Broomrape Control in Sunflower with Glyphosate

Sunflower (Helinathus annuuss IS a susceptible host to the holoparasite hempbroomrape (Orobanche ramosa) in central parts of Iran, causing yield loss due tosevere infestations. A field study was conducted in 2006 to evaluate the efficacy ofglyphosate for controlling the parasitic weed hemp broom rape in sunflower.Glyphosate was applied once or twice at five rates ranging from 0.075 to 0.450 kg aeha·1• Most efficient control was obtained from once or twice application of gyphosae at0.225 and 0.350 kg ae ha·1 at both application times. There were a significant reductionin hemp broomrape dry weight at 0.225 and 0.350 kg ae ha·1 (75 and 87.5 %),respectively compared to control. Glyphosate at 0.075 kg ae ha^- was not sufficientenough to provide acceptable control, but duplicating the application of this rateprovided good control of weed. Nearly no hemp broomrape shoot and dry weight weremeasured when glyphosate was applied twice at 0.450 kg ae ha^-1. However, sunflowergrain yield loss (63%) resulting from glyphosate toxicity at 0.450 kg ae ha·i wasobserved when applied twice, compared to its application at 0.225 kg ae ha^- Results showed that hemp broomrape was unable to survive after the twice applicationof glyphosate at 0.225 or 0.350 kg ae ha^-1