Don’t be tempted to drop pre-emergence herbicide applications, even though stale seed-beds appear to have been successful this autumn.
Damp weather during harvest has provided ideal conditions for blackgrass germination and stale seed-beds are carpeted with plants, says Lincolnshire AICC agronomist Sean Sparling.
“This means large numbers of plants can be taken out with glyphosate prior to planting, but growers shouldn’t use this as a reason for relaxing pre-emergence herbicide applications.”
“Don’t just plant and wait to see what comes up – glyphosate is a good start to the programme, but it needs to be followed with a robust pre-emergence programme applied carefully at the right time.”
This strategy will give robust control early on and follow up treatments of Atlantis (iodosulfuron) can be applied in late autumn if required, he adds.
To maximise glyphosate efficacy, ground should not be cultivated for at least 24 hours and ideally 48 hours after application, he says. “It needs to be fully absorbed and leaves should be dry before bringing cultivators into the field.”
Emerging oilseed rape crops are also covered with blackgrass and will need a robust post-emergence programme, he says. “90% of oilseed rape ground in this area was sprayed with glyphosate pre-drilling, but there has been a considerable flush since then which will need to be tackled with a graminicide.”
Stale seed-beds have been equally successful in Wiltshire, says Agrovista agronomist Peter Dews. “We had six inches of rain that coincided with seed shed so germination has been very good.”
Growers should take as many plants out as possible pre-drilling and consider two stale seed-beds in the worst fields. “We haven’t been able to batter the seed-bank for a few years so we should make the most of it.”
ADAS’s James Clarke agrees. “Getting rid of blackgrass pre-drilling is a good start, but there will still be significant numbers that will germinate post-drilling.
“If you’re going to miss one application, make it the post-emergence spray as you will be able to see the full picture by this point.”
Removing blackgrass early also reduces risk of resistance build-up, he says. “If you have a blackgrass problem and don’t have the resources to spray while drilling, you should stop the drill.
“At the moment it looks like with will be getting warm, damp weather for the next few weeks so it is an ideal opportunity to delay drilling and get second chit, if required.”
Watch out for volunteer cereals in OSR
The threat of volunteer cereals in newly emerged oilseed rape crops could be extremely high this season, according to one oilseed rape specialist.
This summer many fields suffered high levels of seed shedding and above normal combining losses in challenging conditions; a 1.5% loss on a 10t/ha crop equates to about 4.7m seeds/ha, said Gary Jobling, oilseed rape manager at Syngenta. That is roughly equivalent to double the typical sowing rate of a winter wheat crop.