Influence of selected herbicides on weed infestation and yielding of common valerian (Valeriana officinalis L.)
A field experiment on weed control in valerian canopy was carried out in 2004–2006 in Jaroszewice (central part of Lublin region). Studies involved three herbicide mixtures applied at the stage of 3–4 leaves; herbicides had no certificates to be applied for valerian in Poland. Effects of tested herbicides were compared to traditional (two-stage) chemical weed control. Experiment revealed that the strongest reduction of valerian weed infestation was ensured by mixture of pendimethalin and haloxyfop-R as well as metamitron and propachizafop. Those herbicides were characterized by great selectivity towards valerian. MCPA and chizalofop-P-ethyl caused considerable plant injuries. The yield of valerian showed considerable negative correlation with the degree of canopy weed infestation. Content of valerenic acids in valerian raw material depended mainly on weather course during experiment.