2021/22 harvest requires caution with brown stink bugs and green belly

Harvest season comes and season ends, and rural producers must always be aware of the incidence of pests and diseases in crops. Stink bugs should be on the care agenda, as the problem, especially in soybeans, occurs every year and causes direct damage, with attacks on pods and grains. In the state of Mato Grosso, the species Euschistus heros – brown stink bug is more abundant in the culture, however, in recent years, the species Diceraeus melacanthus – green belly bug has occurred in high populations since the beginning of plant development.

This will be one of the topics highlighted during one of the stages of Fundação MT in Campo Safra, in Nova Mutum-MT. The event, which takes place on January 27th, is held by the Mato Grosso Agricultural Research Support Foundation at the institution's Learning and Dissemination Center (CAD), in this city.

According to entomology researcher Dr. Lúcia Vivan, the predominance of one of these species varies depending on the location, climate, cultivars and the stage and development of the crop. “Similarly, the extent of the damage depends, among other factors, on the stage of development of the plants during the infestation period, as this occurs from the vegetative stage onwards”, she reports. After this period, they progressively increase in the reproductive phase, with exponential and accelerated growth at the end of the crop cycle, especially in mid- and late-cycle cultivars.

Big losses

When stink bugs attack pods, losses can reach values ​​exceeding 30%. “If the attack occurs during the granation phase, deformations, wilting and stains may appear on the grains. In this case, they lose their commercial value due to their reduced oil content”, explains the entomologist.

Losses in seed germination power can exceed 50%, in addition to a drop in vigor. Infestation during the seed development phase makes them small, wrinkled and deformed. “When stink bugs attack grains, there is a loss in the quality of grains and seeds, mainly due to the inoculation of the fungus Nematospora corylii, which causes yeast spot, also known as yeast spot”, details Lúcia.

Impact on corn

When we talk about the green-bellied stink bug, care begins with the soybean crop, which serves as food and protection for this insect, increasing its population and remaining in the area, where it will attack the corn crop. “The cereal will be susceptible to this bug a few days after emergence, which can kill the seedling or the apical bud, generating tillering. Depending on the attack, some sheets of the cartridge are unable to unroll, causing them to become clogged”, reports the researcher from Fundação MT.

Therefore, it is important to carry out seed treatment in corn crops, and foliar sprays 3 to 5 days after emergence and repeat the application 7 to 10 days after emergence. “Corn is susceptible to attack by this insect until the stage V4-V5. Also applying it to straw after soybean harvesting can be a strategy to reduce the population that will remain in the area. Another important point of study is spraying in the plant and apply form, in which insecticide is applied immediately after planting corn”, adds Lúcia.

Management is essential in both cases

Whether for one bed bug or another, it is essential to carry out correct management. For the brown species, it is recommended to monitor the areas to identify the moment when the insect enters the crops. “Based on this, control must be carried out and the development of the population must be monitored from the beginning, in order to not generate high populations for later areas. On average, between 1 and 2 stink bugs/m are used to carry out control in grain production areas, for seed areas the level has been 0,5 stink bugs/m”, details the entomologist.

For the green belly bug, management must be done within the production system, taking care of the population throughout the year, as it has many host plants. It is worth remembering that areas with the presence of weeds will favor the development of this pest, offering food and places for oviposition. Thus, fallow areas have a high probability of maintaining populations.

When planting soybeans, it is important to evaluate the straw and check for the presence of the insect. In this case, you can opt for pre-planting soybean desiccation and use of seed treatment focusing on suckers. “During the development of soybeans, it is important to monitor this species as well, however, as its habit is more low-lying and is under the straw, this can make it difficult to quantify the population”, reinforces Lúcia.

For more information about bed bugs, click here.