Field experiments were conducted to test the efficacy of pyrithiobac on the control of carpet weed (Trianthema portulacastrum L.) in cotton during the kharif seasons of 1996 and 1997 at Hisar. Pyrithiobac application alone at 100 g ha−1 applied as pre-emergence or post-emergence application of pyrithiobac+surfactant (75 g ha−1+0.25%) treatments proved highly effective against carpet weed. Pyrithiobac was not effective against barnyard grass. Preemergence application of pendimethalin at 1500 g ha−1 resulted in good control of barnyard grass and significantly gave higher seed cotton yield than weedy check but was at par with pyrithiobac treatments. Maximum seed cotton yield was recorded under season-long weed free situations.
