Infestation with pathogenic fungi is frequently a cause of poor carrot seed quality. The effect of hydrogen peroxide (H₂O₂) treatment on germination, vigour and health of carrot seeds as well as plant emergence was investigated. Four seed samples were tested. Seeds were soaked in 3, 6, 9 and 12% H₂O₂ solutions for 10, 30 and 60 min. Controls were untreated seeds, seeds treated with fungicide (a.i. 75% thiram), and seeds soaked in distilled water for 10, 30 and 60 min. The fungi from genera Alternaria and Fusarium were frequently detected on tested seeds and dead seedlings. Hydrogen peroxide treatment, regardless of concentration and treatment time, reduced significantly carrot seed infestation with A. alternata, A. radicina and Fusarium spp., however was not effective in the control of A. dauci. Deterioration of seed germination and vigour was observed mostly if seeds were treated with 9 and 12% H₂O₂. Treating seeds with 3% H₂O₂ for 30 min positively affected plant emergence in three of four tested samples, while treatment with 6% H₂O₂ significantly decreased percentage of healthy seedlings in one of these samples and increased it in two of them.

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