As wheat crops continue to romp ahead and T1 sprays go on across the country, thoughts turn towards the flag leaf spray but agronomists underline importance of keeping to tight spray timings.
Sean Sparling, independent agronomist from north Lincs, is generally pleased with the condition of most of his wheat crops as T1 sprays have already been applied but warns that as conditions pick up crops will race on and will need careful watching.
The earlier drilled wheat crops are looking pretty well considering their condition a month ago. Disease levels are generally low; so far there has not been much evidence of mildew or eyespot although there is a little bit of septoria sitting on the lower leaves.
Very few crops received a true T0, so we went on slightly earlier than usual for the T1 to target leaf 4 as it is emerged. This spray was based on 1.25l/ha Tracker + 1l/ha azoxystrobin + 1l/ha chlorothalonil.
T2 will be aimed at the GS37-39 timing; this interval wont be stretched, and will include an SDHI, rate will be adjusted to disease levels at the time – the focus will be very much septoria and yellow rust on the more susceptible varieties.
Bill Barr of Prime Agriculture who advises on land in Bedfordshire and Northants, has got the T1s on his most forward crops. Crops around here are pretty variable, the early drilled crops are way ahead of the poorer backward crops that were later drilled into cold and wet soils. These earlier crops have held onto the tillers pretty well, but the later thinner crops are not as well tillered and quite short.
There has been very little sign of mildew or eyespot up to now. There is some septoria sitting on the lower leaves however and I have picked up on a fair bit of rust in the more susceptible varieties which will need attention.
Most crops managed to get a T0. Chlorothalonil is most definitely in the mix for T1 as continued protection against septoria but the lower disease levels have removed the need for an SDHI at T1, this will now be reserved for the flag leaf.
My T1 recommendations are based around a triazole + chlorothalonil, and where going on rust prone varieties I will include a strob such Comet. The T2 will be predominantly based around an SDHI such as Adexar but the rate will be dependent on how long the gap turns out between T1 and T2 crops will need careful monitoring as we race towards this crucial timing.
Nick Wall of Crop Management Partners based in Hampshire, says that managing the gaps between T1 and T2 will be critical. Some T0s around here in Hampshire only went on a fortnight ago with the T1s going on in mid-May, so the gaps are short we could be looking at flag leaf by the end of the month.
Whilst disease levels are generally low for now, what is worth watching is that because crops are still very prostrate leaves are rubbing against each other- so with this more recent rain septoria will move up the leaves and across plants very rapidly.
Mr Walls T1s are based around a Tracker type approach with chlorothalonil. The T2s will stay as planned based on an SDHI with rates being adjusted accordingly. If there is any sign of rust then I am confident that the Adexar will mop this up pretty efficiently.
Steve Dennis of BASF adds that the kick back activity of Adexar will prove to be really useful where timings are delayed as we move towards the flag leaf spray. You get much more curativity, more longevity of activity and better disease control with Adexar than we ever had with epoxiconazole.
The benefit of using Adexar is the flexibility in dose rates; in very low disease risk situations it is possible to go as low as 1l/ha if using the product preventatively. In higher risk situations and where curative activity is needed the rate should go up to 1.25 or 1.5l/ha.
Mr Dennis would always advocate the addition of 1l/ha CTL to Adexar offering not only a more robust treatment but as a means of resistant management. On the back of a high disease year in 2012, there is a focus on upping azole dose rates at the moment which is a good thing, but the first priority should be to use different modes of action with a robust dose of azole. Fungicide sprays should be well balanced delivering similar dose rates of multiple modes of action.
Its also worth noting that whilst Adexar is at the top of its game for yellow rust and septoria, it also provides good control of brown rust that could creep in towards the end of the season, and if disease levels are expected to be high, adding in some Comet at T2 will bring additional control and support crops that are becoming stressed.