Early Soybean Pest Care

Initial soybean pests are those organisms that attack the crop during the seed germination stages up to approximately 30 days after emergence. These organisms are arthropods that damage the initial stages of crop development, and can negatively affect the stand, vigor, uniformity of plants as well as the crop's grain yield.

Cultivating soybeans in the direct planting system (SPD) brings numerous advantages when compared to the traditional cultivation system. However, SPD favors the development of initial pests such as soil pests in the crop, since the soil is not disturbed with a harrow and/or plow. Damage caused by corós in soybeans results from the consumption of roots or even nodules of biological nitrogen fixation, resulting in a reduction in the plants' ability to absorb water and nutrients from the soil and atmospheric nitrogen, through biological fixation. The intensity of coró damage is greater in young plants under water deficit conditions. Plants attacked by corós show delayed development, followed by yellowing, wilting and death. In conditions of high infestation in the soil, 100% crop loss may occur, especially when the larvae are more developed. Damage from brown stink bugs occurs as a result of the continuous sucking of plant roots, which can cause yellowing, underdevelopment and even death. Crops attacked by brown stink bugs have different degrees of susceptibility, with cotton being the most susceptible, followed by soybeans, corn, sorghum and rice.

The occurrence of initial pests that attack the aerial part of soybean plants is generally associated with the soybean precursor crop. In this group of pests we can mention the occurrence of Spodoptera frugiperda caterpillars, slugs, snails and the soy anteater.

Vegetation cover, intended for the production of straw in the SPD (e.g. oats, wheat and brachiaria), can promote the development of high populations of caterpillars of the species Spodoptera frugiperda, especially in the driest periods of the year. The caterpillars of this species can cut soybean seedlings close to the ground or feed on their foliage, which can cause their death and, consequently, a reduction in the soybean stand. However, managing this pest in the SPD is possible when using the correct technology and at the right time.

Slugs and snails are molluscs of the Gastropoda class and occur, most frequently, in humid and cool environments. These pests are more abundant in soils with a greater amount of straw and organic matter, as observed in the SPD. Both slugs and snails feed on the cotyledons, stem and leaflets of newly emerged soybean seedlings, with injuries similar to those caused by insects, which can destroy the apical portion and cause death, thus reducing the crop's stand. . The soybean anteater is a species in which adults and larvae can cause damage to the crop. The adults scrape and shred the tissues of the main stem of the soybean and, eventually, the lateral branches and petioles of the leaves, while the larvae are endophytic, that is, they feed inside the main stem, more precisely the pith.

Control of initial soybean pests is carried out through seed treatment or spraying, applied to the sowing furrow or to the aerial part of soybean plants. The control of corós and soybean anteaters can be carried out efficiently through the use of neonicotinoid insecticides applied to the seeds. As for the brown stink bug, the best control alternative is the spraying of insecticides in the sowing furrow or through the cultivation of covers, in succession or rotation, which are unsuitable for the development of the insect, such as sunn hemp. S. frugiperda caterpillars, slugs and snails can be controlled by spraying insecticides on soybean plants.

Credit José Ávila, Embrapa Researcher