Abstract
Experiments were carried out to analyse the performance, damage to rice seedlings and the weeding effect of the apple snail (Pomacea canaliculata Lamarck), under different methods of water management in paddy fields infested with the snail for several years at depths of 5-6cm from the field surface.
1. The shell height of almost all the snails ranged from 0.8 to 2.7cm in the paddy fields several days after rice transplanting.
Densities of the snail varied from 3 to 7 per m2. The snails were distributed uniformly in the paddy fields under a water level of 1-2cm or more in depth.
2. Damage caused by the snails to rice seedlings was negligible when mature seedlings were transplanted and then kept under shallow flooding management for 10 days. When young seedlings were kept under shallow flooding management for 15 days after transplanting, they sustained considerable damage with partial loss of stand in the field under the low water level. However the damage to the seedlings did not result in severe yield reduction due to compensatory effects.
3. Weeding activity of the snails was effective even though standard water management was resumed after surface drainage was applied for 15 days after transplanting.
