The plant strengthening effect of Artemisia absinthium extract, Tanacetum vulgare extract and the plant strengthening product “Pflanzen Vital Spray S” (containing both A. absinthium and T. vulgare extracts), against Thrips tabaci (Thysanoptera: Thripidae) on cucumber (Cucumis sativus, var. Korinda) was evaluated using leaf disc bioassays and histological characterisation of cucumber-leaf sections. To exclude a direct toxic effect on the pest, the direct contact toxicity of the products was tested on 2nd instars of T. tabaci. No significant increase in the 24 and 48 h mortality rate could be observed compared to water or zero treatments. Feeding and ovipositional rate were evaluated using a no choice leaf disc bioassay. No significant differences could be detected between product and water treated plants. Choice leaf disc bioassays were conducted to check for settling and ovipositional preference of T. tabaci. Leaves of A. absinthium and “Pflanzen Vital Spray S” treated plants were less preferred then water treated leaves but no influence on the ovipositional preference could be detected. Leaves from T. vulgare treated plants did not result in significant differences in the settling preference but thrips preferred to lay eggs on T. vulgare treated leaves over water treated ones. For the histological characterisation thin leaf sections were produced using Vibratome and Microtome. Vibratome sectioned leaves were checked for differences in the epidermis thickness. A. absinthium and T. vulgare treated plants had thicker epidermis cells then water treated plants. Leaf cross sections produced by means of Microtome were checked for differences in the thickness of upper epidermis cell walls. All three treatments had thicker cell walls then the water treated control leaves. Additional staining of callose and lignin exhibited no differences between the treatments. Staining of pectin resulted in a higher coloration within the product treated leaves compared to the water treated ones.