Effects of Temperature, Humidity and Different Rice Growth Stages on Vertical Migration of Aphelenchoides besseyi

The vertical migration of Aphelenchoides besseyi under different temperatures and humidities and at different rice growth stages was investigated. It was found that the optimum temperature for the development and reproduction of A. besseyi was 25-30°C. At the same temperature, the rate of vertical migration increased with rising relative humidity. Artificial inoculation tests showed that at the elongation stage, nematodes survived mainly on the upper and middle parts of rice culms, and the number of nematodes decreased by 50% at 20 days after inoculation compared with that at 5 days after inoculation. Whereas at the booting stage, nematodes accumulated in young panicles and reproduced quickly, and the average number of nematodes at 20 days after inoculation increased to 164.5, three times of that at 5 days after inoculation.