Endophytic fungi show activity against brown stink bugs

Brazilian researchers evaluated the potential of two native endophytic fungal isolates in managing the brown stink bug (Euschistus heros) in soybeans. The study tested Trichoderma asperelloides SF001 and Beauveria bassiana SF002 under controlled conditions. Both microorganisms increased adult insect mortality and also altered enzymes linked to plant defense (DOI 10.1016/j.cropro.2026.107762).

The research indicates 58 percent control for Trichoderma asperelloides SF001 and 46 percent control for Beauveria bassiana SF002 against adult Euschistus heros. Mortality in the untreated control group reached 48 percent. Treatment with SF001 achieved 78 percent mortality. Treatment with SF002 achieved 72 percent. The trial lasted seven days after application.

Research format

The researchers used fermented broths of the two fungi. Applications against adult Euschistus heros were carried out in containers with ten insects and commercial soybean pods as food. The volume of broth corresponded to 100 liters per hectare. The treatments with the fungi used 0,350 liters per hectare of fermented broth. The trial had five replicates per treatment.

Chitinolytic activity

Analysis of chitinolytic activity showed differences between the isolates. Beauveria bassiana SF002 exhibited almost twice the chitinase activity compared to Trichoderma asperelloides SF001. This result was consistent with the cuticle degradation assay of the stink bug. The fermented broth of SF002 also promoted greater in vitro cuticle degradation.

Despite lower chitinase activity, SF001 also degraded the cuticle and increased insect mortality. According to the researchers, other mechanisms may contribute to this action. Metabolomic analysis by UHPLC-Q-TOF showed distinct chemical profiles among the fungi.

The fermented broth of Trichoderma asperelloides SF001 yielded 15 identified compounds. Among them were peptaibols, mainly derivatives of asperellins and trichotoxins. Indole compounds and metabolites from other classes also appeared. The broth of Beauveria bassiana SF002 yielded ten identified compounds, including cyclic peptides and cyclodepsipeptides, as well as indole compounds and other metabolites.

Foliar application

In soybeans, researchers evaluated the foliar application of fermented broths on plants at the V5–V6 growth stage. The experiment used the Brasmax Lótus IPRO cultivar in four-liter pots. Treatments included water, SF001, SF002, and a mixture of the two broths in a one-to-one ratio.

The analyses measured peroxidase, polyphenol oxidase, and phenylalanine ammonia-lyase activities seven and 15 days after application. These enzymes participate in pathways associated with plant defense, phenol metabolism, and cell wall reinforcement.

The combination of SF001 and SF002 increased enzymatic responses compared to individual applications, with effects lasting up to 15 days after treatment. For peroxidase, the interaction between the fungi appeared at seven days and remained at 15 days. For phenylalanine ammonia-lyase, the two fungi showed individual effects at seven days, while the interaction between them became significant at 15 days. For polyphenol oxidase, the interaction also became evident at 15 days.

Physiological responses

The researchers interpret these results as indicating physiological responses in soybeans not predicted by the isolated action of each fungus. The study does not attribute the effects to specific metabolites, as the assays used whole fermented broths, not purified compounds.

The data support the potential of a consortium with Trichoderma asperelloides SF001 and Beauveria bassiana SF002 as a component of integrated strategies against Euschistus heros. The work points to the need for field studies, compatibility assessments with integrated pest management programs, and the development of stable formulations before practical use in soybean production systems.

This work was developed by João Arthur dos Santos Oliveira, Natieli Jenifer Mateus Corniani, Erika Fritegotto Leite, Livian Yumi Iwaoka, Giovana Gomes Ferreira Matos, Gabriela Bissoli Silva, Luana Thais Varize Marcusso, Carlos Augusto Corniani da Silva, and Willian Martire Marcusso.