Maize ranks as the 3rd most economically valuable cereal crop worldwide but its productivity is under severe threat by an invasive pest, Spodoptera frugiperda (Lepidoptera: Noctuidae). The 3rd instar S. frugiperda larvae are most damaging stage of lifecycle, that's why the present study is planned to evaluate the impacts of silicon dioxide (SiO2), potassium silicate (K2SiO3), and sodium silicate (Na2SiO3) @ 400 and 800 ppm against the 3rd instar larvae of S. frugiperda by using two application methods (soil drenching and foliar spray). Moreover, the impact of Si supplementation on biological parameters (pupation, adult emergence, and egg laying) was also recorded. The findings showed that SiO2 application through foliar spray @ 800 ppm concentration caused maximum mortality (12-36%) followed by K2SiO3 (8-32%) and Na2SiO3 (4-24%). The soil drenching method of silicon application was less effective in comparison to foliar spray. The surviving larvae showed negative impacts on growth and development, including pupation (48, 52, and 60%), adult emergence (41.67, 46.15, and 53.33%) and fecundity (46.20, 52.60, and 54.20) by SiO2, K2SiO3 and Na2SiO3 foliar spray @ 800 ppm respectively. The present study revealed that Si had a significant detrimental impact on immature stages of S. frugiperda. Consequently, Si treatment can reduce S. frugiperda reproduction which may ultimately decrease S. frugiperda establishment and early harm in maize. Silicon applications may offer a sustainable way to lessen S. frugiperda infestations, improving maize protection and lowering the need for conventional insecticides.

Miscanthus x giganteus is often considered as a suitable plant species for phytomanagement of heavy metal polluted sites. Nevertheless, its physiological behavior in response to the level of metal toxicity throughout the growing season remains poorly documented. Miscanthus x giganteus was cultivated on three sites in Belgium (BSJ: non-polluted control; CAR: slightly contaminated; VM strongly polluted by Cd, Pb, Cu, Zn, Ni and As). The presence of Miscanthus improved soil biological parameters assessed by measurement of enzyme activity and basal soil respiration on the three considered sites, although to a lower level on VM site. Heavy metal accumulation in the shoot was already recorded in spring. It displayed a contrasting distribution in the summer leaves since heavy metals and As metalloid accumulated mainly in the older leaves of CAR plants while showing a uniform distribution among leaves of different ages in VM plants. Comparatively to plants growing on BSJ, net photosynthesis decreased in plants growing on CAR and VM sites. The recorded decrease was mainly related to stomatal factors in CAR plants (decrease in stomatal conductance and in Ci) but to non-stomatal factors such as decrease in carboxylation efficiency and non-photochemical quenching in VM plants. Stomata remained open in VM plants which presented lower instantaneous and intrinsic water use efficiencies than CAR and BSJ plants. High proportions of heavy metals accumulated in CAR plants were bound to the cell wall fraction while the soluble and organelle-rich fractions were proportionally higher in VM plants, leading to a decrease in cell viability and cell membrane damages. It is concluded that not only the intensity but also the nature of physiological responses in Miscanthus x giganteus may drastically differ depending on the pollution level.