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Talking Agronomy with Sam Patchett: Disease control tops the agenda


By the time you read this, fingers firmly crossed, our planned T0s should be getting to grips with the significant levels of septoria we are seeing in most of our well-grown wheats. 

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As we move into the second week of March, much of our ground is still too wet and our first wheats too forward for their first split of nitrogen. The next two weeks should see spreaders out in force, though, applying an initial 50-80kg N/hectare – depending on the crop – together with all the season’s sulphur.


Providing the clear warming currently evident is sustained, a good weed tidy-up will also be underway. Thankfully, there are far fewer grass-weeds in our crops than previous years despite little or no post-em spraying.


Septoria control is the number one wheat priority from here. Not least because rusts have yet to make an appearance and our variety mix has so much better rust resistance this season. Fungicides are always the single best investment we make. Last year, for instance, my Agrii colleagues’ northern region variety trials delivered an average margin over fungicide costs of more than £100/ha even with wheat at £60/tonne.


To counter the septoria sensitivity shift, I am combining multi-site protectants with stacked triazoles and SHDIs across this season’s programme. With the excellent results my growers and I got from doing so last season, we’re planning to use SDHIs at both T1 and T2 where crops and disease risks merit it. With trial work showing the extent to which stacked triazoles are pulling away from straights in disease control, yield benefit and margin over fungicide costs, all our main treatments will involve stacks. And, in line with the latest trial findings too, we’ll be using different stacked triazoles at each treatment where possible.

Septoria pressures

Where septoria pressures are high, a T0 wasn’t applied and/or stem-based diseases are a particular risk, my first choice T1 will be a mixture of prothioconazole, bixafen and spiroxamine. All three actives have activity against septoria and trials show good synergies between them – the addition of spiroxamine proving especially valuable.


For crops with a lower yield potential and where septoria pressures are lower, but stem-based diseases remain a threat, I plan to use the new SDHI, penthiopyrad supported by a robust prothioconazole + tebuconazole mix.


Where disease risks are the lowest and we can afford to cut-back on the fungicide input, we’ll probably go for a T1 combination of epoxiconazole and metconazole with folpet. However, wherever possible I’m keen to save this especially complementary triazole stack to partner the most active formulation of the most curative SDHI, fluxapyroxad at T2.


My preference in all cases is for proprietary triazole formulations rather than tank-mixes for their noticeably better uptake, activity and results; especially with deeper-seated infections like brown rust. Should either this or yellow rust become evident, of course, we’ll add a strobilurin to the T1 mix. And, workloads and weather permitting, we’ll get the spray on just as leaf 3 emerges to give it the greatest possible protection.


With noticeably slower early crop development, the ideal timing for T1 is likely to be a little later than last year.


Fungicides are also at the forefront of our mind for the oilseed rape just now, both for disease control and plant growth regulation.


Rothamsted is predicting 77% of crops in our region at particular light leaf spot risk this season – the highest on record. So prothioconazole and tebuconazole will be our primary weapons of choice. At the same time, I’ll be looking to the new PGR, paclobutrazol or good old metconazole to keep our larger canopies well in check. The cold weather has certainly helped, but we still have plenty of crops which could easily get too big for comfort.


Sam Patchett is an Agrii agronomist based in Yorkshire. He provides agronomy, crop nutrition and seed services to clients growing cereals, oilseed rape, maize and fodder beet across West and South Yorkshire and also helps run Agrii’s Brotherton R&D site near Selby.

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