Improper storage of wheat can put harvest at risk

The work to ensure the delivery of a quality product to the end consumer does not end at harvest. Proper storage of wheat is essential to avoid pests and maintain the health of the product. After choosing the cultivar carefully, managing the crop and harvesting efficiently, you also need to pay attention to the way in which the grain is stored. According to the Ministry of Agriculture (MAPA) and the Food and Agriculture Organization (FAO/UN), the average loss of grains caused by pests in warehouses in Brazil is approximately 10% of the total produced annually. When it comes to wheat, the presence of storage pests can affect both the quantity and quality of the grains, causing the batch to be disqualified from commercialization and making its use by the milling industry unfeasible.

A large group of pests attack wheat grains. The main ones are weevils, beetles and moths. According to the agronomist and coordinator of the IFRS Agronomy Course - Campus Ibirubá, Marcos Paulo Ludwig, the pest attack can cause external damage, to be observed directly, or internal damage when the pest is inside the product. He explains that recognizing the symptoms of an attack is important for identifying and verifying the damage. “Monitoring is the most appropriate way to manage pests in stored products and should preferably begin before damage appears. The beginning and interval between assessments are related to the application of preventive products, initial quality of the product, environmental conditions, storage location, cleaning and management of the facilities”, he explains. Marcos does not recommend mixing already stored grains with recently harvested grains, as this may increase contamination by pests.

Cleaning of facilities

The storage capacity of agricultural products in Brazil reached 176,5 million tons in the first half of 2020, of which 1,9 million were wheat. The information is part of the Stock Survey, released in November by the Brazilian Institute of Geography and Statistics (IBGE). Proper maintenance of storage spaces helps control the incidence of pests. According to Marcos, the first step is to clean the facilities, removing waste, dust and possible pest outbreaks. “Cleaning must begin with the silo still empty, removing leftover materials previously stored and materials accumulated in different parts of the silo, which can be done with the help of a broom and spatula. Cleaning is an important step in keeping grains free from insects, as it makes it difficult for pests to spread,” he explains.

Another important recommendation is to apply products preventively. Marcos advises: “after cleaning, it is recommended to eliminate possible pest outbreaks and apply products that make it difficult for them to enter the storage units. To ensure application in the largest storage area, application is carried out with knapsack sprayers on the walls, floor, ceiling, aeration ducts, conveyors and beams”.

Bruno Moncks, seed production manager at Biotrigo Genética, highlights another tool used as a preventive treatment in the management of pests in stored grains: thermofogging. “This is a method that does not replace traditional spraying and purging treatments, but by forming a mist it can reach difficult-to-access places, such as structures and transport machines, which are inaccessible to conventional treatments, but which are important foci of reinfestation”, explains.

control methods

If the presence of pests is identified, one of the most common methods for control is purging, using phosphine tablets. However, according to the agronomist, it is important to respect the recommended number of tablets and exposure time, and it is necessary to keep the area sealed during the period of treatment and exposure to the product. “In the case of a purge in the aeration system, it is essential to use tarpaulins to seal the engine, fan and air outlet ducts. Sealing is important to avoid losses, contamination and ensure application efficiency.” To know if the measure was effective, just look at the tablets, which must be in powder form. It is also necessary to sample and check whether pests are controlled. Furthermore, Marcos warns to be careful with the repeated use of products with the same active ingredient, which can lead to pest resistance.

Treating grains with insecticides is another control method that has the characteristics of greater residual pest control when compared to purging. According to Biotrigo's production manager, this practice consists of applying insecticides to the mass of wheat grains on ribbons or conveyor belts. “It is important to highlight that the use of this control method requires the installation of equipment for application; use of low flow rates over the grains; in addition to taking care of the withdrawal periods, which is the period of time between the treatment and commercialization of the grains that varies between active ingredients”, he recommends.

Even though wheat is already heading toward the end of the harvest in the last regions that sow wheat, monitoring is required while the grains are stored. In addition to the actual damage, one of the biggest causes of cargo refusals by mills is the presence of live insects in the cargo.