Abstract
Experiment on chemical and cultural control of the rice cyst nematode was conducted in a field which had indicated typical soil-sickness due to successive cropping of upland rice. Preplant treatment with D-D mixture at 30 l/10 ares was most effective and increased a yield of paddy rice variety by about 30%. This effect was not obvious in the next season, resulting from a rapid build-up of the cyst population at harvest time in the first year. Similar treatment with EDB (30%) was not as effective as D-D, and a higher cyst population was recovered. Treatment with Lannate (methomyl) 5 % granules at sowing time at a rate of 30 kg/10 ares was severely phytotoxic in combination with DCPA herbicide application which was made about one month after sowing. Another experiment indicated that cropping of soybeans or sweet potatoes decreased the cyst population remarkably at the end of the first season, but even 3-years successive cultivation of these non-hosts failed to decrease the population to zero. Rice yields of plots where a 3-year successive cultivation of soybeans or sweet potatoes had been made, was as good as 3.7 or 2.8 times that of the plots where rice had been successively cultivated for at least more than four years. Hatching stimulation of a water extract of rice roots to eggs of the cyst nematodes was apparent at 25°C under laboratory condition. Similar stimulation of kidney beans or sweet potato roots to this nematode was less and inhibitive at some concentration.
