Evaluation of butachlor for control of some submerged macrophytes along with its impact on biotic components of freshwater system

ABSTRACT

In this investigation, the efficacy of the herbicide butachlor, [N-butoxymethyl-2 chloro-2[1], 6[1] diethyl 1 acetanilide] was tested against few common submerged macrophytes namely Hydrilla [Hydrilla verticillata [L.] Royale], Najas [Najas minor All.], Nechamandra [Nechamandra alternifolia [Roxb.] Thwaites] and Ottelia [Ottelia alismoides [L.] Pers.] of freshwater fish ponds. Almost complete decay of Hydrilla, Nechamandra and Ottelia was achieved at 7.5 L of active ingredient/ha/m butachlor within 15 days while the herbicide showed no negative effect on Najas. However at the same concentration of butachlor, total mortality of zooplankton and water fern Azolla [Azolla caroliniana Lamarck] occurred within seven days. In case of few freshwater fish species like Rohu [Labeo rohita], Channa [Channa punctatus], Anabas [Anabas testitudineus] and Heteropneustes [Heteropneustes fossilis], total mortality occurred upto 90 days after application of the same dose of butachlor but fish survived beyond 120 days of herbicide application indicating degradation of the herbicides