Saving possible but take care, warn experts…
Saving possible but take care, warn experts…
Herbicides. Costly cosmetic applications or essential
sprays? In this special feature we bring you advice that will
help you avoid the former and make sure you find the latter.
Sugar beet programmes for light and heavy land are
analysed, opportunities to reduce rates with adjuvants dis
cussed, and research into broadleaved-weed thresholds
relayed. Volunteer potato control in set-aside is tackled and
patch spraying developments reported. But first we examine
FAR techniques for beet and take a look at cereal weed
control this spring. Edited by Andrew Swallow
DELAYED drilling and spring cropping mean there are opportunities to make savings on herbicides this year, say agronomists. But extra care will be needed in unsprayed early sown crops as applications will be in the last dance, last chance category.
"There are some huge weeds out there and you are only going to have one chance at it," warns Procams David Ellerton.
Many broad-leaved weeds will require sulfonylurea products and sequences with graminicides must be carefully planned. Splitting applications is preferable wherever possible, he advises.
"Unless you have got resistance in the grass-weeds I would tend to knock-out the broad-leaved weeds first. You dont want a spring flush of wild oats emerging after the graminicide has gone on."
However, leaving grass-weed control to a later contact application could reveal some previously unrecognised enhanced metabolism resistance to fops and dims, he adds.
Where resistance to herbicides is known or suspected, then hitting it as soon as possible with as strong a mix as possible should be the number one priority, says UAPs Brin Hughes.
"Use the most robust treatment you can possibly put on. From the work we have done, that is Lexus plus a contact fop product such as Amazon or Hawk."
Adding an esterified vegetable oil adjuvant boosts efficacy. "They are kinder in multi-way tank-mixes than the mineral oils," he advises.
Where crops have struggled to establish, and resistant blackgrass has got away, growers should even consider ripping out the crop, or taking it as silage before the blackgrass heads, Mr Hughes adds.
Dr Ellerton warns that resistance is a risk growers should take into account with sulfonylureas, especially if they have already used one in the autumn.
"A lot of sulfonylureas are being used in a range of crops. Mix sulfonylurea use with alternative modes of action and make sure you get it right when you do use them."
Following-crop restrictions are another reason to make sure sulfonylurea labels are obeyed to the letter, he stresses.
Cleavers killers Boxer (florasulam) and Eagle (amidosulfuron) cannot follow Lexus, nor may new brome basher from Monsanto, Monitor (sulfosulfuron).
Hormone product withdrawal periods are another potential pitfall. "For example, only a 7-day gap is required after Topik before applying CMPP but if you apply the CMPP first you must leave a 14-day gap," says Dr Ellerton.
Late drilled crops are where savings can be made, he continues. "These crops will have much lower weed levels. Residual products such as ipu or Lexus should be reliable and could even see you through."
[Spring-sown crops provide another opportunity to lower chemical costs and clean up problem weeds with a stale seed-bed.
"Glyphosate is much cheaper than it was a few years ago. For about £2/acre you can save a lot of headaches later on."
[BOX]
CEREAL ACTION PLAN
* Untreated resistant grassweeds? Max dose ASAP.
* Beware SU sequence restrictions.
* Use residuals on latesown land.
* Glyphosate pre-spring drilling.
[as panel]
POLYGONUM POLICY
Hard frosts and open canopies could prompt unusually high numbers of polygonum weeds in winter cereals this spring, warns Du Ponts Martyn Rogers. "If you rush in with broad-leaved weed control too early you could miss a late flush coming through." Added to that some spring herbicides such as Ally are very weak on weeds such as black bindweed. Harmony M is a much better bet, he says. Procams Dr Ellerton echoes his warning. "These weeds can be extremely competitive and cause major problems at harvest. You have to be aware of them." [96]
CEREAL ACTION PLAN
• Untreated resistant grassweeds? Max dose ASAP.
• Beware SU sequences.
• Residuals on late-sown land.
• Glyphosate pre-spring drilling.