Abstract
Lolium rigidum Gaud. is one of the most common weed species in winter cereals in Northeastern Spain. Herbicide resistance has been growing since the mid 90's and exclusive herbicide use is not enough in many cases, so that it is necessary to combine as many control tools as possible. Six field trials have been conducted during the cropping seasons 2001-02, 2002-03 and 2003-04 on winter cereal infested with herbicide resistant L. rigidum in Northeastern Spain testing different cultural control strategies. Sowing delay was conducted at five fields, mouldboard ploughing at four fields, the combination of sowing delay and ploughing at two fields, increasing the cereal sowing density and combined with sowing delay at one field. Sowing delay was confirmed to have an irregular efficacy depending on the L. rigidum emergence during the delay period. In the trials, weed emergence was reduced up to 88% in the best case but there was no effect in two cases. Ploughing had a more constant efficacy and reduced weed emergence between 50 and 80% although stoniness impeded in one occasion a correct soil inversion causing a very low efficacy. Increasing the cereal sowing rate did not reduce the weed population. The combination of the different methods did not increase significantly the individual efficacy, and one method was clearly more effective than the other, depending on the trial. In fields with high L. rigidum density, these methods are not effective enough and need to be combined with other methods, which are discussed in the text.
Highlights
Lolium rigidum Gaud. is one of the most common weed species in winter cereals in Northeastern Spain
Six field trials have been conducted during the cropping seasons 200102, 2002-03 and 2003-04 on winter cereal infested with herbicide resistant L. rigidum in Northeastern Spain testing different cultural control strategies
Sowing delay was conducted at five fields, mouldboard ploughing at four fields, the combination of sowing delay and ploughing at two fields, increasing the cereal sowing density and combined with sowing delay at one field
Summary
Lolium rigidum Gaud. is one of the most common weed species in winter cereals in Northeastern Spain. Is one of the most common weed species in winter cereals in Northeastern Spain. To chlortoluron and diclofop-methyl has been reported in Catalonia since 1995 (Taberner et al, 1995). The problem has continued growing and more populations have been found resistant to tralkoxydim, fluazifop and chlorsulfuron (Taberner, 2005). The estimated affected area is still less than 0.5% of the 6 million hectares of winter cereal in Spain (Díaz and Gorrochategui, 2005) but the affected fields require costly management. Low cereal yields and selling prices have encouraged Spanish farmers to invest minimum efforts in their cereal crops spraying expensive graminicides only when the cheap ones failed. The current high cereal price situation may introduce new elements in this scenario modifying the prospects for herbicide resistance
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