Abstract

Three greenhouse experiments were established in order to evaluate the protective effect of naphtalic anhydride (0,5 and 0,75%), flurazole (0,1 and 0,2%) and oxabetrinil (0,1 and 0,2%) used as seed treatments in rice cv Milagro Filipino (MF), as compare with non-selective herbicides atrazine (1,8 kg/ha), atrazine/metolachlor (0,78/0,75 kg/ha), acetochlor (2,1 kg/ha), alachlor (2,5 kg/ha) and metolachlor (1,92 kg/ha). The effect of alachlor with four red rice biotypes and MF treated with naphtalic anhydride was also evaluated. Neither flurazole nor oxabetrinil protected rice from any one of the herbicides, but naphtalic anhydride (0,75%) protected rice from alachlor (2,5 kg/ha). Alachlor (2 kg/ha) temporarily reduced rice seedling height, but there was no difference in height between treated and non-treated plants at 25 days after application (DAA). Dry weight of the MF check plants was statistically similar to those obtained from plants originated from seed treated with naphtalic anhydride (0,75%) and applied with alachlor at 1, 1,5 and 2 kg/ha. At 7 DAA, control of the different red rice biotypes with alachlor varied from 40 to 80% with 1 kg/ha, from 80 to 98% with 1,5 kg/ha and from 98 to 99% with 2 kg/ha. Moreover, at 25 DAA, controls varied from 30 to 62% with 1 kg/ha, from 43 to 83% with 1,5 kg/ha and from 58 to 96% with 2 kg/ha.