Influence of mycorrhizae and silicon on maize and soybean resistance and tolerance to Spodoptera frugiperda (Lepidoptera: Noctuidae)

Productivity of soybean, Glycine max (L.) Merr. (Fabales: Fabaceae), and maize, Zea mays L. (Poales: Poaceae), is reduced by several insect pests, among the most important of which is the fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae). Control of this insect relies mainly on chemical insecticides or transgenic plants expressing Bacillus thuringiensis Berliner (Eubacteriales: Bacillaceae) proteins, but these methods impose strong selection pressure favoring resistance evolution. Soil applications of silicon (Si) and arbuscular mycorrhizal fungi (AMF) are potential alternative tactics to enhance plant resistance and tolerance within integrated pest management programs. This work evaluated the effects of soil application of Si and AMF, individually and in combination, on the development of soybean and maize and on their resistance and tolerance to S. frugiperda. Greenhouse experiments used 4 treatments: control, Si application, AMF inoculation with Rhizophagus irregularis (Błaszk., Wubet, Renker & Buscot) (Glomerales: Glomeraceae), and combined Si + AMF. AMF inoculation significantly increased root and shoot biomass of soybean and plant height in maize, while Si significantly increased root biomass in maize. The combined AMF + Si treatment significantly reduced defoliation by S. frugiperda on soybean. AMF-inoculated soybean plants also recovered better from mechanical defoliation, producing greater shoot biomass, whereas Si-treated maize showed higher root biomass after injury. These findings demonstrate that Si and AMF soil applications can enhance crop development and contribute to resistance and tolerance against fall armyworm, offering sustainable alternatives for integrated pest management in soybean and maize.