Sammendrag
The effect of up to 19 essential oils (EOs) isolated from different types of plant species against potato late blight, Phytophthora infestans has been studied in vitro and under greenhouse conditions. Two isolates of P. infestans were in a first screening exposed to an inhibition test using the EOs in a standard plate assay measuring the diameter of the development fungal zone. Representative oils selected from this first screening were then applied to susceptible potato plants and both the fungicidal and phytotoxic effects were examined. While most of the EOs tested in the fungus plate assay showed no desirable inhibitory action against the pathogen, four of the EOs produced an inhibition zone of 80%. EOs from thyme had e.g. an 89% inhibitory effect on the fungus isolates, but did not display protection in the potato study, and in addition caused phytotoxic symptoms. On the other hand, treatment with hyssop in the plate assay demonstrated only up to 45% of inhibition, but hyssop promoted good fungus protection for the plants and stimulated the plant growth without any signs of phytotoxity.
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