Neil Buchanan: Frustration as weather compromises treatments

Article taken from the Arable Farming

Spring can be awfully frustrating when the weather decides to turn against you.  Input timing remains a key part of our role and already some treatments are being compromised.  It is easy to see the scars of deep-rutted tramlines across many fields in an attempt to salvage some degree of timeliness.

Planting of spring crops has also turned into a protracted affair, where ground just struggles to dry out and soil temperatures seem unwilling to start rising.  We are well into April and many acres of pulses and spring barley still remain in the bag.  They desperately need good seedbed conditions for rapid establishment in order to compensate for a shorter growing season.  Mauling in spring crops only ends in tears, better to be patient.

Cereal disease control programmes are well underway, with T0s completed and hopefully T1s by the time this reaches you.  No one disputes the high disease threat this season and many column inches have been given over to outlining robust defence strategies to deal with this situation.

The critical importance of timings, checking target leaf emergence, matching intervals to chemistry persistence in order to create that seamless programme of cover – it is all well documented and understood, but the universal key message of using more multisite inhibitors has proved somewhat difficult to achieve.  A distinct lack of product at the appropriate time has proved awkward to explain or justify.  Enough said.

Where beans are starting to emerge, there is already evidence of weevil attack and this will only increase as temperatures rise.  Characteristic notching from feeding adults is easily recognised, but the assumption this is the main damage is wrong.  Egg laying and the subsequent larval migration to the root nodules are far more serious.  Attention to threshold levels and appropriate use of premium pyrethroid is well justified, and even more so with the later drillings occurring this season.

Be vigilant for an early outbreak of downy mildew which normally requires treatment.  This is particularly relevant with some of the newer varieties which are exhibiting a disappointing downturn in resistance.

Annual battle

Oilseed rape is just starting to throw its first flowers and soon large swathes of the countryside will be yellow, but before that happens we are currently waging our annual battle with pollen beetle.  Migration into crops was slow to start, but a sudden hike in temperatures altered this fairly swiftly.  I suspect this rapidly increasing invasion will allow one treatment to be sufficient, but be mindful of threshold numbers and make those decisions away from the headlands.

Staying with OSR, next up is decision time for sclerotinia strategy.  The growing costs of this crop are already under close scrutiny and this disease represents the last big spend, so we need to get it right.  Use the monitoring schemes wisely and keep an eye on soil temperatures upon which germination of sclerotinia depends.  Programmes should aim to cover the flowering period and have started before any significant petal fall.  In most cases two sprays are needed to achieve this.

Success is very much driven by correct timing as treatments only protect, they are not curative.  Don’t underestimate the role application can play in this instance.  Your target is situated well down in a thick, tall crop, so adapt your sprayer settings accordingly.

Agronomist facts

- Neil Buchanan is an Agrovista agronomist based in Shropshire.  He advises clients across the West Midlands, growing cereals, oilseed rape, pulses and potatoes.


01 May 2015

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