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Crop Advice & Expertise

What’s happening in fields in the Scottish Borders this June?

As rains return, Sean MacGill gives some tips on keeping on top of wheat disease and how to avoid crop safety issues when using late applications of herbicide

This month’s key messages:

  • Keep outstanding T2 applications robust as showery conditions return
  • Apply T3 fungicides at mid-flowering to protect against ear disease
  • Avoid compromising T3 timing by combining with insecticides for OWBM
  • Follow label guidelines for late grassweed herbicide applications to avoid crop safety problems

At my last time of writing, winter wheat growth stages were all over the place, but generally speaking, crops are now close or at the T2 timing as flag leaves emerge. Spring crops are looking a bit tatty, while oilseed rape has finished flowering and petals have dropped off.

Winter wheat

Last year the average wheat yield response in the Northern demo site was 2.75t/ha across 35 varieties, in a season that had similar moderate disease levels that are currently showing after a dry start to May.As the rains have returned at the start of June, disease levels will now start to show where it has been incubating in the plant.

Flag leaves contribute approximately 40% to the overall yield and the T2 application will be the most important fungicide timing and determine the profitability of the crop. T2 fungicide applications applied to clean leaves in the dry period may have been at a lower dose due to the lack of visible disease on the leaf.This may prove to be false economy, as the current weather conditions are ideal for development of Septoria.

For outstanding T2 applications, Ascra (bixafen + fluopyram + prothioconazole) at 1.2L/ha provides the necessary 75% dose of prothioconazole and two SDHIs to provide complimentary activity on a wide range of diseases.

Many wheat crops in the North received their T1 fungicide later than planned and some growers have discussed delaying the T2 application as a result.Ideally, the gap between the T1 and T2 application should be no longer than 3-4 weeks depending on conditions and variety.Septoria control is now regarded as a preventative application only, so treatment at the earliest opportunity is vital for success.

Ear disease complex

Consideration for the T3 treatment will focus around the ear disease complex, including Microdochium and Fusarium pathogens, and resulting grain quality issues which may arise.

There is still a significant yield contribution at stake with this timing, with up to 20% yield loss possible in worst cases.

Aim to apply mid-flowering to achieve best results and consider the many tank mix options available, including micronutrients, which may help raise grain quality. Orange wheat blossom midge (OWBM) insecticides are applied before flowering, so it is generally too late to apply with the T3 fungicide. If the insecticide is required, split the applications apart to avoid compromising either timing.

OWBM hatch begins as wheat approaches susceptible growth stages

Grass-weed herbicides

Despite many crops being around GS 39, I am still getting calls enquiring about the possibility of late herbicide treatments where fields have been overlooked or recent rain has triggered a late flush of grass-weed. Generally, it is too late to achieve good control, but where the label allows, it may be possible to stop some grass-weeds developing any further. These last-minute applications can also prevent seed heads becoming viable and reduce seed return to the soil. Brome is the most widespread problem in the North and it is clear this season it has been a challenge to control where spring sprays were delayed due to the catchy conditions.

Crop effects are likely with late applications, as larger plants absorb more herbicide and leaf tipping is common. Do not tank mix anything but the wetter (Biopower) for mesosulfuron-based products and use a min water rate of 150L/ha to penetrate the crop canopy and get good coverage onto the grass-weed target. Apply to a dry leaf to reduce run off, which is most likely to be later in the day. Also avoid hot bright days where possible.

This combination of do’s and don’ts does sound very restrictive, but such applications are always going to give more problems to solve than those applied earlier in the spring, but can offer a solution to some late emerged weeds.

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