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Field by field assessment needed for post-emergence herbicides in cereals
Date added: 30/11/09 |
Field by field assessment, for post-emergence grass-weed herbicides in wheat, are now being advised by ProCam Technical Director, Dr. David Ellerton.
He is also emphasising the need for the best application techniques to ensure that these herbicides are given every opportunity to work effectively.
“Herbicides such as Atlantis or Horus (mesosulfuron and iodosulfuron) can give excellent control of black-grass, meadow-grass, bromes, wild-oats and rye-grass and Broadway Star (florasulam and pyroxsulam) offers high levels of control of bromes, rye-grass and wild-oats. But only if they are applied correctly and on an individual field by field basis,” he says.
“You only get one shot at applying these products due to ALS sequence restrictions and so you need to get it absolutely right first time.”
Black-grass and other grass-weed germination this year started slowly in many areas, but once there was sufficient moisture many fields have developed a carpet of weeds, he says.
“The key message this autumn is to make sure that most, if not all, black-grass has emerged before applying contact-acting herbicides.
“There is a lot of variability in weed germination this year and the only way to find out if it is appropriate to apply herbicides such as Atlantis or the new liquid formulation, Horus, is to get out there and check.”
If black-grass is through and is at the 1-2 leaf stage onwards, then you can get started. But there are still a number of caveats. Always mix Atlantis/Horus with the adjuvant Biopower plus a residual, which will help with the stragglers that haven’t come through yet and add to longer-lasting control.
The residuals also add to the broad-leaved weed spectrum and help anti-resistance strategies. The main residual partners are pendimethalin-based and include Stomp/Cinder (pendimethalin), Orient (pendimethalin + picolinofen) or Churchill (pendimethalin + DFF), he points out.
“Other caveats include avoid applying if rain is imminent. Atlantis/Horus are rain-fast only within 2 hours. Avoid applying when the leaves are wet, or you’ll run the risk of run-off.
“If we are in the middle of a cold snap, hold off. This type of chemistry needs weeds to be growing for best performance and hence temperatures greater than 6°C are advised. Wait a few days after the cold spell before applying the Horus to enable active growth to restart.”
Dr. Ellerton also emphasises the need for good coverage of the target weed.
“Use sufficient water to get good coverage. Water volumes of 200 l/ha are generally better, especially if weed or crops are dense. 100 l/ha is acceptable but only if spray coverage is assured.
“Keep the boom height relatively low, around 50 cms above the crop. Increasing this to just 60 cms above the crop doubles the spray drift. Keep to a fine or medium quality spray and don’t travel too fast, between 8 and 12 km/h. Angled nozzles may help spray deposition.
“Spray conditions for Broadway Star are similar to those of Atlantis, although the main weed targets are different. Brome, rye-grass, wild-oats and a range of broad-leaved weeds being particularly susceptible. I would advise that the dose rate is kept up and an appropriate adjuvant used.”
If not already done so, David Ellerton advises growers to take the opportunity to add in a BYDV spray to these herbicides. Pyrethroids such as Alert, Hallmark (lambda-cyhalothrin) and Mavrik (tau-fluvalinate) offer good persistence.
He also warns to avoid mixing with chlorpyrifos for wheat bulb fly control.
“You need a gap of at least 4 weeks between the herbicide and the insecticide to avoid any risk of crop damage.”
Ends
PRM225
30th November 2009
For further information please contact Dr. David Ellerton, ProCam Ltd., Royston, Herts. Telephone: 01763 261592
Issued by Philip Hainey, Proterra Ltd., Stamford, Lincs. Telephone: 01780 756299 |
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