Fungicidal activity of Ranunculus asiaticus and other weeds against Fusarium oxysporum f.sp. lycopersici

The effects of aqueous extracts of some common weed species against Fusarium oxysporum Schlecht f.sp. lycopersici (the causal agent of tomato wilt disease) were investigated under laboratory conditions. Anagallis foemina L., Cerastium dicotomum L., Falcaria vulgaris L., Ranunculus asiaticus L., Scorpiurus mur-icatus L. and Solanum nigrum L. extracts were the most toxic to the fungus. Further studies on buttercup (Ranunculus asiaticus L.) showed that fresh shoot extract of this species prevented growth of F. oxysporum when incorporated into agar medium. Extracts of different parts of the plant inhibited fungus growth and sporulation, but the fungitoxicity decreased with incubation period with only slight changes in the toxicity of fresh shoot extract. The shoot and fresh parts extracts were more toxic than root and dried tissue extracts. Addition of 0.5 ml fresh shoot or 1 ml fresh root extract to the growing medium significantly reduced fungal colony growth, and the effect was extract concentration dependent. Fresh shoot extract of R. asiaticus added to a liquid medium significantly reduced mycelial dry weight compared with the control, and incorporation of 0.1 g dried shoot or 0.2 g dried roots in the media strongly inhibited fungus growth. Results of a pot experiment showed no harmful effects of R. asiaticus extracts on tomato growth.