Abstract
In order to study weeding efficacy of tadpole shrimps as an agent for biological control of weeds in transplanted rice, their eggs deposited in the soil were released in the plots at the puddling time and the relations between their population and weed growth were surveyed.
The results obtained are as follows:
1) Some metanauplii and youngs of tadpole shrimps (Triops granarius Lucas and T. longicaudatus LeConte) were found on the 4th day after puddling, almost the same time as weed emergence. They began to scratch the soil surface 6 to 7 days after their appearance.
2) The close negative correlation was found between the population density of tadpole shrimps and the amount of residual weeds (r=-0.793).
3) It is indicated that the following regression equation was most suitable to express the relation of the number of residual weeds (y%) to the number of tadpole shrimps per m2 (x); y=1/1.046+1.0518x
4) From this regression curve, the successful population density of tadpole shrimps for control of weeds was estimated at about 50 or more per square meter. They gave no damage to the transplanted rice.
