Effect of rate of drying of soil on the survival, infectivity and development of the root-knot nematode, Meloidogyne incognita

The mortality, loss of infectivity and slowing of development of the root-knot nematode, Meloidogyne incognita, were positively correlated to the rate of moisture loss from soil. The rate of drying was regulated by two techniques viz. air-drying of soil layers of 3–9 cm thickness in shade at room temperature; or by keeping the soil at relative humidity varying from 60 to 100 per cent in the surrounding air, both for a period up to 45 days. With increase in moisture tension to 25.5–51.5 bars in 9–3 cm thick layers there was 62–85 per cent mortality of M. incognita (J-2) during 45 days as apainst only 54 per cent mortality in sealed soil with 2.94 bars suction. In the soil stored at 100-60 per cent RH the juvenile mortality during 45 days increased from 75 to 92 per cent with the moisture tension increasing from 0.01 to 17.6 bars. The infectivity of surviving M. incognita J-2 on green gram, Vigna radiata cv. Pusa-105 root decreased from 48 per cent of fresh population to 38, 35, 36 and 33 per cent in sealed, 9, 6 and 3 cm thick soil layers, respectively. There was a delay of 2–4 days in the onset of oviposition in case of population surviving in 3 cm soil layers after 45 days. These findings reveal that inducing faster drying of field soil may help in significantly reducing the population densities of nematodes and the damage to the subsequently grown crop.