Silica and Selenium Nanoparticles Attract or Repel Scale Insects by Altering Physicochemical Leaf Traits

Area of Science:

• Agricultural Science
• Nanotechnology
• Entomology
• Plant Physiology

Background:

• Nanoparticles offer potential as agricultural alternatives, but their impact on insect behavior and plant physiology is not well understood.
• Limited research exists on how foliar application of nanoparticles affects herbivorous insects and plant physicochemical properties.

Purpose of the Study:

• To investigate the effects of nano-silica (SiO2NPs), nano-selenium (SeNPs), and bulk silica (SiO2) on the behavior of arrowhead scale insects on mandarin orange plants.
• To quantify changes in leaf chemistry (SiO2, SeO2, Ca, C content) and physical properties (toughness) following nanoparticle treatments.
• To correlate these changes with scale insect density and body size.

Main Methods:

• Foliar application of SiO2NPs, SeNPs, and bulk SiO2 to one leaf of a pair, with the other leaf serving as a water-treated control.
• Quantification of elemental content (SiO2, SeO2, Ca, C) in leaf epidermis and mesophyll using Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM-EDX).
• Measurement of leaf toughness, and arrowhead scale insect density and body size.

Main Results:

• First-instar nymphs preferred silica-treated leaves and avoided SeNP-treated leaves.
• Silica-treated leaves showed increased toughness, correlated with mesophyll SiO2 content. Insect density increased with leaf toughness and SiO2 content.
• SeNP-treated leaves did not exhibit increased toughness, and SeO2 content showed no correlation with insect density.

Conclusions:

• Nano-selenium (SeNPs) show potential as an insect deterrent in agricultural applications.
• Silica, particularly in bulk form, can enhance leaf toughness and attract scale insects, suggesting a dual role depending on the nanoparticle type.
• Understanding nanoparticle-plant-insect interactions is crucial for developing novel pest management strategies.