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Project description

Impacts of Time of Establishment and Irrigation on Barnyardgrass Phenological Development, Reproductive Effort, and Interference with Sugarbeets. (88CP012)
Program UC IPM competitive research grants program
R.F. Norris, Botany, UC Davis
Host/habitat Sugarbeets
Pest Barnyardgrass Echinochloa crus-galli
Discipline Weed Science
Commodity-Pest Interactions
Start year (duration)  1988 (Two Years)
Objectives Quantify the impact of date of germination and irrigation regime on phenology and seed production of barnyardgrass, Echinochloa crusgalli (L.) Beauv. The impact of barnyardgrass, as modified by time of establishment and irrigation, will also be determined for the sugarbeet crop.
Final report Experiments were conducted to determine yield loss to sugarbeets from competition by barnyardgrass, and to determine the growth of the grass weed and its seed production. A density of one weed every two meters of crop row caused only about 5% yield loss if it germinated with the crop, and had no consistent effect on the crop when it germinated later. When two barnyardgrass plants were present in each meter of row, sugarbeet yield loss occurred if the weeds emerged within 4 to 6 weeks of the crop. Barnyardgrass densities over 50 plants/m of row caused over 80% sugarbeet yield loss when they emerged with the crop, and still affected sugarbeet yield when they emerged up to 8 weeks after the crop. These results suggest that for typical barnyardgrass densities sugarbeets must be kept weed free for the first 6 to 8 weeks if loss is to be avoided. Barnyardgrass seed head size and seed production will be determined in relation to germination date and presence or absence of sugarbeets. Increasing density of barnyardgrass, in a second experiment, also resulted in increased sugarbeet yield loss. The magnitude of the losses were not altered by irrigation on a 7-day, 12-day or a 17-day interval. Barnyardgrass growth was, however, affected by its own density, the presence or absence of sugarbeets, and by irrigation frequency. Data on interactions with irrigation regime now indicate that seed production by the weed may be suppressed by longer irrigation intervals without compromising crop yield. This suggests that one way to minimize the build-up of the seed bank of the weed would be to keep irrigation frequency to the longest practical for satisfactory growth of the crop. Computer models of weed population predictions will have to be modified to allow for delayed emergence and for frequency of irrigation. Data developed in this research will permit necessary modifications to be made.

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