Winter wheat trials in ryegrass-infested fields found that there were twice as many weed seed heads the following June in early (mid-September) sown crops, compared with the latest sown plots (mid-October).
The study also found that similar plant numbers emerged after mid-November following all drilling dates, so the additional heads in the earliest sown plots were largely due to the number of plants emerging before mid-November.
While delayed drilling would be effective, pre-emergence herbicides also had a significant role to play, especially against herbicide-resistant weeds, HGCA director of research, Graham Jellis said. “Post-emergence herbicides should be applied to small weeds.”
Recent monitoring studies had not supported the widely-held view that much ryegrass emerged in spring in winter wheat crops, he added. “The few plants emerging in spring will not thrive or set much seed in a vigorously growing autumn-sown cereal crop.”
Information on sustainable ryegrass control in winter cereals can be found in the latest HGCA Topic Sheet.
Ryegrass key facts:
- More competitive than blackgrass
- Five plants/ m2 cause 5% yield loss
- Approximately 20 heads and 5000 seeds produced per plant
- Delay drilling in bad ryegrass fields
- See HGCA topic sheet 100: Effective, sustainable Italian ryegrass control in winter cereals