The weed flora in sugarcane fields of Palghat district.
Eighty fields of sugarcane on red and black soils in Palghat district were surveyed for their weed populations during 1989-90. Of the 48 weed species identified, Ageratum conyzoides was the most widely distributed weed, occurring in 87% of sites surveyed, followed by Tridax procumbens, Eclipta prostrata, Commelina jacobi, Cynodon dactylon and Corchorus capsularis [jute]. Other weeds were more localized. Weed species identified as posing a threat because, although not necessarily widespread, they reached high densities within the crop included Cyperus rotundus, Oldenlandia affinis, Commelina benghalensis, Ageratum conyzoides and Echinochloa colona [E. colonum]. A frequency density index revealed A. conyzoides and C. rotundus to be the most widespread and serious weeds.