Résumé
The cotton aphid (Aphis gossypii), is a polyphagous species that transmits phytoviruses. It is one of the most damaging and widespread insect pests in pomegranate orchards worldwide, including countries of the Mediterranean basin such as Algeria. The control of its populations mainly relies on synthetic pesticides although safer alternatives, such as botanical insecticides, warrant further exploration. This study investigated the aphicidal potential of the essential oil (EO) of Santolina africana leaves (Asteraceae), widespread North African shrub, against A. gossypii populations under laboratory conditions. The EO phytochemical profile was determined by GC/MS. The 49 compounds identified were mainly oxygenated sesquiterpenes and monoterpenes, with artemisia ketone (22.69%) and longiverbenone (16.55%) as the dominant compounds. The toxicity of the EO was tested at five concentrations (0.1–1.6%, v/v) through topical contact and fumigation bioassays across seven exposure times (2–72 h). Each bioassay involved a population of 25 aphids with five replicates, totalling 750 individuals per method. Mortality was both concentration- and time-dependent, reaching 100% within 12 h under fumigation. After 24 h, fumigation required EO concentrations 3.6 and 36 times lower than topical application to achieve LC₅₀ and LC₉₀ values, respectively. This study provides the first evidence of the strong biocidal activity of S. africana leaf EO against A. gossypii populations, highlighting its potential for pest populations and for reducing the spread of the phytoviruses transmitted by this aphid.