Diatomaceous earth as physical control agent for root-knot nematode.

This study evaluated diatomaceous earth (DE), a naturally occurring mineral composed primarily of amorphous silicon dioxide (SiO₂), as a physical control agent against the root-knot nematode Meloidogyne javanica infecting eggplant (Solanum melongena). Under laboratory conditions, DE was tested against second-stage juveniles (J2) at different concentrations. Among the concentrations of 0.01, 0.05, 0.1, 0.3, 0.5, 1.0, and 2.0 g/L, mortality rates of 100% were observed at concentrations ranging from 0.05 to 2.0 g/L, while 85% mortality was recorded at the lowest concentration (0.01 g/L). In greenhouse conditions, DE was applied at concentrations of 0.05, 0.5, 1.0, and 2.0 g/L using three application methods: root dipping and foliar spray at inoculation time, and soil drench at three distinct time points relative to nematode inoculation. All treatments significantly (P ≤ 0.05) reduced nematode infection parameters in a concentration-dependent manner. Root dipping at 2.0 g/L resulted in reductions of 92% (galls), 93% (egg masses), and 92% (adult females). Soil drench applied at the time of inoculation produced reductions of 86%, 85%, and 85% for the same parameters, respectively; while foliar spray resulted in reductions of 73%, 68%, and 73%. Among the application methods, soil drench consistently produced the greatest suppression of J2 populations. In addition to nematode control, DE application was associated with increased plant growth parameters. Soil drench applied one week after inoculation increased root dry weight by 178% at 0.5 g/L and by 185% at 2.0 g/L. These results indicate that DE has potential as a physical control agent against M. javanica infecting eggplant and may warrant further investigation for integration into nematode management strategies.