Kava root powder for the control of the economically important nematode, Meloidogyne incognita

The root knot nematode (Meloidogyne incognita) infests numerous commercial crops, causing significant amounts of economic damage. Here, the anti-nematodal potential of commercial powdered root material from kava (Piper methysticum) powder was tested on this species. Pot trials using tomato seedlings were conducted at kava powder concentrations of 1,2 and 5% w/w. The powder was allowed to degrade in the soil for between 0 and 6 weeks before planting and inoculation with juvenile (J2) M. incognita inoculum. Plant health and nematode infestation levels were quantified after 52 days (7.5 weeks). At all concentrations tested, kava powder was found to suppress infection by M. incognita in a dose-respondent fashion, with higher concentrations providing superior nematode control, albeit showing a concomitant reduction in plant health. Concentrations of 1 or 2% kava combined with a degradation time of two weeks prior to planting and inoculation produced the best combination of nematode control while maintaining plant health. There was a significant difference in the inhibition levels produced by Fijian and Vanuatuan kava, likely due to differences in their chemical composition. When used as a soil additive, kava root powder appears to have considerable potential for controlling root knot nematodes.