Nematicidal and ovicidal activities of Dryobalanops aromatica and Mentha haplocalyx var. piperascens-derived materials and their formulations against Meloidogyne incognita second-stage juveniles and eggs

Nematicidal and hatching inhibition activities (HIA) of the methanol extracts from Dryobalanops aromatica (DA) and Mentha haplocalyx var. piperascens (MH), their constituents, and emulsified concentrate and granule formulations containing the methanol extracts as active ingredients, were compared with those of commercial nematicides, cadusafos and fosthiazate, against Meloidogyne incognita second-stage juveniles (J2) and eggs using well plate, container and pot assays. In a well plate assay with J2, DA applied at 500, 250 and 125 ppm resulted in 100, 95 and 55% mortality, respectively, while MH showed 80% mortality even at the lower concentration of 63 ppm. MH gave stronger HIA than DA at 1000 and 500 ppm. In addition, α-pinene, camphor, borneol and p-menthole, which are the main components of DA and MH extracts, showed strong nematicidal properties and HIA. In particular, the nematicidal activity of p-menthole among them was the highest and its HIA was also stronger than that of cadusafos and fosthiazate. In a container test using emulsifiable concentrate (EC) and granule (G) formulations containing 50 and 30% DA and MH, respectively, EC of D. aromatica showed a stronger LC50 value (0.203 μl (g soil)−1) than G formulation (0.935 mg (g soil)−1). However, their effects were fewer than MH formulations. The lethality of EC and G formulations containing MH was comparable to that of fosthiazate soluble concentrate and granule formulations. In another test using pots containing soils naturally infected by M. incognita, these plant formulations significantly inhibited the nematode-population density judging from the number of galls that formed on tested tomato roots after 8 weeks. These results suggest that DA and MH methanol extracts, as well as their constituents, might be useful as management agents against M. incognita.