Effects of Rosmarinus officinalis and Salvia officinalis essential oils on Tetranychus urticae Koch (Acari: Tetranychidae)

•We assess the pesticidal activities of rosemary and sage essential oils.•Both essential oils caused acute contact toxicity to adult Tetranychus urticae.•Extracts decreased spider mite oviposition and larvae emergence rates.•Sage oil showed greater acaricidal activity than the rosemary extract.•These natural mixtures had no biocide effect against Ceratitis capitata. Laboratory trials were carried out to characterize Rosmarinus officinal and Salvia officinalis essential oils and to evaluate their pesticidal activities against Tetranychus urticae. Slide-dip and leaf-disk bioassays were employed to study the mortality caused by these plant oils on two-spotted spiders. Different dilutions of both essential oils (0.10–0.25%, v/v) caused acute contact toxicity, although the sage extract showed greater acaricidal activity than rosemary oil. Mortality rates of 95–100% were observed at all the sage oil dosages and when rosemary emulsions contained at least 0.20% of essential oil. In the residual contact experiments (leaf-disk assays), 0.15–0.25% of sage oil or 0.25% of rosemary extracts significantly reduced mite survival. Leaf-disk bioassays were also used to evaluate the effects of oils on T. urticae fecundity. The total number of eggs oviposited decreased as the oil dosage increased and rate reductions were significant when 0.15–0.25% of sage or 0.25% of rosemary extracts were sprayed onto leaf-disks. The effect of oil treatments on the number of emerged larvae was similar to that on egg oviposition. Mite eggs were more susceptible to sage residuals, and significant reductions in larva emergence rates were observed with both sage dosages after 8 days of treatment. Rosemary and sage extracts showed no insecticidal activity against Ceratitis capitata, although sage oil greatly attracted adult flies (see supplementary file).