Mechanical and chemical control of red rice (Oryza sativa L. var. sylvatica) in rice (Oryza sativa L.) pre-planting

The effectiveness of different herbicides and mechanical methods for the pre-planting control of red rice seedlings in a rice cv. Loto crop were assessed in field experiments in North-west Italy. In 1995-1996, dalapon-sodium [dalapon] (12.75 kg a.i. ha-1) was compared to mechanical control using a blade harrow and light mouldboard plough, both working at 8-10 cm depth. The weed control obtained with mechanical treatments ranged between 69 and 91%, while with dalapon it was always >92%. Harrowing and shallow ploughing gave similar or lower rice yields to those obtained with dalapon (6.2-6.4 t/ha). Ploughing reduced the red rice seed bank by 14% after 2 years, harrowing caused a slight reduction, but dalapon increased the seed bank by approximately 1. 6-fold. The effective working time of dalapon was between 12-20% of that achieved with harrowing and shallow ploughing. In 1995-1997, quizalofop-ethyl isomer D, cycloxydim, dalapon, glyphosate-trimesium salt, glyphosate-isopropylammonium salt, haloxyfop-ethoxyethyl, clethodim, dimethenamid + dalapon, clethodim + mineral oil and oxadiazon + glyphosate-isopropylammonium salt were compared. The best red rice control was obtained with cycloxydim, clethodim and dalapon, providing >95% control.