“It fits really nicely as the first spray in either winter or spring-sown barley as it’s very active on scald, net blotch and rusts.”
Ramularia, the other big yield-robbing disease in barley in recent years, is better tackled later with an SDHI such as Aviator Xpro which acts as a second fungicide at booting-early ear emergence, Waddingham said.
“You can’t get at ramularia early and while Delaro will control it Aviator Xpro is the star against this disease. Using Delaro as your T1 buys you flexibity as to what to do later in the season.”
Fungicide Resistance Action Committee (FRAC) guidelines limit SDHI use to two applications a crop, hence the problem with using an SDHI early in the programme, Waddingham said.
“It means you’re limited to only one more later in the season because of the resistance risk. For high-yielding crops – and Warren Darling’s world record breaking crop last year was a case in point – you might want to use two SDHIs later, at growth stage 37 and at ear emergence.”
Crops where seed was treated with an SDHI have a similar problem in that they’re limited to one foliar application of SDHI because FRAC considers the systemic seed treatment equal to a foliar spray, he said.
The triazole-DMI (demethylation inhibition) component of Delaro – prothioconazole – is the active ingredient of straight formulation Proline and at Bayer’s recommendation of 0.75l/ha Delaro delivers 131g/ha of active, equivalent to just over 0.5l/ha of Proline.
“That’s a reasonably robust rate on barley and it’s got a lot of strob with it,” Waddingham said.
The strobilurin element trifloxystrobin will be familiar to growers from the old, straight formulation Twist. The advent of stobilurin-resistant strains of septoria in this country’s wheat means SDHI plus triazole-DMI chemistry is now preferred in that crop but Waddingham said in barley there’s still a strong case for a strob.
“Unfortunately the strobs have gone against septoria but they are still very active against scald and the strob means we have two modes of action in Delaro which from a resistance point of view is always a good strategy and enhances the disease control.”
Delaro will also be competitively priced, taking over from triazole-strob formulation Mogul (100g/l prothoconazole plus 50g/l fluoxastrobin) which is being phased out.
Waddingham said that Delaro will deliver a lot more chemistry per litre than Mogul did.
“It is an unfortunate fact that as the DMI fungicides [triazoles] are used for longer then slowly the amount of active ingredient required to control disease will increase, though we’re not seeing any shifts in barley disease control coming through yet.”
For lower-yield potential crops such as those on lighter, non-irrigated land or later planted irrigated situations, a two-spray Delaro programme could be a cost effective option, Waddingham said.
While Delaro has registration for use in wheat Waddingham’s advice is to look to the DMI plus SDHI combination Aviator Xpro (150g/l prothioconazole plus 75 g/L Bixafen) for the first and second spray, followed by the twin triazole formulation Prosaro (125g/l prothioconazole plus 125g/l tebuconazole) in mixture with a strobilurin fungicide for the ear spray.
“This year a high proportion of wheat was planted quite early which could well lead to higher septoria levels in the spring and you’ll need a programme that will really get on top of it. Aviator Xpro at T1 will do that,” he said.
DMI or triazole?
Triazole is the name for the largest group of fungicides that act by demethylation inhibition hence they belong to the wider group known as DMI fungicides. Imazalil, prochloraz and fenarimol are the non-triazole DMI actives.
There are also a few actives in the triazoles with names that disguise their triazole classification such as bitertanol, triadimenol and miclobutanil but most are easy to spot from the “-azole” ending.
