Mixmasters make comeback as triazole price rises bite
Mixing appropriate triazole cereal fungicides could help counter a 6% price rise and a resistance-driven higher dose requirement this spring, and get the best from newly-launched prothioconazole, according to agronomists.
Triazole “stacking” – mixing and matching two triazoles with different properties and strengths – is not new, says Agrovista”s technical manager Mark Palmer. “It”s going back to old tricks. We commonly used products like Sportak Delta to mix slow and fast moving triazoles in the past.”
That was in the late 1980s to mid- 90s. Then the practice waned with the advent of strobilurin chemistry, and the launch of a more effective triazole, epoxiconazole.
But matching fast and slow moving triazoles still makes good sense, according to Dalgety”s Peter Corbett. “Fast moving triazoles, and the classic example is flutriafol, are rapidly taken up by the crop.”
That can be a disadvantage if the product is used later in the season, as it can cause leaf tipping. But at T0 or T1 it allows the triazole to move within the leaf rapidly to where it is needed, he explains.
“Then you can match that activity by adding a slower moving triazole, which hangs around on the leaf surface, and offers much greater persistence.”
Prothioconazole is the slow-moving triazole favoured by Dr Palmer, in combination with “fast” cyproconazole. “Caddy has good systemicity, which is important at T1.
“The combination gives a nice blend of triazole – and an even distribution on and within the leaf,” he says.
An average 0.4t/ha yield increase from the combination over straight Proline across three Bayer CropScience trials give credence to the mix approach (see graph right).
“It”s a robust mix – and fits most varieties, primarily at T1,” he suggests.
Robigus, with its yellow rust susceptibility, might be the ideal fit. “Cyproconazole will boost prothioconazole”s yellow rust activity.”
Triazole stacking could save growers money, or at least allow them to boost triazole dose without increasing costs, says Mr Corbett.
“With Opus more expensive than last year, and Proline newly launched [at a similar cost] growers could use slightly lower rates and boost with another triazole to get the right amount of triazole units.”
That is particularly relevant with the shift seen in efficacy against septoria, he says. “The HGCA data clearly shows you need to use more triazole now to get the same sort of efficacy.
“But growers need to maintain costs at acceptable levels for the current grain price.”
Agrovista”s typical mix and match recommendation will be Proline at 0.3 litres/ha plus 0.12 litres/ha of Caddy, says Dr Palmer. “That”s similar on cost to half rate Proline, but delivers more triazole units.”
Triazole stacking isn”t just restricted to early season sprays, says University College Dublin researcher Tom McCabe. His work suggests combining epoxiconazole and prothioconazole is particularly effective at flag leaf.
“We got interested because of the performance of Bayer”s prothioconazole plus tebuconazole formulation. That has worked better than either straight Opus or Proline at T2.
“Opus + Proline makes a logical mix. Epoxiconazole”s curative activity is well known, while prothioconazole gives particularly good persistence.”
In trials, a half dose Opus plus various rates of Proline gives better disease control, particularly 6-8 weeks after application than full dose Opus (see table left), he says.
“The mix didn”t add much to curative control, but increased persistence, and was reflected in yields.
“Proline does seem to benefit from mixing at mid-season – it”s more positive than you would have thought, indicating some sort of synergy or at least complementary actives.”
