May 27, 2016
Vicki Brooks Blog: Managing the most important risks
Thankfully, we’ve been able to stay well on top of our most important pests and diseases while keeping a good tight rein on input costs so far this season.
A quick start to oilseed rape flowering in cold weather meant we didn’t need a single pollen beetle spray. We were also able to save a spray by combining our winter wheat T0 with a decent grass weed clean-up. And our spring cereals have developed nicely to four true leaves without unscheduled support.
As we go into May, though, the last thing we can afford is to let our defences slip; especially not with the serious disease and pest risks we continue to face.
Our biggest risk in oilseed rape is the prolonged flowering that looks inevitable with the dense, incredibly well-branched canopies we have. There are plenty of buds still to flower and these will be encouraged by some early pod losses courtesy of several late April frosts.
So we may need to follow-up our early flowering spray with extra sclerotinia protection together with additional light leaf spot control in such a high disease pressure season. We’re very much on seed weevil alert too, but we’ll only use an insecticide if we really need to and we’ll employ the safest possible product for bees.
Septoria remains by far our greatest winter wheat risk. A decent T0, cold April and timely SDHI-based T1 – just completed – have allowed us to keep it well away from the leaves that matter so far. However, my research colleagues have recorded more rainfall events this spring than in the very challenging 2012 season. So, even though an extended latent period means they’re not yet obvious, we know infections are poised to take-off as temperatures rise. Without adequate protection, they could easily explode in our faces.
Knowing this and with far less curative activity available in our chemistry these days, we’ll be going on with our T2s as soon as the flag leaf gives us a good enough target, even if this may only mean a two week gap from T1 in some cases. And we’ll be basing most – which should be well on by the time you read this – on a combination of a second SDHI with epoxiconazole and metconazole for the best green area preservation.
Cost is a vital consideration in our decisions here. But the risk from Septoria is so great that we cannot afford to get anything wrong at this stage or, like so many in 2012, we’ll find ourselves ineffectually chasing the disease at even greater cost later on.
With cost-consciousness to the fore, we’re including a specially formulated micro-nutrient mix with most of our T2 sprays to take advantage of the highly economic contribution Agrii research shows it can make to extending green leaf areas and maximising yields.
The major risk we’ve been battling in this season’s spring cereals is definitely slugs. The fact that they’re already grazing well-up in our winter wheat canopies underlines both the substantial populations surviving the mild winter and the favourable conditions of this spring.
Alongside this, with patches of BYDV obvious in our winter cereals, we’re acutely conscious of the need to counter a significant aphid threat with an effective spring cereal insecticide programme. Typical yield losses of 10-60% mean we’ll be targeting gout fly here too. This is another major threat we ignore at our peril.