Early season cleavers control proves key for yield saving benefit

UK - February 02, 2010



By starting their broad-leaved weed control programmes earlier this spring, growers are being advised that they could save themselves from significant yield losses in winter cereals this season.

A mean of four years of trials looking at cleavers control between growth stages 30 to 39, suggests that a loss of 2.2 tonnes per hectare can be expected in winter wheat by applying later weed control programmes.

That's according to Dow AgroSciences whose agronomist, Stuart Jackson believes there is still a mindset among some growers to leave cleavers control until late in the season when it is warm enough for the company's Starane 2 (fluroxypyr) to work quickly and reliably.

This approach will control the cleavers, he says but will not replace the lost yield, effectively costing the growers more in lost grain than any perceived chemical cost savings. "Cleavers is the most competitive weed in cereals and even 1 plant per square metre can lead to as much as a 3 per cent yield loss," he claims.

Looking ahead to weed control this spring, Mr Jackson believes that it's likely that cleavers, and other weeds, will have fared quite well in light of difficulties with weed control programmes last autumn. "Dry seedbeds resulted in reduced broad-leaved weed control from the pre-emergence herbicides and delayed the black-grass emergence, reducing the opportunity to apply Atlantis WG (mesosulfuron + iodosulfuron) in the autumn.

"It's likely then that a variety of weeds, including cleavers, will pose a considerable threat this season," he suggests.

In Dow trials during 2005-2006, with 37 cleavers per square metre, and with an untreated yield of 5.25t/ha, Mr Jackson says that Boxer (florasulam) applied at GS30 yielded 8.96t/ha, compared with a late season product applied at GS39, which yielded 7.16t/ha.

"Typically, 2t/ha was lost between GS30 and GS39. We're definitely seeing a yield benefit by attacking cleavers early," continues Mr Jackson. "Early season applications before GS32 consistently produce a better yield and subsequent margin over input than a late-season application."

He says that in situations where growers will be applying Atlantis WG in the spring, then it's possible to mix in 50 or 75ml/ha Boxer with it, and apply as soon as active growth begins at the end of February, or early March.

The tank mix of Atlantis and Boxer is approved by CRD, he adds.

"If you are going through with a sprayer anyway for an application of Atlantis WG, putting Boxer in at 50 or 75ml/ha is cost effective and doesn't complicate the tank mix," advises Mr Jackson.

"It tank mixes well with no additional restrictions to the following crop beyond those of Atlantis WG," he points out.

Alternatively, Mr Jackson says that those in non-wheat situations (i.e. winter barley), or for those that applied Atlantis WG in the autumn, a T0 timing of Boxer at 100ml/ha, or a T1 timing of Starane XL (florasulam + fluroxypyr) at 1.25l/ha, will ensure the cleavers are controlled before they compete with the crop at GS32 onwards.

If at the T0 timing the cleavers are still blue in colour, he advises growers to either increase the Boxer dose rate to 150ml/ha, or wait until active growth begins and then use 100ml/ha.

"GS32 onwards is when cleavers really start to compete and this is when we see the crop yield beginning to drop off if left untreated to the later timing.

According to North Lincolnshire-based Masstock agronomist Steve Portas, controlling cleavers early was the basis of a replicated trial undertaken at Masstock's Throws Farm Agronomy Research and Development Centre in Essex during 2008. A range of treatments was applied from December through to May, he says.

"For effective control of cleavers,  Barton (a highly concentrated, novel formulation of florasulam, the active ingredient in Boxer) applied in March, or two weeks' later in April, gave virtually 100 per cent control. However, due to the nature of cleavers competing with light and nutrients, crop yield was highest at the earlier timing in March (see Fig 1 below).

"In comparison with other treatments in March, Barton gave an extra 0.5t/ha yield due to its higher level of cleavers control in cool conditions, and good crop safety," he explains.

