Two SDHIs get the green light for barley use

Two SDHI-containing fungicides are now cleared for use on barley this year, adding to the control options available. Louise Impey reports.

Two familiar fungicide brand names to many cereal growers – Adexar and Treoris – are now available for use on all barley crops, including those destined for malting.

In the case of BASF’s Adexar, which was already registered for barley, the new approval covers its use on malting crops. For DuPont’s Treoris, an extension of the label means it has been cleared for all barley crops.

See also Malting barley growers get more fungicide choice

For the BASF product, it is worth noting that the British Beer and Pub Association’s clearance to use Adexar on malting barley is for a total dose of 62.5g of the SDHI fluxapryoxad a crop, which is equivalent to 1 litre/ha of Adexar.

That’s half the full label rate of 2 litres/ha and means the product can be used at either T1 or T2, rather than both timings, and must be applied by GS45. Adexar is a mix of SDHI and the triazole expoxiconazole.

Existing choices

BASF’s Peter Hughes believes the main focus for Adexar will be at T1, where its performance matches that of existing choices.

Including it in a barley disease-control programme will also help to reduce the reliance on a very narrow range of fungicides – many of which contain the same active ingredient, he points out.

“It’s a convenient one-can solution, which can be used in programmes and won’t compromise disease control and crop performance. Its arrival also allows growers to mix things up and bring in other chemistry,” he adds.

Mr Hughes advises the use of 0.75 litre/ha at T1 in a low-disease situation, rising to 1 litre/ha where there’s more disease. Pyraclostrobin can be added to it where net blotch is a particular concern, he notes.

DuPont’s Treoris, which was registered for use on wheat last year, can now be applied to barley, including crops for malting.

A co-formulation of the SDHI penthiopyrad and protectant product chlorothalonil, it has a place at both T1 and T2, suggests Mike Ashworth of DuPont, who points out the chlorothalonil component adds to ramularia control, often required from the T2 treatment.

“Treoris can be mixed with whichever triazole the grower wants. In barley, that’s usually prothioconazole, which is the strongest of that group,” he says.

Nick Myers, head of agronomy at distributor ProCam, says T1 is the key timing in barley.

“The barley crop behaves differently to wheat and the main concern is to preserve tillers and maximise yield potential. It’s more difficult to do that later on with barley,” he says.

Mr Myers has seen good results from Adexar in barley, but adds that the other established SDHI mixes have also performed very well. “They’re hard to pull apart in a field situation – they all offer good activity on barley,” he says.

Very active

That’s a view shared by senior research scientist Jonathan Blake of ADAS, who has tested the various SDHI products in HGCA-funded fungicide trials over a three-year period. He reports the SDHIs are very active on barley diseases and that they are all very close in performance in the field.

“It’s fair to say that Adexar is a match. It looked stronger than the others on net blotch in 2013, but over the three years, that was evened out,” he says.

Bayer’s Siltra Xpro (SDHI bixafen + triazole prothioconazole) probably has the edge for ramularia control, he reveals, but otherwise it’s difficult to separate the leading contenders.

“There is a change of emphasis with Adexar, as the Xemium (fluxapryoxad) component is driving its performance, rather than the triazole component. In Siltra Xpro, the strength of prothioconazole comes through,” he says.

Andrew Flind of Bayer CropScience points out that the key strengths of SDHIs in barley are to add to the rhynchosporium, net blotch and ramularia control that are provided by the triazole.

“In a heavy-disease situation, you will see an improvement over the use of prothioconazole alone. On average, there’s a yield benefit of 0.25t/ha, but it’s likely to be greater than that in Scotland and Ireland,” he says.

Where early rhynchosporium can be an issue in winter barley, there is a case for using a SDHI at T1, while in spring barley – and particularly in the North – it makes sense to use the SDHI in the second spray, as it helps with ramularia control.