Herbicidal Potential of Essential Oils from Three Mediterranean Trees on Different Weeds

The essential oil composition of Juniperus phoniceae, Pistacia vera and Pistacia terebinthus was analyzed by GC and GC–MS analysis and their bioherbicidal activity was evaluated against four weeds species, Sinapis arvensis, Trifolium campestre (dicots), Lolium rigidium and Phalaris canariensis (monocots). Qualitative and quantitative differences between oils were observed. All oils were rich in monoterpene hydrocarbons, the major constituents of J. phoniceae were α-pinene (49%) and α-terpinene (8%) and the major components in P. vera and P. terebinthus were α-pinene (16-19%), α- terpinene (32-41%) and limonene (4-25%). Tested oils strongly inhibited the germination and seedling growth of all weeds, in a dose dependent manner with dicots weeds being significantly more sensitive than monocots, indeed, at the dose of 4µl/ml, germination of S. arvensis and T. campestre was totally inhibited, while for the same dose, germination and seedling growth of L. rigidium and P. canariensis were partially reduced. Essential oils increased the level of proline and caused a severe electrolyte leakage from the roots of all tested weeds indicating membrane disruption and loss of integrity. Our results show that essential oils of forestry trees have an important phytotoxic effect on seed germination and seedling growth of weeds. The phytotoxic activity of the essential oils may be attributed to their relatively high content of monoterpene hydrocarbons. It can be suggested that these essential oils have the potential to be used as a bioherbicide.