A combination of knowing the biology of blackgrass and effective stubble management, can serve to greatly reduce the impact of the weed within cereal crops.
According to ADAS research scientist, Dr. Louise Cooke: “There is also a role for stale seed beds in getting to grips with blackgrass infestations.
“By using this approach, blackgrass seeds, which are allowed to germinate – can be sprayed-off with glyphosate.”
ADAS is the UK’s largest independent provider of agricultural and environmental consultancy, policy advice, and research and development.
Cooke spoke at the 2023 Teagasc Grass Weed conference. She confirmed that fundamental blackgrass management control centres around a particular question – do growers allow the weed seeds to emerge, or should they be buried?
“Crop rotation is also critically important when it comes to dealing with blackgrass. It’s a management approach that allows growers to use a range of different herbicides,” she added.
“Growing different crops allows for different sowing dates. This approach allows growers to minimise weed emergence. One of the most important aspects to the management of blackgrass infestations, is the growing of a competitive crop.
“Getting a new crop sown out in good conditions and getting it growing well is incredibly important. Weeds make the best use of bare patches – give them an inch and they will take a mile,” Cooke stressed.
Weed treatment
Cooke believes that blackgrass can also be tackled on a pre-harvest basis. “Burning it all out with glyphosate is one option. But why leave it until then? Approximately 80% of blackgrass weeds come up in the autumn,” she continued.
“From a control point of the view, this is the weed’s fundamental weakness. There will also be a 70% seed decline on an annual basis. In other words, within five years, it should be possible to get rid of the problem within the seed bank.
“Blackgrass seeds cannot germinate from depth. So, if they are buried deep, they will not emerge. The great strength of blackgrass is its power of contamination,” she explained.
“Another critical strength of blackgrass, is its high seed production capacity. The plant also thrives in wet conditions.“
Cooke explained that cultural control of blackgrass in the autumn can give very variable results adding that this approach is not a ‘silver bullet’.
“Ploughing is a very valuable control method, but it is expensive,” she added.
“However, once blackgrass numbers have been significantly reduced, a better response to selective herbicides will be achieved,” she said.