New fungicide chemistry is proving effective in UAP trials.

Trials investigating how best to use the three new carboxamide fungicides, in development, are showing that both T1 and T2 applications might be effective, according to UAP‘s Chris Bean.

“All the manufacturers seem transfixed with the T2 timing,” he told Farmers Weekly on a visit to the firm’s Kent trials site at Chris Stephen’s Rushborne Manor farm in Hoath.

But trials last season showed a 0.75t/ha yield advantage from using Bayer‘s BAYF869 (bixafen + prothioconazole) at T1 as well as T2, compared with just using it at T2 and applying a triazole + chlorothalonil at T1, he explained.

“It looks like it could be part of the programme twice, if we can afford to.”

If approved, the biggest use of the new chemistry would be at T2, he stressed. “And it will always be used in mixture with a triazole because of the potential for resistance to occur. Indeed, from what we can make out that will be part of the statutory label.”

As well as Bayer’s bixafen, UAP is also trialling Syngenta’s isopyrazam and another carboxamide from DuPont. The first two are currently seeking approval from the Chemicals Regulation Directorate, it was confirmed at Cereals, with their manufacturers hoping for approval in time for next season. DuPont’s fungicide is thought to be slightly behind the other two in the approvals process.

So far in trials this season the three look very similar in their activity when compared in mix with the same rate of the same triazole partner, Mr Bean said. “On last year’s evidence they are a couple of leagues above Tracker [which contains the carboxamide boscalid].”

In particular septoria control and green-leaf area persistence were impressive, he said. In one trial last year, two sprays of a carboxamide still had 50% green-leaf area in mid-July compared with 30% where two strobilurin sprays had been applied on top of the non-strobilurin programme, which had virtually no green leaf left.

“Using the right fungicide allows more natural ripening [rather than dying from disease] and, in theory, to increase yields as the photosynthetic ability is working for longer.”

Whether the new fungicides should be used in place of, or in addition to, strobilurins in wheat is one question the firm is trying to answer.

Strobilurins had proved particularly effective in helping milling wheats achieve the right protein specification, he explained. “Last year the only way we hit 13% protein on Solstice in our N/fungicide trial was by using the highest rate of N (320kgN/ha) and using two strobilurin applications.”

The two strobilurin sprays at T1 and T2 helped prolong green-leaf area and improve root growth from early on, he believed. “We’re seeing whether the carboxamides do the same, or whether we still need the strobilurins for that effect.”

But there was a definite benefit from using a mixture of triazole, strobilurin and carboxamide in barley, he noted.

T0 application

Many growers visiting UAP’s open days had admitted they wished they had applied a T0 fungicide this season, Mr Bean said.

That was particularly the case where yellow rust had been an issue, he said. “Where growers did apply a T0 they haven’t had problems with yellow rust.”

Most varieties showed an economic benefit from applying a T0 in trials last season, he said. In the most responsive varieties, Oakley and Zebedee, the yield response was nearly 1.0t/ha from a quarter dose of Capalo (epoxiconazole + fenpropimorph + metrafenone). “Even at £85/t you only need 0.13t/ha to break-even.”

Missing sulphur

Are you applying enough sulphur to your oilseed rape crops? Mr Bean wasn’t sure growers were. “I believe with low sulphur values in the soil and less deposition, not enough sulphur is being applied.”

To test whether oilseed rape responded to higher doses of sulphur UAP has been comparing the RB209 standard recommendation of 30kg S/ha with two higher doses of 60 and 90kg S/ha.

Last season’s results suggested there was a response to higher sulphur doses on fields yielding in excess of 4t/ha from applications of 220-250kg N/ha, he said. “I believe sulphur rates should be between 60 and 90 kg/ha as a standard unless you’re at the lower end of the yield scale. We’ve been getting yield responses down to 3t/ha.”

The cheapest way of applying extra S is as a blend with N, but liquid ammonium thiosulphate at green bud or 90-95% sulphur granules by the end of January are alternative methods.