Efficacy of new herbicide molecules for weed management in wet direct seeded rice

Weeds are one of the major biotic constraints limiting crop production in direct seeded rice and use of effective herbicides improve grain yield besides overcoming labour problem. The field investigation carried out during wet seasons of 2010 and 2011 at Andhra Pradesh Rice Research Institution and Regional Agricultural Research Station, Maruteru on chemical weed management using new molecules in wet direct seeded rice revealed that post emergence application of penoxulam @ 25.0 g ai/ha at 15–20 days after sowing (DAS) controlled the weeds more effectively as that of weed free throughout crop growth period or hand weeding twice at 20 and 40 DAS and recorded lower weed density, weed bio mass, higher weed control efficiency (76.9%), higher number of productive tillers (285 m2) with more panicle weight (5.48 g) and ultimately resulted in higher grain yield (5603 kg/ha) accounting for 28.1% increase over unweedy check and also recorded lowest weed index (0.49). Reduction in grain yield to an extent of 21.9% was observed due to weeds in direct seeded rice in deltaic soils of coastal region during wet season.