Ferulago campestris Essential Oil as Active Ingredient in Chitosan Seed-Coating: Chemical Analyses, Allelopathic Effects, and Protective Activity against the Common Bean Pest Acanthoscelides obtectus

Ferulago campestris is an aromatic plant, distributed in Mediterranean Europe, and a source of essential oils (EOs) regarded as promising alternatives to synthetic herbicides and pesticides. F. campestris EO, hydrodistilled and analyzed, was tested for its antigerminative activity and for its effect on radicle elongation, hydrogen peroxide concentration, and lipid peroxidation on four infesting weed species (Papaver rhoeas, Taraxacum campylodes, Poa annua, and Setaria verticillata) and on Phaseolus vulgaris. Its repellent ability was also tested against Acanthoscelides obtectus, a pest commonly affecting P. vulgaris during storage. Moreover, a chitosan coating layer was developed with the addition of F. campestris EO and tested for its toxic and oviposition-deterring effects against A. obtectus. Myrcene, α-pinene, and γ-terpinene were detected as the main compounds in F. campestris EO. The EO demonstrated a selective in vitro antigerminative activity towards the weed species, without affecting the bean seeds. Moreover, the chitosan coating layer exerted a dose-dependent repellent effect against A. obtectus adults, thus effectively protecting the bean seeds, while preserving their germinative ability. To the best of our knowledge, this is the first report on a chitosan–EO coating proposed with the aim of protecting bean seeds for sowing from insect attack.

Setaria verticillata (bristly foxtail).

S. verticillata is listed by Holm et al. (1979) as a 'serious' or 'principal' weed in 11 countries in Europe, Asia, Africa, South America and the Pacific. From its origins in Europe and perhaps Africa, it has been accidentally introduced to many other countries across the world. It is often listed as one of the two or three most important weeds in a wide range of crops, within and outside its native range, and it can also become dominant in grassland. The combination of ready dispersal by its 'sticky' seed and seed-heads, and its C4 physiology and rapid growth make it an extremely successful invader. It adapts to local conditions rapidly and has developed resistance to atrazine and other herbicides.

Herbicidal Activity of Thymbra capitata (L.) Cav. Essential Oil

The bioherbicidal potential of Thymbra capitata (L.) Cav. essential oil (EO) and its main compound carvacrol was investigated. In in vitro assays, the EO blocked the germination and seedling growth of Erigeron canadensis L., Sonchus oleraceus (L.) L., and Chenopodium album L. at 0.125 µL/mL, of Setaria verticillata (L.) P.Beauv., Avena fatua L., and Solanum nigrum L. at 0.5 µL/mL, of Amaranthus retroflexus L. at 1 µL/mL and of Portulaca oleracea L., and Echinochloa crus-galli (L.) P.Beauv. at 2 µL/mL. Under greenhouse conditions, T. capitata EO was tested towards the emergent weeds from a soil seedbank in pre and post emergence, showing strong herbicidal potential in both assays at 4 µL/mL. In addition, T. capitata EO, applied by spraying, was tested against P. oleracea, A. fatua and E. crus-galli. The species showed different sensibility to the EO, being E. crus-galli the most resistant. Experiments were performed against A. fatua testing T. capitata EO and carvacrol applied by spraying or by irrigation. It was verified that the EO was more active at the same doses in monocotyledons applied by irrigation and in dicotyledons applied by spraying. Carvacrol effects on Arabidopsis root morphology were also studied.

Herbicidal potential of lavender (Lavandula angustifolia Mill.) essential oil components on bristly foxtail (Setaria verticillata (L.) P. Beauv.): Comparison with carvacrol, carvone, thymol and eugenol

Essential oils are a plentiful source of plant compounds for potential use in the development of natural herbicides. With this in mind, the phytotoxicity of ten major essential oil components of lavender (Lavandula angustifolia Mill.) on the weed species bristly foxtail (Setaria verticillata (L.) P. Beauv.) was determined using a perlite-based Petri-dish bioassay. Their phytotoxicity was also compared with that of well-known phytotoxic essential oil components (carvacrol, thymol, carvone and eugenol) of oregano (Origanum vulgare L.) and clove (Syzygium aromaticum (L.) Merr. & L.M. Perry) essential oils. Potential synergistic or antagonistic effects between carvacrol or eugenol with other components of lavender essential oil were investigated. Regarding the most phytotoxic components, terpinen-4-ol at 80 nL/cm3 completely inhibited the germination and root length of bristly foxtail, displaying similar phytotoxicity to carvone and thymol. Like carvacrol, lavandulol and linalyl acetate caused total (100%) germination and root length reduction of bristly foxtail at 160 nL/cm3, while the same effect was achieved by lavandulyl acetate at 320 nL/cm3. A synergistic effect was also observed when carvacrol or eugenol were combined with ocimene, 3-octanone, ?-terpineol or terpinen-4-ol. Focusing on the development of alternative weed control strategies, lavender essential oils containing high concentrations of terpinen-4-ol, lavandulol or linalyl acetate could be useful for the production of natural herbicides. These essential oil components combined with selected oregano or clove essential oil components, increase phytotoxicity and weed control due to the synergistic effect observed when in mixture.

Evaluation of Local Weed Flora of South Gujarat for Dry Flower Products

An investigation was carried out to explore and evaluate the weed flora to obtain dried ornamentals for making of dry flower products. Nine species of weeds viz., Dinebra arabica, Argyreia speciosa, Setaria verticillata, Dactyloctenium aegyptium, Cyperus rotundus, Celosia argentea, Digitaria sanguinalis, Echinochloa colonum and Eragrostis pilosa growing locally in the south Gujarat region were evaluated for the study. Either inflorescence or leaves of the weeds employing press drying method were evaluated for their dried ornamental value in the year 2015-2017. Among different weeds, maximum percent loss in weight after drying was observed in the leaves of Argyreia speciosa followed by the inflorescence of Echinochloa colonum after drying. No shattering was observed in the dried leaves of Argyreia speciosa and dried inflorescence of Celosia argentea and Cyperus rotundus while maximum shattering in the inflorescence was observed in the dried inflorescence of Echinochloa colonum. Maximum time taken for drying (5.87-6.1 days) was required in Argyreia speciosa (leaves) followed by inflorescence of Celosia argentea (4.3- 4.41 days) and Setaria verticillata (4.3-4.37 days) in both the years and pooled data. Maximum shelf life after drying (more than 170 days) was observed in the dried leaves of Argyreia speciosa which was at par with dried inflorescence of Celosia argentea. Ornamental value was found to be the best in the dried leaves of Argyreia speciosa and dried inflorescence of Celosia argentea and Setaria verticillata with highest visual score of (5), followed by Echinochloa colonum and Eragrostis pilosa with 4 as visual score as observed in both the years.