March 11, 2015
Disease control tops the agenda
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 our spreaders out in force, though, applying an initial 50-80kg N/ha – 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. This underlines the value of the Stow Longa recipe of delayed drilling into well-prepared seedbeds with robust pre-ems.
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. As we continue to see significant levels of Septoria in most of our well-grown wheats, I’m prescribing a good T0 wherever necessary towards the end of the month.
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/t.
To counter the Septoria sensitivity shift, I’m 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.
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 ai’s have activity against Septoria and Agrii 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. But, as ever, we’ll be keeping a close eye on progress as we know our wheats can fair rocket through their growth stages with sustained warm weather.
As can our winter barleys, which are also generally looking good – albeit with rynchosporium and mildew clearly evident in most cases. As usual, they’ll be coming to their T1s just ahead of the wheats. And with their lower leaves so much more important to yield, we’ll be employing what, in most cases, will probably be our only SDHI here. This will be partnered with prothioconazole and the spiroxamine that adds useful extra barley as well as wheat value.
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 LLS 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 that could easily get too big for comfort.
You can email Sam your comments and opinions via firstname.lastname@example.org.