| dc.description.abstract | Investigations into the biology and control of the annual grassy
weed Rromus peatinatus Thunb. were conducted at the National Plant
Breeding Station, Njoro, Kenya, from 1982 to 1984.
R. peatinatus is described and, in the tradition of other Bromus
sp. of similar morphology, the common name Kenya Chess is proposed for
B. peatinatus.
Pot growth of B. peatinatus was influenced by soil type and
microclimate, but not by seed origin. B. peatinatus was germinated and
grown in ammended 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.
peatinatus. B. peatinatus grew best on a soil of pH 6.55 and when soil
pH influenced germination the optimum soil pH was 6.0. Out-of-doors
grown R. peatinatus matured earlier and had fewer culms than plants
grown in the shadehouse or glasshouse.
Exposure to light during germination, inhibited the germination of
R. peatinatus seeds. Germination of B. peatinatus seed was most rapid
at a 17 C temperature. Prechilling or preheating seeds did not promote
germination of dormant B. peatinatus seeds. Germination of dormant B.
peatinatus 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. The innate dormancy was mainly
induced by the seed hull, but was also induced within the caryopsis
itself.
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. Varying the
proportions resulted in growth changes in the plants. B. pectinatus
maturation was delayed when grown in a mixture. Rapeseed was unaffected
by B. pectinatus interference.
A spatial interference study determined that B. pectinatus
interfers with wheat mainly above ground.
The herbicides isoproturon, pendimetha1in and oxadiazon were found
to be ineffective against B. pectinatus. The herbicides tria11ate,
ch10rsu1furon, metribuzin, trif1ura1in and EPTC achieved limited control
of B. pectinatus. Superior control of B. pectinatus was achieved using
f1uazifop-buty1 at 0.25 kg/ha and fenthiaprop-ethy1 at 0.12 kg/ha, in
rapeseed. | en |
