Dormancy levels in black-grass are high this season with, on average, only 27 per cent of seeds received for testing, germinating, according to ADAS.
Black-grass has flowered and ripened earlier than in previous seasons. First samples were collected on June 22 in Cambridgeshire, over a month earlier than in previous years. Where crops were harvested early there is a greater opportunity for stale seedbeds, according to ADAS.
1. Spray off any black-grass that emerges before drilling - although less likely than in a low dormancy year. Germination from seed shed this season will be slow even where soils are moist – 90 per cent emergence will occur by 60 days after drilling.
2. Where black-grass populations high, consider ploughing. Good ploughing will bury this year’s shed seed to below the germination zone (top 5cm). But cultivations will bring up weed seeds from depth and these will germinate rapidly. Buried seed will remain in seedbank but decline by 70 per cent per year. However, after high levels of control in current crop avoid ploughing-up more seeds than you bury.
3. Early drilling and higher seed rates may be appropriate to encourage establishment of competitive crop.
4. Use robust pre-emergence herbicide with residual component to cover protracted period of emergence.
5. Apply robust post emergence herbicide programme. Time post-emergence sprays after most black-grass has emerged, applied at the correct growth stage and should also include a residual element.