Grain weevils are insects that belong to the order Coleoptera, Sitophilus genus. Most insects of this genus are known as pests of stored grains (wheat, rice, corn) because the larvae grow and feed by consuming their interior, depreciating their value. Adult females create holes inside cereals, seeds, or nuts, where they lay their eggs and then seal the hole. The larvae grow inside, feeding on the contents, and then transform into pupae. Usually, when they turn into adults and leave the infested cereal, the inside of the grain is empty.

The most common species that cause damage to stored grains are rice weevils (Sitophilus oryzae), wheat weevils (Sitophilus granarius), and maize weevils (Sitophilus zeamais). In addition, they can penetrate inside homes through infested food, requiring control treatments.

Types of treatments for grain weevils

Because they enter indoor areas together with the infested products, in case of a positive detection, it is recommended to perform a careful inspection of all foods and to eliminate them, in case of insect presence. Uninfested food will be sealed and stored indoors. It is advisable to first perform a mechanical treatment through vacuuming, insisting on areas where they could hide, and then applying specific treatments.

Against grain weevils found indoors, it is recommended to carry out treatments using insecticides applied by spraying or with ready-made insecticides. Insecticides should not be applied to food, surfaces, or utensils that may come in contact with food.

Recommended insecticides for grain weevils:

They are biocidal substances used for treatments against grain weevils, most of which act on the insect’s nervous system. In general, they are concentrated contact insecticides that dissolve in water, according to the recommended doses. The solution is applied by spraying, using manual or motorized equipment, depending on the size of the treated space.

Recommended sprayers for the application of insecticides:

Sprayers are low-pressure applicators, used for the application of precise dose insecticides. Their capacity varies depending on the type of device, its design, the application method (manual / electric sprayers), and the size of the treated space. Special attention must be paid to the settings of the device, as well as to its maintenance.

Aerosol-type insecticides for grain weevils

Immediately following insecticide spraying, aerosol-type insecticides may be used. The released particles will irritate the weevils and cause them to come out of hiding places and come into contact with the solution applied initially. Before using the insecticide, it is recommended to close doors, windows, and the furniture must be arranged so that the substances infiltrate all the cracks. Depending on the product used, it must be left to act for a few hours, during which time the area must remain closed, according to the specifications on the label.

Recommended aerosol insecticides:

Aerosol-type insecticides act by releasing the active substance in a gaseous form and covering the entire space to be treated to ensure the penetration of the insecticide into hard-to-reach areas. They come pre-dosed and ready to use. The released particles irritate the insects, causing them to come into contact with the previously applied insecticide, therefore, in case of pests difficult to control, aerosol insecticides are used together with those applied by spraying. For optimal results, the treated room will be kept closed for at least 2 hours.

Ready-to-use insecticide treatments for grain weevils

They can be found in the form of powder, granules, liquid, and spray. Ready-to-use insecticides are applied to dry surfaces. Because they act by contact or ingestion, the targeted insects must cross the treated space. It is advisable to carefully read and follow the recommendations on the label of the product.

In hard-to-reach spaces inside or under furniture, it is recommended to use powder insecticides. They are applied to cracks and crevices where grain weevils can hide.

Recommended ready-to-use insecticides:

Ready-to-use insecticides are pre-dosed solutions and can come in several forms (spray, powder, granules, etc.). The application is made according to the treated space, taking into account the information on the product label. For optimal results, they are usually applied as close as possible to the source of infestation.

Special devices can be used for the easier application of powder products.

Recommended dispensers for the application of powder insecticides:

Dispersers are devices specially designed for the application of granular or powder (dust) products. They are used to treat hard-to-reach spaces, for example: inside walls (cracks), behind panels, spaces around electrical outlets, and very narrow spaces.

Treatments against grain weevils in silos and warehouses

Grain weevils are mainly considered pests of stored cereals, therefore, for long-term protection, it is recommended to treat the spaces where cereals are to be stored, as well as to treat the cereals before loading them in the silo/warehouse.

Cereal treatment

They are performed using specific insecticides, applied by direct spraying onto the cereal, respecting the specifications on the product label. It is recommended that the treatment of cereals on conveyors be performed with ULV with very fine particles. Otherwise, if sprayed coarsely, after they are loaded into the silos, there is a risk that they will mold.

Recommended insecticides for the control of grain weevils:

They are biocidal substances used for treatments against grain weevils, most of which act on the insect’s nervous system. They are usually ‘contact insecticides’, in the form of a concentrate that dissolves in water, according to the recommended doses.

Treatment of storage spaces

In addition to the treatment of cereals, it is also recommended to treat the storage spaces before loading them. To ensure a long-lasting treatment, it is indicated that, depending on the chosen insecticide, as well as the size of the treated space, the treatment be performed with the help of sprayers or atomizers.

Recommended insecticides for treatments of storage spaces:

They are biocidal substances used for treatments against grain weevils, most of which act on the insect’s nervous system. They usually contact insecticides, in the form of a concentrate that dissolves in water, according to the recommended doses.

Recommended sprayers for the application of insecticides:

Sprayers are low-pressure applicators, which are used for the application of precise dose insecticides. Their capacity varies depending on the type of device, its design, the application method (manual/electric sprayers), and the size of the treated space. Special attention must be paid to the settings of the device, as well as to its maintenance.

Atomizers recommended for the application of insecticides:

The atomizer is a gasoline-powered spray gun. It has a higher spray rate than regular devices.

Protective equipment

Protection equipment has the role of protecting the person performing the disinfection treatments. To avoid inhalation of vapors created during spraying or direct contact with the applied substances, it is recommended to wear a complete set of protective equipment. This includes hooded protective suits, gas masks with filters, chemical protection gloves, rubber boots, or waterproof footwear, as appropriate.

Recommended protective equipment:

Protection equipment has the role of protecting the person performing the treatments from dangerous substances. This category includes protective gloves, coveralls, masks, etc. The equipment is selected depending on the type of treatment, as well as the substances used or the targeted insects.

• Protective gloves

• Gas masks, glasses

• Chemical protection suit with hood

In conclusion, for efficient control of grain weevils, as well as for increased protection during the storage period, it is recommended to treat both the space in which the cereals are to be stored and the cereals, before loading them into storage.