A condensed heterocyclic derivative represented by general formula (I) and a weedkiller, wherein R represents hydroxy, R³ and R⁴ represent each alkoxy, W represents oxygen, Yn represents hydrogen, Z represents methine, and A represents a 5- or 6-membered heterocyclic group which may be substituted. The derivative does not injure crops in the water treatment in a paddy field, upland farming, soil treatment and foliage treatment, and has an excellent weedkilling activity against gramineous and nongramineous weeds.
A condensed heterocyclic derivative of the formula (I): ##STR1## (wherein R is a hydroxyl group, R.sup.3 or R.sup.4 is an alkoxy group, W is an oxygen atom, Yn is a hydrogen atom, Z is a methine group, and A is a 5- or 6-membered heterocyclic ring which may be substituted, and a herbicide, are presented. When used for paddy field treatment, upland soil treatment and foliage treatment, the condensed heterocyclic derivative of the present invention exhibits excellent herbicidal activities against gramineous and non-gramineous weeds without adversely affecting crop plants.