IPU loss means alternative needed for meadowgrass control

If you’re going to use IPU and trifluralin this season the chances are they are already in your chemical store, or at least allocated to your farm.

For those without guaranteed supplies you will have to move pretty quick to find supplies for the autumn in what will be their last season of use.

All growers, however, should start making plans to cope with their loss, Tim Holt of Bayer CropScience suggested during a roundtable discussion with TAG‘s Jim Orson, Peter Riley of Prime Agriculture and Gilles Chevallier, campaign manager for Bayer.

In recent years much less IPU had been used for blackgrass, although 200,000ha of land with blackgrass problems did still receive IPU somewhere in the programme, Mr Holt pointed out.

But it is growers looking to control annual meadowgrass who will probably miss it most IPU dominated the market, he said. A number of alternatives were available including residual herbicides containing pendimethalin, flufenacet, chlorotoluron or prosulfocarb.


Most of them, with the possible exception of chlorotoluron, needed to be on earlier, either pre-emergence or just after, compared with the typical early post-emergence, meadowgrass at the two to three leaf stage traditional IPU timing, Mr Riley pointed out.

The IPU timing usually coincided with when growers would also be applying BYDV treatments, he explained, so a switch to earlier treatments would mean growers having to come back separately for BYDV or more use of insecticidal seed treatments.

“If you’re aiming to keep to a single pesticide application in the autumn, Deter dressed seed and a residual is a good option.”

But for many growers that would require a change in autumn strategy, with most not used to applying a pre-emergence treatment for meadowgrass. “A pre-emergence can be frowned upon – growers don’t like stopping the drill to spray it.”

The alternative to a residual is the contact material Othello. “Once there is tillering meadowgrass it is pretty much the only option,” Mr Holt said. The higher 1.0 litre/ha rate will control meadowgrass up to the second node stage (GS32). Bayer also has a 0.8 litres/ha rate for pre-tillering meadowgrass (GS13). “That will bring the cost down.”

Mr Riley used some Othello on farm last season. “One particular case was quite a test, early September sown wheat that had had no weed control until late November. Othello was quite impressive I see it as a useful introduction.”

Mr Orson’s only concern with the product was that it was another sulfonylurea. “We rely on sulfonylureas for broadleaved weed control, and there is a need to rotate actives because of resistance. We already have cases of chickweed and poppy resistance to sulfonylureas, so any sole adoption of Othello is a concern.”

The product did contain the residual diflufenican, he admitted. “That does mean my concern might be overstated, although DFF is weak against chickweed, but any over-reliance is something to think about.”

The big advantage of sulfonylureas was on certain weeds, such as groundsel, he added.

Using Othello was an alternative for growers who didn’t want to use Deter and still only spray once with a BYDV spray, Mr Riley said. The important consideration with timing was not to spray when it was too cold, as with Atlantis. “Late October / early November should be fine.”

Mr Chevallier said growers shouldn’t be afraid of going too early with the product. “We haven’t found we have needed to go back afterwards.”

Whichever route growers chose the good news was that it wasn’t difficult to achieve high 90s percent control of annual meadowgrass, Mr Orson said. “Having DFF as a separate active ingredient helps too, so it will come down to cost, convenience, timing and what broadleaved weeds you are also targeting, for which product you go for.”

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