The invention relates to plant extracts, especially based on species of the genus Agapanthus and combinations thereof with other extracts deriving from other plants. The invention further relates to the isolation, purification and identification of compounds in these extracts. The plant extracts and the isolated substances show significant antimicrobial activity, especially antifungal activity, and bio-stimulatory efficacy, when applied to other plants in vitro and in vivo, including under field conditions. The products according to this invention are suitable to be used as plant protecting agents for many crops and economic plants as an alternative for chemical pesticides.