Storage pests can cause loss of up to 10% of Brazilian grain stocks

Feared by food producers, pests such as the grain weevil and the tobacco beetle are a serious problem that directly affects storage after harvest. According to data from the Ministry of Agriculture (Mapa) and the Food and Agriculture Organization (FAO) of the United Nations (UN), annual losses in stored grains in Brazil can reach 10%.

“In addition to the loss in quantity, we need to consider the qualitative losses, which can compromise all the grains produced or classify them with lower added value”, observes the Regulatory Affairs manager of the National Union of the Plant Protection Products Industry (Sindiveg), Fábio Kagi.

With this in mind, it is very important that rural producers follow some integrated pest management protocols to avoid the problem by knowing the behavior of each pest, divided into primary and secondary.

“Primary pests attack whole or healthy grains, as they pierce the grain and feed on the inside – which allows them to develop and complete their life cycle – and on the outside, causing economic damage. Secondary pests, on the other hand, occur in low populations, and therefore rarely cause economic damage or require control measures,” explains Fábio.

According to the professional, the pests that most affect national grain storage are the cereal weevil (sitophilus zeamais) – a species of beetle also known as the cereal weevil (Rhyzopertha dominica), rice (sitophilus oryzae) and corn (S. zeamais) –, the brown beetle (Tribolium castaneum); the tobacco beetle (Lasioderma serricorne) and the grain moth (Ephestia kuehniella).

“The weevil is considered the main storage pest of wheat, but it can also attack barley, triticale, rice and oats, as well as rice and corn. They are very similar species and can occur together in the mass of grains or seeds of wheat, corn, rice, barley and triticale, both in the field and in the warehouse,” explains the manager. “The brown beetle attacks all types of ground cereals, such as bran, feed, flour, cornmeal and broken grains, defective grains or grains already attacked by other pests, as well as ginger roots, dried fruits, chocolate, nuts and leguminous grains, causing them to deteriorate and resulting in losses to production,” he adds.

In soybeans, in particular, a very common occurrence is the tobacco beetle. The insect is known for piercing seeds and grains and, consequently, affecting the quality of the product.

“Regardless of the pest, it is essential that the producer understands and identifies what can cause it to proliferate and affect the quality of the grains and production as a whole. This way, he can choose and implement the most efficient control measure aligned with the pest in question,” emphasizes Kagi. 

Cleaning and fumigation

Before receiving new shipments each harvest, it is essential that grain and seed storage units are clean and free of insects, mites, fungi and rodents. Other points to be observed are the existence of ventilation and the appropriate temperature and relative humidity conditions for receiving the crops.

In addition to cleaning, fumigation of the space, as Kagi explains, can be done preventively with inorganic insecticides based on aluminum phosphide – a precursor to phosphine – which act in all stages of the insect's development and have good penetration in places inaccessible to spraying.

According to the Sindiveg manager, during the fumigation process, heat and relative humidity accelerate the release of phosphine, while the opposite occurs in cold and dry air. “The exposure time of the product varies according to the environmental conditions during application. Thus, a temperature of 25℃ is ideal for carrying out the process,” he highlights.

The dose to be applied is measured according to the volume of the grain batch/silo and the target pest. If the silo is full of grain, in curative applications, it is recommended to level the surface where the tablets will be deposited before carrying out the fumigation to facilitate sealing with tarpaulin and prevent gas escape.

“The initiative, carried out with protective equipment, highlights the necessary care for controlling different pests, reinforcing the importance of maintaining the quality of grains and delivering healthy food with all its characteristics and benefits preserved,” he concludes.