Assessing the potential of kava (Piper methysticum Forst) and wild kava (Piper aduncum L.) as organic amendments for managing root-knot nematodes

Kava (Piper methysticum Forst) and wild kava (Piper aduncum L.) were evaluated for their efficacy against root-knot nematodes. Plant materials were tested as soil additive in pot trials at 2% and 4% concentrations for 0, 1 and 2 week degradation periods. Effects on the root-knot nematode, M. incognita, and its host, tomato, were recorded. All the tested materials reduced the number of galls compared to the control. Generally, maximum gall suppression was achieved at higher concentration (4%) and with no degradation time. Gall suppression was directly related to concentrations of plant materials, but not with the degradation time after soil incorporation. Kava powder, kava peelings and kava kosa caused maximum gall suppression but were phytotoxic. Kava stem, kava leaf and wild kava leaf, on the other hand, resulted in lower gall suppression but enhanced plant growth. These plant species are good candidates for further trials as soil amendments.