The combined effect of herbicide and Bacillus thuringiensis exposure delays development in the red flour beetle

• Published in: Journal of invertebrate pathology 2024-11, Vol.207, p.108227, Article 108227
• Main Authors: Luigia Vommaro, Maria, Korša, Ana, Sofia Lindeza, Ana, Giglio, Anita, Kurtz, Joachim
• Format: Article
• Language: English
• Subjects: Aniline Compounds; Animals; antimicrobial peptides; Bacillus thuringiensis; bacteria; body condition; Dinitroaniline; Eco-immunology; Eco-toxicology; entomopathogens; herbicides; Herbicides - pharmacology; Host-pathogen interaction; human health; humans; invertebrates; Larva - drug effects; Larva - growth & development; Larva - microbiology; larvae; larval development; life history; Life-history trait; maximum residue limits; Pupation; soil; survival rate; Tribolium - drug effects; Tribolium - growth & development; Tribolium castaneum
• ISSN: 0022-2011; 1096-0805; 1096-0805
• DOI: 10.1016/j.jip.2024.108227

[Display omitted] •Pendimethalin-based herbicide (PND) is harmful to a non-target organism, T. castaneum.•Exposure to field rates and residues in soil and food elicit non-dose-dependent effects.•PND alters vulnerability to the pathogen B. thuringensis (Bt) and affects antimicriobial peptide expression.•Exposure to both PND and Bt in the larval stage affects adults, suggesting long-term effects. The use of herbicides and their long persistence in the environment have raised concerns about potential harm to ecosystems and human health. However, there is a gap in the knowledge regarding the effects of continuous exposure to residues or admitted field doses on non-target organisms such as insects that inhabit croplands and play key ecological roles. Furthermore, the potential impact of this exposure on host-pathogen interactions remains largely unstudied. This study adopted an eco-immunological perspective, investigating the influence of herbicides on an organism’s interaction with natural pathogens. The impact of this combination of multiple stressors was studied in larvae of the red flour beetle, Tribolium castaneum Herbst, 1797, previously treated with a pendimethalin-based commercial formulation (PND) and exposed to the natural entomopathogen Bacillus thuringiensis (1x109, 1x1010 cells/mL). The effects of three PND concentrations (i.e. a recommended field rate, a soil contaminant concentration and the maximum residue limit admitted in grain in EU countries: 4L/ha, 13 and 0.05 ppm, respectively) on life history traits such as developmental time, pupation rate and survival rate and the expression levels of antimicrobial peptides (AMPs) were assessed. The results showed that even at doses considered safe for human consumption or field application, exposure to PND had an impact on beetle larvae, affecting their vulnerability to B. thuringiensis. The combined experience of exposure to PND and B. thuringiensis at the larval stage resulted in a delay of larval development, a reduction in the number of pupae and emerging adults, and alterations in their body condition. Moreover, changes in the expression levels of the analysed AMPs, including Attacin 1, Defensin 2 and Coleoptericin 2, were recorded as markers for immune activity against the bacterium. The findings of this study highlight the general need for further studies on the effects of commonly used herbicides on the physiology of non-target organisms and on host-pathogen interactions at the community level.