Efficiency of citronella grass (Cymbopogon winterianus Jowitt) extracts to control Zoothamnium sp. in black tiger shrimp (PL15 stage)

Study on the efficiency of Citronella grass (Cymbopogon winterianus Jowitt) extracts to control Zoothamnium sp. was conducted in the laboratory at Kasetsart University. Comparison between two methods of extractor, water distillation an soxhlet extractor, revealed that sohlet extractor was about 225 times more efficient than the water distillation, based on the concentration that could give 100 percent mortality of Zoothamnium sp. in 24 hours (0.008 g/l from soxhlet extractor and 1.8 g/l from water distillation). The LC sub(50) of PL15 shrimp in 24 hours of this extract from water distillation was 21.05 g/l while from soxhlet extractor was 1.88 g/l. Those concentrations, 0.008 g/l from soxhlet extractor and 1.8 g/l from water distillation did not harmful to the PL15 shrimp measured by dissolved oxygen and pH of water.