Two familiar herbicides, isoproturon (IPU) and trifluralin, will be withdrawn next spring. Andrew Blake gauges Farmers Weekly Barometer farmer reaction

SOUTH WEST

IPU and trifluralin will definitely be missed at North Farm, Horton in Dorset.

“They’re the foundation of our herbicide strategy in cereals and well-priced,” says Peter Snell. “We’ve used them year in year out on pretty much all our winter wheat and winter barley, supplementing them with Stomp, Crystal and DFF.

“We’ll use both this autumn since we are allowed to until March 2009.

“IPU is good on annual meadowgrass particularly, but also chickweeds and other broadleaved weeds. It partners DFF and Stomp very well and is good value.”

Trifluralin is important in that there is no known blackgrass resistance to it, stresses Mr Snell. “What else can claim this?”

His longer-term mainly grassweed-driven plans include:

• For blackgrass: Pre-em Crystal or Liberator. Post-em CTU (on tolerant varieties) plus Stomp – avoiding Atlantis until really necessary.

• For ryegrass: Crystal plus CTU.

• For brome: Ploughing plus Liberator or Crystal pre-em. Plus autumn Atlantis if blackgrass still emerges after pre-em.

“Defy could fit into this strategy,” he says. “It’s good on ryegrass and could offer some saving over flufenacet alternatives. Avadex, another option, requires specialist application equipment.

“For non-blackgrass situations we could try Othello.”

Without IPU and trifluralin Mr Snell anticipates a 25-50% increase in weed control costs.

SOUTH

Losing IPU and trifluralin won’t be disastrous at East Lenham Farm, near Maidstone, Kent.

“But we’ve been using them on about half our area,” says Andy Barr. “So we’ll definitely need to alter our strategy, and there’ll be some increase in costs.

“The effect on resistance remains to be seen, but commonsense says the more actives we have available the better.

“In oilseed rape we’ve used trifluralin mixed with Novall on land prone to poppies to improve control. Our buying group, Crop Advisors, has secured a supply for this autumn and I have it in the shed.

In future the dimethenamid-p in Shadow and Katamaran Turbo promises improved control over metazachlor and quinmerac alone, but probably not as much as Treflan and will cost about £5/ha more (at last year’s prices), he calculates.

“In wheat we’ve used Treflan with Liberator pre-em in the worst blackgrass situations hoping for slightly improved control with a different mode of action.

“Here we may well use Defy to partner the Liberator instead at an extra £5-15/ha depending on the rate. Similarly, a Liberator + Stomp mix would be an extra tenner over the Treflan mix.

“In less demanding annual meadowgrass situations we’ve used IPU plus a picolinafen product.

“We could use CTU instead, at an extra £3/ha. But we’re growing Cordiale and Humber, which are intolerant, and Viscount, which I haven’t found any sure data for yet.

“So we may be forced down the route of more expensive products or using even more pendimethalin.

“The autumn barley approach will need a definite and expensive change from an IPU/Stomp mix to Axial/Stomp, which could add £20/ha.”

His oats, on which he has been using trifluralin-containing Uranus, pose another problem.

“The options with oats are limited, to put it mildly. So I’ll have to be even more careful where I grow them. Fortunately, I have product in the shed for this autumn.”

WEST

Will IPU be missed at Chillington Farm, Codsall Wood, Wolverhampton?

“The simple answer is, yes,” says Andrew Blenkiron. “Although we did manage without it last year.”

Trifluralin’s loss on oilseed rape will potentially reduce grassweed control and require higher rates of pre-ems, especially on the farm’s many fields where poppies are a problem.

“The loss of IPU on light land is mainly a costs issue, as I cannot find a mix as cheap as 1 litre/ha each of Javelin Gold and Stomp, which last year was about £4.50/acre.

“Having said that, grassweed control, especially of meadowgrass, is superior with Crystal, and I reckon we can potentially get the rate down to 1 litre/ha on the later sowings with either Hurricane or Graduate.

“Our agronomist, Bryce Rham, pushed us into life without IPU last autumn, so we’re ahead of the game in terms of what does and doesn’t work. It’s been a useful, albeit a bit more costly, learning exercise.”

