New knowledge for yield, composition and insecticidal activity of essential oils obtained from the aerial parts or seeds of fennel (Foeniculum vulgare Mill.)

• Essential oils obtained from fennel as active ingredient of botanical insecticides.
• The tested genotype Foeniculum vulgare cv. Moravsky provided a high biomass yield.
• Two harvests per year; the yield of fresh above-ground biomass was higher compared to EOs obtained from seeds.

Fennel is an important medicinal and aromatic plant. Essential oils obtained from this plant have found application in various fields, including the production of botanical insecticides. In two seasons, we evaluated the yields of seeds and above-ground biomass, and we monitored the yield rate, chemical composition and insecticidal efficacy of the EOs.We found out that the tested genotype provided a high biomass yield, with two harvests per year; the yield of fresh above-ground biomass was 15.8 kg/m2 in the first year, and 14.3 kg/m2 in the second year, or 3.3 kg/m2 and 3.1 kg/m2, respectively, of dry biomass. This biomass could be used to potentially obtain 366.2 kg and 317.4 kg of EO/ha, respectively, in the first and second year, i.e. an amount statistically significantly higher compared to EOs obtained from seeds (215.3 kg and 187.9 kg of EO/ha, respectively, for the first and second year).Their analysis detected 7–9 substances (relative contents >0.05%), forming 88.99–98.59% of the EO contents. All EOs contained a majority share of trans-anethole (48.42–63.23%). The highest amount of trans-anethole was found in EOs obtained from seeds (≥60%).All EOs obtained from different biomasses exhibited important insecticidal effects against Culex quinquefasciatus larvae, Spodoptera littoralis larvae and Musca domestica adults.Czech fennel F. vulgare cv. Moravsky is a high-growth genotype that provides a high yield of above-ground biomass; this biomass can be used with a benefit to obtain EOs utilizable for the development and production of botanical insecticides