With dry conditions easing disease pressure, there is an opportunity to reduce fungicide spend with a protectant-based T1 on winter wheat crops where septoria tritici is confined to the base of the crop, say advisers.
According to online portal CropMonitor, crops have developed quickly over the last week and many winter wheat crops have their final leaf 3 emerging. Septoria remains the main threat but is confined to lower leaves. Yellow rust, brown rust, mildew and eyespot levels, if present, appear to be at low levels.
ADAS senior research scientist Dr Jonathan Blake suggests there is scope for reducing fungicide spend at T1 this season where the least disease-susceptible varieties are being grown, on later sowings, and where disease is confined to the base of the crop.
He says: “Savings can be achieved either by reducing the rates of the SDHI/azole component by 20 or 30 per cent, or by omitting the SDHI component altogether.
“In all situations, the multi-site fungicides should remain part of programmes, as these products are ideally suited to protectant T1 situations such as this. The exception may be where yellow rust is highly active, where chlorothalonil can compromise azole activity.”
Bayer CropScience commercial technical manager Gareth Bubb also believes T1 applications should be protectant-based this season.
Bayer variety trials in high disease pressure last season showed plots treated with an azole + chlorothalonil (CTL) mix at T1 performed as effectively as those with new-generation SDHI’s, following a well-timed T0.
He says: “Those plots with robust and well-timed doses of Proline [prothioconazole] + CTL at the T1 offered the same disease control and yield response as those which featured Aviator Xpro [prothioconazole + bixafen].
“If you are in a protective situation [and use an SDHI] then you are paying out for enhanced curative activity which you do not need.
“We are still seeing Proline give 60 per cent control of septoria providing it is used at a three-quarter rate. Add in CTL and used sensibly in programmes and that increases to about 85 per cent, about what you can expect from an SDHI.
It is possible to obtain good control of septoria, yellow rust and stem-based control without the need to upgrade to premium SDHIs, says Mr Bubb.
“At T1, canopy expansion is only just beginning and the plant is not developed sufficiently to optimise the benefits of this new chemistry. The T1 is all about protection and you will not see the return from upgrading to an SDHI unless you have already got established disease.”
However, an azole + CTL mix may not be as effective if the T0 was compromised. If this was the case, the curative properties of an SDHI will be needed.
Agronomists report T1 applications are under way or about to start.
In the South, independent agronomist Richard Cromie, who advises across Hampshire, West Sussex and Wiltshire, says growers are up-to-date with T0 and have made a start on T1s. Disease is present in early crops but is starting to die back because of warm, dry conditions.
In Suffolk, independent agronomist Mike Warner says growers in the east of the county will not begin T1 applications until the end of the month. Mr Warner says disease is ‘not concerning’ following good control achieved at T0.
In Lincolnshire independent agronomist Ruth East says leaf 3 is only just peeking out. She expects growers to be spraying T1s towards the end of the month. Disease levels are low, with septoria drying up, she says.
Over in the West, Bayer CropScience commercial technical manager Gareth Bubb says T1 applications to forward crops got under way last weekend, but most growers are expected to make a start this week.
This season Bayer CropScience is running time lapse trials, with automatic cameras taking images every 15 minutes of a fungicide-treated and untreated plot of Santiago.
Sites at Great Chishill, Cambridgeshire, and Callow, Herefordshire, will be monitored, with the aim of assessing disease development as well as how environmental factors can affect development.
The treated plot at Callow received its T1 this week, and has septoria evident on leaf 5 and a small area of leaf 4 as well, says commercial technical manager Gareth Bubb.
However to date, cameras are not picking up any difference in plots because the T0 was only applied two weeks ago and effects are not yet visible, he adds.
For more information on the trials, click here