The effect of acetic acid, grapefruit extract and selected essential oils on germination, vigour and health of carrot (Daucus carota L.) seeds

Seed infection with Alternaria spp. is an important source of severe carrot diseases. The aim of the study was to evaluate the effects of carrot seed treatments with acetic acid, grapefruit extract and volatile compounds of fir (Abies alba Mill.) and thyme (Thymus vulgaris L.) essential oils on their germination, vigour and health. Seeds of two samples were soaked for 30 min in 0.5, 1 and 2% acetic acid, 0.5 and 1% Biosept Active (33% of grapefruit extract), or treated for 72 h or 96 h with volatile compounds of fir and thyme oils individually (10 µl), and jointly (5+5 µl). Controls were untreated seeds and seeds soaked in distilled water. Acetic acid effectively controlled A. alternata and A. radicina in both samples, and did not affect adversely seed germination, however, at the highest concentration deteriorated seed vigour. Biosept Active was less effective, however at 1% concentration decreased seeds infestation with A. alternata in sample I, and at concentrations of 0.5 and 1% reduced percentages of seeds infested with A. alternata and A. radicina in sample II. Essential oils treatments in some cases favoured growth of A. dauci and A. radicina.