Applying a T0 fungicide in winter barley to ‘damp down’ over-wintered disease could prove a useful management tool with increased areas of the crop in rotations this season, says one agronomy expert.
Although T0 is used commonly in winter barley in Scotland, it has also started to attract growing interest in England over recent seasons, particular in the wetter West. According to field technical manager for Syngenta Iain Hamilton, this has been driven by increased awareness of the importance of keeping lower barley leaves clean even before the first major fungicide spray at T1.
Four years of independent trials showed a clear reduction in rhynchosporium from a T0 mixture of cyprodinil with spiroxamine in high disease pressure situations, he says, with yield also boosted by an average of 0.3 tonnes/hectare (0.1t/acre).
With rhynchosporium, net blotch and mildew all seen in crops before Christmas this season, and larger barley areas to contend with in rotations, a T0 could give growers useful breathing space if the T1 spray is delayed, he adds, and help to keep crops in a more protectant situation.
“Lower leaves, even down to leaf 5, contribute significantly to yield in winter barley,” says Mr Hamilton, “but these are the leaves coming out of winter where disease tends to start.
“The T0 spray is about getting rid of this early disease, which makes later disease control easier – by reducing the risk of getting into curative situations at T1 and T2.
“It is important to manage the crop correctly so you are not chasing disease later in the season. It is about responding to the way barley produces its yield,” he adds.
As well rhynchosporium, net blotch and mildew, brown rust can also be a target for T0 in some cases.
Syngenta advice is to use a mixture of cyprodinil (Kayak) and a morpholine for the T0 timing. “As well as covering a useful range of diseases, this also uses different chemistry to triazoles, SDHIs and strobilurins which may be used later in the programme, for resistance management,” says Mr Hamilton.
In Scotland, Syngenta field technical manager Iain Anderson says T0 in winter barley is already well established as a management tool, and tends to be timed to coincide with the start of spring growth.
“You are clearing out over-wintered disease,” he says. “People sometimes think you can omit the T0 and just increase the triazole dose at T1 instead. But if rhynchosporium takes hold before T1, that can put you on the back foot, and you can end up chasing disease for the rest of the season.”