Biology and control of Bromus pectinatus Thunb
Wilcox, Douglas Howard
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Investigations into the biology and control of the annual grassy weed Bromus pectinatus Thunb. were conducted at the National Plant Breeding Station, Njoro, Kenya, from 1982 to 1984. Pot growth of B. pectinatus was influenced by soil type and microclimate, but not by seed origin. B. pectinatus was germinated and grown in amended and untreated soils ranging in pH from 3.05 to 8.13. Soils with a pH near 3 could not support growth or germination of B. pectinatus. B. pectinatus grew best on a soil of pH 6.55 and when soil pH influenced germination the optimum soil pH was 6.0. Exposure to light inhibited the germination of B. pectinatus seeds. Germination of B. pectinatus seed was most rapid at a 17 C temperature. Germination of dormant B. pectinatus seeds was enhanced by seed hull removal or pricking the lemma or removing the rachilla segment. Germination of B. pectinatus seed in the soil was unaffected by depth of burial, whereas, emergence was reduced to 35, 19, 11, 4 and 0% from depths of 0, 1, 2, 4 and 8 cm, respectively. There was a relationship between field emergence of B. pectinatus and the precipitation pattern. After-harvest germination of B. pectinatus seed indicated that there was an innate dormancy in hulled seed which persisted for 8 months. Field measurements were used to develop an equation which related yield loss in wheat with B, pectinatus infestation. Delayed sowing of wheat and barley into a B. pectinatus infested site resulted in yield reductions that were correlated with length of delay. Replacement series studies were conducted using varying proportions of wheat : B. pectinatus and rapeseed : B. pectinatus. Rapeseed / canola was unaffected by B. pectinatus interference. A spatial interference study determined that B. pectinatus interfers with wheat mainly above ground. The herbicides isoproturon, pendimethalin and oxadiazon were found to be ineffective against B. pectinatus, The herbicides triallate, chlorsulfuron, metribuzin, trifluralin and EPTC achieved limited control of B, pectinatus. Superior control of B. pectinatus was achieved using fluazifop-butyl at 0.25 kg/ha and fenthiaprop-ethyl at 0.12 kg/ha, in rapeseed / canola.