Velocity of Meloidogyne ethiopica second-stage juveniles in sandy soil under several soil moisture conditions

Calculating the velocity and migration of plant-parasitic nematodes in soil is important for understanding individual roles in nematode populations. Tracking individual nematodes in the soil is difficult, and any marking system can alter the behavior of second-stage juvenile (J2) nematodes. This study examined the velocity of Meloidogyne ethiopica J2s under different soil moisture conditions and proposed a maximum migration distance. Evaluations considered 16 velocity categories (distances of 1.5, 4.5, 9.5, and 14.5 cm; experimental periods of 3, 6, 16, and 26 d) and four moisture ranges (40–55, 55–70, 70–85, and 85–100%) in pots with sandy soil under controlled temperature and moisture conditions. The weighted average velocity of J2 specimens that reached the roots was 70–75 μm h⁻¹, and the maximum recorded velocity was 378 μm h⁻¹. The fastest average velocities were 100 μm h⁻¹ (Test 1) and 89 μm h⁻¹ (Test 2). The average velocity at 85–100% soil moisture was very similar to the overall weighted average velocity of M. ethiopica J2s because most movement of the J2 specimens occurred at higher soil moisture ranges. Few J2s moved in the 40–55% soil moisture range. At slow velocities (24, 39, and 72 μm h⁻¹), the number of J2s reaching the roots was highly correlated with higher soil moisture. The majority of M. ethiopica J2s did not move or moved at velocities slower than 24 μm h⁻¹, implying that unless the plant roots were near the nematode, they will not be infested.