Nematicidal Potential of Clove Extract Compared to Oxamyl Against Meloidogyne Incognita in Vitro and in Vivo

Abstract

Chemical nematicides are commonly used to control plant-parasitic nematodes, specifically Meloidogyne spp., but they have negative impacts on human health and the ecosystem. In response, nematologists are turning to botanicals for nematode control. In this study, fresh and uniform-sized egg-masses or 100 infective juveniles (J2s) of Meloidogyne incognita were exposed to ethanolic bud clove (Syzygium aromaticum) extract and the nematicide oxamyl in vitro. It was found that, the type of agents tested (clove and oxamyl), concentrations (250, 500, and 1000 µg/ml for clove extract and 0.6, 1.2, and 2.4 µg/ml for oxamyl), and exposure times (one, four, and seven days) were key factors affecting the number of emerged and dead juveniles. The concentrations of oxamyl were based on half the recommended rate (HRR), the recommended rate (RR), and double the recommended rate (DRR). Both clove and oxamyl significantly inhibited egg hatching and increased juvenile mortality of M. incognita compared to distilled water treatment. Oxamyl showed a relatively higher effect. At the highest concentrations of clove and oxamyl, the percentage of hatching inhibition after 1, 4, and 7 days was 87.89% (85.31 %), 72.47 % (82.70 %), and 61.73% (67.63 %), respectively. The corresponding values for juvenile mortality were 36.5 % (53.3 %), 52.4 % (70.9 %), and 62.2 % (99.0 %), indicating the effectiveness of both treatments in controlling M. incognita. In a greenhouse study, the effects of clove extract and oxamyl on M. incognita-infected cucumber plants were investigated. Both treatments were applied at the same concentrations as in the in vitro assay. Results showed that both clove extract and oxamyl significantly reduced nematode galling and reproduction compared to the control group, with oxamyl having the most pronounced effect. The control group exhibited the highest levels of galling and reproduction. Higher concentrations of both treatments demonstrated increased efficacy. The percentage reduction in galling and reproduction for clove extract at the three concentrations was 35.4% (87.52%), 41.47% (89.82%), and 47.54% (91.97%), respectively. For oxamyl treatments, the corresponding values were 77.31% (97.46%), 81.21% (97.93%), and 96.96% (99.74%), respectively. Furthermore, both clove extract and oxamyl treatments significantly improved the growth of cucumber plants, as evidenced by increased shoot length and fresh weight.