Soy is considered the main agricultural commodity produced in Brazil, and plays an important role for the country and in Brazilian exports. During its cultivation, several pests can negatively affect the crop, through losses and increased production costs, damaging grain productivity.
Among the main insects/pests that cause economic damage to soybean crops in different periods of their development, the brown stink bug (Euschistus heros) stands out. This insect damages soybeans from the vegetative stage to the maturation of the grains, reaching the seeds by introducing its mouthparts into the pods, leaving the seeds wrinkled and weak, and, consequently, damaging the quality and mass of the grains. Furthermore, it can be a gateway for fungal diseases to settle in the grains, causing irreversible physiological disorders.
Symptoms
If affected by this insect pest, soybeans may present symptoms such as leaf retention, which causes an increase in grain moisture, damaging the harvest. Furthermore, during off-season periods, the stink bug survives by feeding on other host plants, remaining there until the next implementation of the soybean crop.
Another symptom of the presence of the pest in soybeans is the pods aborting, thus delaying maturation and decreasing in size, forming lesions on the grains.
Identification of the brown stink bug
Identification of the pest is an important step in brown stink bug control. The adult insect is dark brown in color, with two lateral elongations of the pronotum in the form of spines and a white crescent at the end of the scutellum. During the summer, these extensions stand out with a stronger color than in winter.
Management and forms of control
To manage the stink bug in the crop, it is necessary to monitor the pest, which must be carried out weekly from the flowering period onwards. The stink bug count is carried out using a beating cloth, which is one of the most effective monitoring methods, with the presence of two stink bugs per sampling for soybean crops intended for grain and one stink bug for soybean crops for grain being considered a control level. seed. This way, it is possible to align the best form of application and the correct time to carry it out.
Bedbug control should preferably be carried out in a way that enhances integrated pest management. In relation to chemical control, the application of insecticides with shock action must be done during the critical period of control in soybeans, which begins at the R3 stage, as it is at this moment that pod development occurs. This critical period can extend until the R7 stage, when physiological maturation occurs. If the infestation occurs before the R3 stage, the pressure of this pest must be reduced by anticipating the application.
For control, the mixture of pyrethroids with neonicotinoids has shown good results. It is worth highlighting that, to achieve satisfactory controls, it is necessary to follow the correct technical recommendations and apply them under favorable environmental conditions.
An alternative control strategy is the use of trap plants, such as the adoption of borders that present an early cycle for initial management of the pest, reducing concentration and pressure within the area.
It is also worth remembering that bed bugs have many natural enemies, such as the parasitoids Trissolcus basalis and Telenomus podisi. In this case, the producer can preserve them on his farm and, preferably, use more selective insecticides, as these natural enemies parasitize eggs of different species of bed bugs and contribute to the population reduction of this pest.
Controlling the brown stink bug is still a challenge in agriculture, but with adequate monitoring of the insect, combined with biological alternatives, it is possible to reduce the pest's attack, preserving soybean productivity.
Text written by Bianca Carolina Bariquelo and Vitória Hedwiges Bender Carlson, members of AGR Jr. Consultoria Agronômica, Junior Company of the Agronomy Course at UFSM Campus Frederico Westphalen, under the guidance of professor Dr. Gizelli Moiano de Paula.
