Effects of chlorsulfuron on diclofop-methyl toxicity to Italian ryegrass (Lolium multiflorum) and Italian ryegrass interference in wheat (triticum aestivum)

Chlorsulfuron {2-chloro-N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino]carbonyl]benzenesulfonamide} and diclofop-methyl {methyl 2-[4-(2,4-dichlorophenoxy)phenoxy]propanoate} are herbicides used for the selective control of broadleaf and grassy weeds, respectively, in wheat (Triticum aestivum L.). The addition of chlorsulfuron (14.8 g ai/ha) to 0.90 kg ai/ha diclofop-methyl and applied postemergence reduced Italian ryegrass (Lolium multiflorum L.) control 27% and increased fresh weights over diclofop-methyl alone. Chlorsulfuron and diclofop-methyl were approximately 200 and 35%, respectively, more active on Italian ryegrass when applied pre-emergence compared to postemergence applications and responses of the combinations were additive. Although little movement of 14C-label occurred in either species, significantly more 14C-label translocated from the treated zone of Italian ryegrass. In metabolism studies, wheat was able to detoxify diclofop-methyl more rapidly than Italian ryegrass. In field interference studies, wheat grain yields were reduced an average of 4.2% for every 10 Italian ryegrass plants/m2 because of decreased crop tillering. Italian ryegrass had net nitrate and potassium influx rates approximately 2-times greater than those for wheat when plants were growing in nutrient solution in the greenhouse