The main reason for using IPU has been for annual meadowgrass control, says Mr Blenkiron. “But it also did a lot on chickweed, mayweed, was useful on poppies and had some autumn activity on wild oats.”

To date resistance has not been a problem at Chillington.

Looking ahead the farm’s replacement programmes are likely to involve Crystal plus Hurricane/Graduate, Defy plus Graduate/Flight, and Tolurex plus Flight/Hurricane, depending on crop, weed pressure and varieties.

“We have to remember that we can use Tolurex only on specific varieties, although I’m sure all of ours are OK.”

Othello, particularly on wheat after beans, worked very well at 0.5litre/ha with Duplosan last autumn, he says.

“I already use Crystal on all September wheats as a matter of course for much better annual meadowgrass control.”

The main increase in cost will come in October-sown crops, where Javelin Gold plus Stomp was “perfect”.

“I’m reckoning on spending £2.50/ha more on these crops, depending on how low a dose I can get the products to work at.”

MIDLANDS

Having used IPU and trifluralin widely at Thurlby Grange, near Bourne, Lincolnshire, Tony Reynolds will certainly miss the economic weed control they offer.

“They’re of the utmost value, and after March 2009 we lose the best chance of prolonging the longevity of Atlantis before resistance overcomes that chemical, which, if I understand correctly, is our last chance for several years to come. The real problems are a season away.”

Both herbicides have been used on about 80% of his wheat area, either pre-em if the drill slots have closed satisfactorily or early post-em if not. The main targets are blackgrass and broadleaved weeds plus wild oats in some fields.

But they have always been used in mixtures for example, Regatta plus trifluralin, he notes.

Blackgrass resistance is already a concern at Thurlby. “The big worry is the loss of alternative chemistry after next March.”

“We have considered products such as Othello, but feel it will compromise the use of Atlantis later.

“We don’t expect much change in costs this coming season, but after that the only way appears up.”

CTU as an alternative must have a future role, he believes.

“We hope the varietal implications will become clear after the 08/09 trial results are to hand before decisions for 09/10 have to be taken.”

SCOTLAND

For Mike Eagers IPU has been “the backbone of annual meadowgrass control on winter cereals” at Trinlaymire Farm, Linlithgow, particularly as a back-up to pre-emergence sprays on early-sown wheats.

IPU has added contact activity on “rampant” meadowgrass giving more timing flexibility and allowing the weed to be taken out up to early tillering, he says.

“We haven’t used trifluralin for at least five years.”

Firebird, Trooper and CTU seem the alternatives.

“If the weather doesn’t allow timely treatment of those and meadowgrass gets established we can always turn to Othello.”

Overall, he estimates weed control will be 15-20% more expensive once IPU goes.

N IRELAND

IPU has been “a very important pillar” in controlling the most persistent weed on James Wray’s farm, namely meadow-grass.

“We’re very lucky as blackgrass has not yet made it across the Irish Sea, but we do find meadow-grass a real problem.

“It can build up rapidly, seriously affecting yields. And in a wet season it really slows crop drying.”

His substitute is likely to be Defy plus Hurricane.

“I can use this mix on both winter wheat and barley to give me a broad spectrum solution in most situations. It can be used up to three leaves of annual meadow-grass, providing timing flexibility.

“It should also control cleavers and chickweed, two other important weeds here.”

Active ingredients

Atlantis iodosulfuron + mesosulfuron

Avadex tri-allate

Axial pinoxaden

Crystal flufenacet + pendimethalin

CTU chlorotoluron

Defy prosulfocarb

DFF diflufenican

Duplosan mecoprop-P

Firebird diflufenican + flufenacet

Flight pendimethalin + picolinafen

Graduate diflufenican + flurtamone

Hurricane diflufenican

IPU isoproturon

Javelin Gold diflufenican + isoproturon

Katamaran Turbo dimethenamid-P, metazachlor + quinmerac

Liberator diflufenican + flufenacet

Novall metazachlor + quinmerac

Othello diflufenican + iodosulfuron + mesosulfuron

Shadow dimethenamid-P + metazachlor + quinmerac

Stomp pendimethalin

Tolurex chlorotoluron

Treflan trifluralin

Trooper flufenacet + pendimethalin

Uranus linuron + trifluralin