Test the allelopathic effects of essential oils, such as Cinnamomum zeylanicum, Syzygium aromaticum and Cymbopogon nadrus on weeds, Ambrosia artemisiifolia, Taraxacum officinale and Poa annua and select the volatile oils with the highest impact.
Test and qualify the effect of the most efficient essential oils applied alone or mixed at the same dose rate on Ambrosia artemisiifolia and Poa annua.
Experiments were run in a greenhouse. Treatments disposed in a block fully randomised design with 4 repetitions. Products applied with a greenhouse bench sprayer or with a hand sprayer. Plant canopy injuries were observed by visual estimations, in %, with a scale of 0 to 100% injury. During the last observation plants were cut on their stem base and weighed.
To produce the dose response curves non-linear regression models were applied. Curves were analysed graphically to determine product dose rates to achieve 50 % of leaf injury (ED 50). The presence of synergism or antagonism was estimated with the multiplicative survival model (MSM) and the additive dose model (ADM).
Essential oils based on C. zeylanicum and S. aromaticum produced significant phytotoxic effects already one day after treatment. Over time injury impact decrease. No significant difference in plant weight could be measured 2,3 weeks after treatment.
The effect of the oil mixtures to produce 50% canopy injury (ED 50), on day after treatment, on Ambrosia artemisiifolia at growth stage BBCH 25-29 was qualified as synergism with both models, MSM and ADM. The effect of the oil mixtures on P. annua at growth stage BBCH 23-24, on day after treatment, was qualified as antagonism with ADM. Phytotoxic effects produced by C. zeylanicum leaf were lower and more variable than the impact of other products. 50% of canopy injury was already achieved with 2 to 3% v/v essential oil dose rates.
Location: Harper Adams University College, Newport, UK.