Department of Agronomy, Faculty of Agriculture Annamalai University, Annamalainagar-608 002 (T. N.), India.
Imazapyr at 0.5 kg ha−1 resulted in maximum reduction in fresh weight of water hyacinth with 100% control. Paraquat, 2,4-D and glyphosate reduced the growth of water hyacinth. Water quality in relation to dissolved oxygen and pH was affected by all treatments. Paraquat at 0.9 kg ha−1, 2,4-D at 1.0 kg ha−1 and glyphosate 2.2 kg ha−1 resulted in reduced dissolved oxygen content compared to the untreated control where commoon carps were cultured without any water hyacinth or herbicide treatments. However, the dissolved oxygen content in imazapyr treated water was reduced to 0.35 ppm. Presence of water hyacinth alone also reduced dissolved oxygen content to 2.59 ppm. All herbicidal treatments lowered,the water pH and resulted in higher mortality of common carp. Imazapyr treatment had the highest common carp mortality (71.4%). In contrast, glyphosate treated water hyacinth resulted in only 14.3% mortality of common carp.
