Delaying cereal drilling until mid-October could significantly reduce ryegrass infestations, according to HGCA research.

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