"It's clear however that cleavers need to be sprayed before growth stage 32 (the end of April) or a yield penalty occurs."

Trial plots contained 60 cleavers plants per square metre, putting intense pressure on the herbicides applied, he adds.

Later sprays for cleavers in May at crop growth stage 37, continues Mr Portas, not only gave poorer cleavers control and a reduction in yield, but also gave a reduction in specific weight in the crop.

"The highest bushel weight was achieved in March for the Barton treatment - almost 77kg/hl - down to 73kg/hl for a straight fluroxypyr treatment in May.

"In economic terms this equates to a loss in income of £220/ha from 2.2t/ha lower yield, and a penalty knock-off from a reduced bushel weight," he claims.

"In fact, the poorest treatment in March was better in money terms than any treatment in May - with 20 per cent of the cleavers re-growing from spraying at this late timing giving final control of only 50 per cent of the weeds."

Cleavers also interfere with harvest, and seed can contaminate the grain sample reducing marketability, points out Mr Portas.

As well as going in for cleavers, he says that Barton is also an excellent clean-up material after the autumn sprays on common broad-leaved weeds such as mayweed, charlock, runch and groundsel, which occasionally escape from the autumn residuals.
"Volunteer oilseed rape is also controlled and, with an additional wetter, volunteer beans too.

Steve Portas provides agronomic advice for the 2,000 acre Elsham Hall Farms, Wrawby, near Brigg in North Lincolnshire, a business which grows mainly winter oilseed rape, winter wheat, spring beans and winter rye.

Farm Manager, Andy Radley says that cleavers are particularly a problem on the heavy land, although numbers are reducing in some fields due to early season use of Barton.

"We've been using Barton for 3 years now, but at a much earlier spray timing than with previous treatments," he points out. "Following autumn residuals which gave us some useful control, we used to go after cleavers round about a T2 time with Starane, as it needed to be warmer for it to be effective.

"But going later in the season means higher dose rates are needed to kill the larger cleavers and the bigger crop canopy makes it harder to get the spray in," comments Mr Radley.

"Barton allows us to spray for cleavers in the earlier, and colder temperatures at GS30 and it's usually applied with a PGR which comes with a wetter, further enhancing control of volunteer beans and large charlock."

He believes the treatment has, on several blocks of land achieved almost 100 per cent cleavers kill, with little or no seed returning to the seedbank.

"Also, with hedge mustard a common problem in oilseed rape in some more recent land taken on, we look to use Barton to remove it in wheat.

"We're going in for cleavers anyway, so the extra cost is nil," he adds. "Using Barton has, in addition, reduced the amount of packaging we have to deal with."

Bill Jones, agronomist with Market Drayton based BCW Agriculture Ltd, says that he advises growers use Boxer in winter wheat at a March timing, usually in combination with a PGR, trace elements and a T0 fungicide spray, on predominantly light land in East Shropshire.

He agrees that the earlier the product is used, the greater the benefit to the crop in terms of yield. "In some situations we have here where there are a lot of cleavers carried over following a potato crop after min-tilling, then the principle of taking cleavers out early with Boxer has got to be right, and it will provide a yield benefit," he says.

Groundsel and volunteer oilseed rape are weeds that sometimes escape the autumn residual programme and Boxer is very effective on these, he says, which need taking out early as they grow rapidly in the spring when nitrogen is applied.

"If cleavers numbers are sporadic after potatoes, Mr Jones prefers the option of going with a later application of Starane XL to take out the cleavers as well as volunteer potatoes.

 

However, Boxer's broad-spectrum weed control is its key advantage, continues Mr Jones. "With the loss of IPU, we're going to see other weeds such as chickweed and mayweed becoming more of a problem, in addition to meadow grass, ryegrass and bromes.  "For us, black-grass is not the main issue, but Boxer has a better range of weed control compared with Eagle (amidosulfuron), which we used to apply, as well as having greater versatility in terms of tank mixing with other products."