Weed management in common buckwheat (Fagopyrum esculentum)

There are currently no broadleaf herbicides registered in Canada for use in common buckwheat (Fagopyrum esculentum Moench.). Greenhouse and field studies were conducted from 1994 to 1997 at Morden and Brandon, Manitoba, to investigate potential herbicide treatments for buckwheat when cultural methods fail to control broadleaf weeds. Dose-response studies conducted in the greenhouse showed that buckwheat tolerance to desmedipham was three to five times greater than that of volunteer canola (Brassica napus L. and B.rapa L.), lamb's-quarters (Chenopodium album L.), redroot pigweed (Amaranthus retroflexus L.) and wild mustard (Sinapis arvensis L.). A separate experiment showed that buckwheat cultivars did not differ in tolerance to desmedipham. Another greenhouse study demonstrated that low dosages of bentazon caused severe injury in buckwheat. In field studies, 500 to 700 g a.i. ha−1 of desmedipham effectively suppressed the annual broadleaf weed biomass in buckwheat without reducing seed yields. At a low dosage of 300 g a.i. ha−1 of desmedipham there were no yield losses even though no weed biomass reduction was evident. Imazamethabenz at 150 to 250 g a.i. ha−1 and metribuzin at 140 and 210 g a.i. ha−1 severely injured buckwheat and usually reduced yields. 2,4-D at 140 g a.i. ha−1 suppressed weed biomass, but caused severe injury and often reduced buckwheat yield. At 70 g a.i. ha−1, 2,4-D suppressed weed growth as effectively as the higher dosage with less visual injury, but sometimes reduced buckwheat yields. Thus, desmedipham is the most promising postemergence broadleaf herbicide for use in common buckwheat. Key words: Common buckwheat, crop tolerance, dose response, weed management, yield