Suppression of the soybean cyst nematode, Heterodera glycines, by short-term field cultivation and soil incorporation of mung bean.

Our previous study using pots reported that short-term growth of mung bean (Vigna radiata) may be useful to decrease the density of the soybean cyst nematode (SCN), Heterodera glycines, in soil. The objective of this study was to determine whether short-term growth of mung bean and its incorporation by ploughing decreased SCN density in infested fields. Firstly, we did pot experiments to evaluate the optimum temperature and moisture for hatching in soil. SCN hatching was stimulated at 25 and 30°C and not at 20°C; however, it was stimulated at alternating temperature conditions between 20 and 25°C. Soil moisture levels with pF 2.76 or less were required to stimulate SCN hatch in soil. Field experiments were done in Saitama, Kanagawa and Nara Prefectures, Japan. SCN density was reduced by nearly half even in control plots, in which mung bean was not cultivated and ploughed, in Saitama and Nara Prefectures. However, SCN density was reduced by nearly 80% or more in the three Prefectures, except for one plot in Kanagawa, and the soil temperature and moisture conditions were kept at around 20-30°C and at <pF 2.8. Increase in yield of green soybean by SCN control was estimated at 350 kg (1000 m)−2. Overall, the present study revealed that short-term field cultivation of mung bean and ploughing was a profitable method to decrease SCN density in infested fields and thereby to increase yield of green soybean.