Bio-selenium nanoparticles for citrus red mite pest management

Overview

The citrus red mite (Panonychus citri) is one of the most destructive pests in citrus production worldwide, causing significant annual yield losses. It is difficult to manage because of its high reproductive rate, broad host range (including citrus, rose, and pear), and its rapid development of resistance to many registered acaricides. This proposal introduces an alternative pest management approach based on biologically synthesized selenium nanoparticles (Bio-SeNPs) applied as a foliar spray. Rather than acting as a direct toxicant, the Bio-SeNP treatment is designed to stimulate the plant's own defense metabolism, making the host less palatable or less suitable for the pest.

Technical specifications

Mechanism of action:

• Bio-SeNPs are applied at low concentrations (proposed range 5–50 ppm) as a foliar spray on stems and leaves
• The treatment activates phenylpropane and branched-chain fatty acid metabolic pathways
• It upregulates AT3-related enzymes and gene expressions, boosting synthesis of flavonoids, total phenols, and other secondary metabolites
• The treatment promotes phyto-hormone synthesis genes, increasing jasmonic acid, abscisic acid, and salicylic acid levels
• In cereals, Bio-SeNPs have been shown to raise DIMBOA and jasmonic acid levels, increase flavonoid analogues (luteolin, apigenin, rutin), and elevate glutathione peroxidase
• Observed effect on pests: a 30% reduction in Sitobion avenae populations on wheat after low-concentration Se treatment, linked to changes in plant composition and palatability

Proposed validation design:

• Field trials in Guilin, Guangxi Province, a major citrus-producing region of China
• Four Bio-SeNP concentrations tested (5, 10, 20, and 50 ppm)
• Three spray applications at 10-day intervals
• Pest population counts measured at days 5, 10, 20, 30, and 40 post-application
• Secondary metabolite, plant hormone, enzyme, and signaling pathway changes tracked over time
• Mechanism of palatability change investigated through metabolomics and genomics

Technology readiness level

The Bio-SeNP approach is supported by prior validation on pepper (enhanced capsaicinoid, flavonoid, and total phenol synthesis via phenylpropane and branched-chain fatty acid pathway activation) and on wheat (raised DIMBOA, jasmonic acid, flavonoid content, and a 30% reduction in S. avenae populations). The proposed citrus red mite trial represents the next stage of validation, moving from proof-of-concept in other crops toward crop-specific efficacy data in a major commercial citrus region. The technology is at an early-to-mid research validation stage, with field-scale citrus data, metabolomics, and genomics evidence still to be generated.