Agronomist, Ken McTaggart says rapid N uptake means crops are particularly lush and reasonably thick, presenting a good environment for disease development.
Our winter crops are profiting from the great start to the spring the last two weeks of February gave us. As we move into the second half of March, both the wheats and the OSRs are responding well to their first splits of nitrogen and looking encouragingly clean and full of potential.
With the wheats fast-approaching GS30, early levels of septoria and mildew have subsided as the older leaves have died back. However, rapid N uptake means most are particularly lush as well as reasonably thick, presenting a good environment for disease development.
So, while they will not need significant curative attention with their T0s, we certainly are not taking anything for granted as we apply them in the coming week. Not least because we are so reliant on protective chemistry these days; the weather seems to delight in throwing us curved balls; and the last thing we want to have to do is bring our T1s forward to counter any upsurge in infections.
That would either mean risking an extended T1-T2 gap or going in with a T1.5.
Apart from anything else, our R&D colleagues saw a response of up to 0.6tonnes/hectare to a range of T0 programmes at their extensive Kent trials site last season. And the average response over a multi-site alone was 0.33t/ha.
For the less needy varieties we are using a co-formulation of chlorothalonil and cyproconazole with extra chlorothalonil to bring the rate up to 500g/ha. Where we have more resistance concerns, this is being replaced by a more robust metrafenone, epoxyconazole and fenpropimorph co-formulation with the CTL.
In both cases, we are including the mixture of trinexapac and chlormequat we have found works so well as the start to our PGR programme on the fairly fertile ground we have here in Kent. Especially so, as the Agrii Advisory List reveals that almost half of today’s 30 main varieties are noticeably weaker in the stem than their Recommended List scores suggest.
As ever, septoria will be our main target at T1 which should be going on about the time I am writing next month’s column. Because the Advisory List – based on the latest season’s trialling – also shows that many of the main varieties are more susceptible to rusts that the RL indicates, we will be making sure our combinations of SDHI, azole and multi-site give us adequate protection in this respect too.
With advanced tissue testing revealing lower-than-ideal levels of manganese, zinc and boron for higher-yielding crops like ours, we will be including these nutrients in the application together with our second PGR split.
Well into stem extension, most of our oilseed rape seems to have escaped the worst effects of flea beetle. We do have some issues with larvae in some crops, but very much in patches and at far lower levels than we have been hearing about from further west. So our combination of vigorous varieties and good early nitrogen should see them compensating well.
We have not been able to find any light leaf spot yet and, having moved to somewhat later drilling for more reliable moisture, we have less need for growth regulation than in the past. Added to which we have some decent resistance in our varieties.
This and the support of a well-targeted late-autumn fungicide spray, means we are only starting our spring spray programme at early yellow bud these days, using a combination of prothioconazole and tebuconazole.
Such an approach has worked well in recent years, giving us greater flexibility with our mid-flowering spray of boscalid supported by further prothioconazole and tebuconazole. It also gives us greater flexibility to employ late metconazole for canopy manipulation if necessary, as well as an insecticide to deal with pollen beetle if levels build-up.
And, of course, to include the magnesium, molybdenum and boron our tissue tests are again indicating we need. Early yellow bud has, indeed, become our key spray timing for OSR.