Impact of piper betle leaf extract on grape downy mildew: Effects of combining 4-allylpyrocatechol with eugenol, α-pinene or β-pinene

Abstract

Methanol extract of Piper betle leaves exhibited an inhibitory effect on grape downy mildew. This extract might contain more than two compounds which have different polarities that suppress grape downy mildew. Gas chromatograph-tandem mass spectrometry analysis identified 4-allylpyrocatechol, eugenol, α-pinene, and β-pinene in the methanol extract. Neither of the compounds suppressed grape downy mildew by single treatment. On the other hand, treatment with a combination of 4-allylpyrocatechol with eugenol, α-pinene or β-pinene enhanced the inhibitory effects on grape downy mildew and perfectly suppressed it. The complex extracted from P. betle leaves may be used in organic agriculture as an alternative to chemical fungicides in viticulture.