

Protectant choice

Always read the chemical label before choosing a protectant to ensure it is registered for use on the grain you wish to apply it to and will target the main insects commonly found in your storage. As a general guide, most protectants are only registered for use on cereal grains.

Protectant trade names vary but the primary chemistry’s which should be rotated each year or two to prevent resistance are Spinosad (which will have s-Methoprene included) or Deltamethrin. Either of these options are affective against four of the five main insect pests – Lesser grain borer, Saw-toothed grain beetle, Rust red flour beetle and Flat grain beetle for up to nine months.

To include protection against the Rice weevil, Fenitrothion or Chlorpyrifos-methyl will need to be included or added to the mix, depending on the grain type, withholding period and market acceptance.

Fenitrothion would be the choice for application on malt barley, rice or maize but be aware of the 90 day withholding period if applied at the higher rate for nine-month protection. For application on other cereals, Chlorpyrifos-methyl has the flexibility of no withholding period but is not accepted by some export markets so is often chosen for domestic or own use feed cereals.

Some protectant manufacturers offer pre-mixed options that include; Spinosad with Fenitrothion or Chlorpyrifos-methyl; or Deltamethrin with Fenitrothion or Chlorpyrifos-methyl. If the chosen chemistries are available pre-mixed, that makes mixing at application time one step simpler.

Always check if the intended grain buyer accepts the chosen protectants, read and follow product label directions and apply a chemistry only once to a parcel of grain. (Note: This is a guide only and protectant choice and application is limited in Western Australia)

Protectant application

For even protectant coating of the grain, best results are achieved with one, or even better with two, flat fan nozzles mounted to spray into the auger as the grain is loaded into storage. Mixing 1 L/t is not easy and relies on agitation as the grain passes up the auger.

Applying protectants in a belt conveyor does not provide adequate mixing and even coating. Spray can also cause issues with the belt slipping on drive rollers. Some conveyor manufacturers offer a separate application kit — ensure it can apply the protectant evenly to the stream of grain and includes agitation to mix the product through the grain.

Some protectants start deteriorating 48 hours after being mixed with water so avoid leaving for long periods before applying to grain. The product label will also indicate the anticipated effective life of the protectant on the grain, generally three months but up to nine months in some applications.

The effective life of protectants is shortened if applied to grain above 12 per cent moisture content (MC) and above 27°C or is exposed to direct sunlight, such as the end of a shed or an open bunker.

Key components for protectant application systems

• Pump delivery to match auger capacity at 1 L/t plus 10% recirculation
• Bypass line for recirculation and shutoff relief
• Flow regulator or variable position tap
• Flow meter
• Pressure gauge
• Filter
• Flan fan nozzle(s) that are easily removable for checking and cleaning
• Non-return valve to stop syphoning or dribbling once lines are primed

Maximum residue limits (MRLs)

As grain markets have become less tolerant to protectants and maximum residue limits (MRLs) are monitored scrupulously, accurate application is essential.

Some of the protectants, even if used at the recommended label rate, are right close to the MRL leaving no room for error in applying the correct rate and even spread. Commodity vendor declarations are also used in many cases to ensure a parcel of grain is only subjected to one application of the protectant to avoid exceeding the MRL. Brief training or stewardship programs are often required prior to purchasing protectants, to ensure proper use is understood and grain marketing is not compromised by misuse