Author(s): Ingrid K Haugland, Lars H Bjerke and Maja E Solberg

Abstract: Essential oils (EOs) are attractive candidates for sustainable pest management, yet their inherent compositional variability has limited reproducibility and slowed regulatory acceptance. This study implements an end-to-end standardization and quality-control (QC) framework that links EO chemistry to bioefficacy and stability. Identity and authenticity were anchored to ISO vocabularies and chromatographic profile standards, with GC-FID/GC-MS fingerprints, retention-index confirmation, and chemometric similarity thresholds defining batch acceptance. Targeted assays for chemotype-specific markers were validated for linearity, precision, accuracy, and robustness; principal-component analysis verified batch comparability. Bioassays covered spatial repellency against Leptinotarsa decemlineata and contact/fumigant toxicity in stored-product pests. Formulation studies compared neat oils with nanoemulsions under accelerated and real-time storage using stability-indicating tests. All lots met acceptance windows for principal markers (e.g., 1, 8-cineole in Eucalyptus globulus, linalool in Lavandula angustifolia), with library spectra and retention indices concordant. Validated methods showed R² > 0.995, recovery 95-105%, and repeatability RSD < 2.5%. Repellency rose monotonically with dose and approached a synthetic benchmark at the highest level; probit models yielded low RC50 values, indicating high potency. Contact and fumigant assays produced statistically distinct LC50s across oils and species, confirming route- and pest-specific performance. Nanoemulsions preserved >90% of key markers over three months at 40 °C/75% RH and showed superior physical integrity versus neat oils. Pilot non-target screens suggested minimal acute effects under conservative exposures. Collectively, results demonstrate that chemotype-anchored fingerprints, dual acceptance criteria (marker limits plus multivariate similarity), validated analytics, and stability-forward formulations convert variability from a liability into a managed parameter. The framework provides dossier-grade evidence for product identity, quality, efficacy, and shelf-life, and offers a practical pathway to integrate standardized EOs into integrated pest management and modern regulatory paradigms.