Crop Watch: Timing key to success with the sprayer

Making the most of the chemical can means knowing when to spray, and also when to hold off.

Our agronomists have a variety of advice this week on where patience will be a virtue.

Don’t rush on with an insecticide to treat pollen beetle unless the damage threshold is crossed, says Sean Sparling in the East, as taking them out also slashes the numbers of other helpful pollinators.

Down in the South, Iain Richards says a welcome lack of yellow rust means there is no need to bring forward any T0 applications, which will mean more time for other jobs.

See also: Cover crop lifts spring barley yields by 30% in grower’s trial

Andy Goulding says growers in the North have been holding off with their grassweed control until recently as overnight temperatures have been too low, but it’s getting under way now.

Although there is septoria present on older leaves on winter wheat crops in the wetter West, Stephen Harrison says there will be no yield benefit from treating the disease until T0.

East: Sean Sparling

AICC/SAS Agronomy (Lincolnshire)

Sean Sparling

Sean Sparling

With well over 60mm of rain, it hasn’t necessarily been the wettest March I’ve recorded, but it has been one of the most disruptive patterns of weather.

Oilseed rape is now receiving its final nitrogen dose and crops are widely at yellow bud to first flowers.

It’s worth remembering that only if thresholds are breached should insecticides be applied to treat pollen beetles.

Oilseed rape produces more than enough flowers to compensate for moderate levels of damage and tiny parasitic wasps and other predators within the canopy will thrive and do our job for us if we can just hold our nerve and leave the insecticide in the shed.

On my 2,000 ha or so of OSR, I haven’t sprayed more than 30ha/year in the past 13 seasons – the need has not arisen.

Disease levels remain relatively low although the past seven to 10 days have seen a noticeable increase in light leaf spot levels.

Thankfully the 1:7 plants affected threshold hasn’t been close to being breached, and imminent fungicide applications will provide further protection.

Less than 10% of sugar beet drilled

Sugar beet drillings are as widely delayed as I’ve seen them, and as of 27 March, less than 10% of my 1,200ha was in the ground.

Ethofumesate will be used as part of my pre-emergence programme, particularly where blackgrass features, but with only 1kg/ha of active ingredient allowed it will have to be taken account of in the post-emergence program.

The most important part of blackgrass control programme for me is the glyphosate before we drill.

Spring beans and peas continue to be drilled when the weather and seed-bed conditions allow.

With post-emergence weed control options so limited in these crops, it is vital the pre-emergence herbicides are applied as a priority once crops are in the ground.

And remember, peas and beans do not like going into soaking wet seed-beds as the foot-rot that will undoubtedly appear over the coming weeks will attest to.

South: Iain Richards

Agrii (Oxfordshire)

Iain Richards

Iain Richards

With a lot more spring barley to go in this season, some surprisingly wet ground, much of the oilseed rape taking off like a rocket over the past two weeks and urgently needing more nitrogen as well as its stem-extension spray, things certainly aren’t more relaxed for us at the moment.

Being faster developers, the vast majority of our rape crops are moving into green bud, with some distinct yellowing to their main racemes.

For the first time in three years, many are needing serious steadying.  

Early Toprex (difenoconazole + paclobutrazol) is balancing up our most forward pieces really well.

But those only just being sprayed are getting robust rates of metconazole.

With healthy 20-30 plants/sq m populations from our low hybrid sowing rates and remarkably little light leaf spot, this should really encourage them to branch out and fill the space available.

With such rapid crop development, we’re looking to the stem extension spraying to even up flowering, too.

Otherwise, we could be in for a serious sclerotinia challenge. However, it’s an ill-wind (quite literally) here.

Going in at yellow bud, as rapid growth and the unsettled weather looks like forcing us to do in many cases, should give a useful start to controlling this threat with combinations of metconazole and boscalid, in particular.

Don’t forget micronutrient applications

With this, we’re including a good dose of foliar magnesium and boron to address the clear magnesium deficiencies showing-up with such rapid spring growth and generally low levels of boron revealed in our tissue testing.

And we’re keeping a close eye on pollen beetle numbers which are building-up, although not at threshold levels yet.

Other than Toprex, one thing that has had a very noticeable early plant growth regulation effect this season – alarmingly so, in fact, has been bifenox.

Crops haven’t waxed-up nearly as well as usual in the on-off winter. So, despite timely spraying, the main racemes of some less waxy varieties have really suffered.

Although our wheats are also moving along nicely, they still have a good week to go until leaf four emerges.

This and no yellow rust to speak of is hugely welcome in avoiding the need – or temptation – to go in early with any T0s.

Thank heavens, as we’ve plenty enough on our plates just now with the OSR spraying and spring barley drilling without having any extra workload worry.

North: Andy Goulding

Hutchinsons (Cheshire)

Andy Goulding

Andy Goulding

The recent spell of frosts has kept leaf emergence retracted and crops are only just reaching T0 leaf four, even the crops high up the welly.

Septoria on later planted crops isn’t overly rife and yellow rust is only just starting on susceptible varieties.

Most crops will be receiving chlorothalonil at this timing other than crops where rust is active or expected, in which case an azole or strobilurin will be used.

Yield response isn’t the expectation with the T0 in regards to septoria control but with diverse cropping, mixed enterprises and high rainfall it is an invaluable management tool to give us a degree of flexibility with T1 timings where needed.

Barley on light land is still showing some slight manganese deficiency. It is important well-formulated products are used to address this, rather than relying on a large dose of an element and presuming it will all get into the leaf before recrystallizing.

Cleavers need tidying up

With high fluctuation in temperatures from teens in the day to minus figures in the night, grassweed control has been withheld – but is resuming again now.

Broad-leaved weed control has been exceptional with autumn residuals this season, with only cleavers wanting to be tidied up at this stage.

New active Halauxifen-methyl has made this decision easier with its good performance in low temperatures.

Conditions in the main have quickly become fit for spring crop planting, with everybody flat-out on all crops on whatever land is available for cultivation.

The workload is condensed at the moment with plantings, fertilising and crop-protection products being applied.  

Ground for maize production is also being prepared with manure applications.

With much heavy trafficking on this land it is important to dig to depth, assessing the soil structure and identifying where any compaction needs relieving.

In regards to nutrition, where manufactured fertiliser is the main source, it is worthwhile considering the use of a nitrification inhibitor to delay the transfer of ammonium N into leachable nitrate – as N uptake is prolonged in this crop and grown on light leachable soils.

West: Stephen Harrison

AICC/Southwest Agronomy (Avon)

Stephen Harrison

Stephen Harrison

Astronomical spring may have sprung but after a balmy weekend, it doesn’t feel very spring-like today. 

It’s much the same story out on farm where good progress with spring drilling has only taken place on the lighter soils.

Crop growth is patchy and apart from oilseed rape on fertile sites nothing has really roared away. Some earlier wheat is at GS30.

We are not rushing out with fungicides and plant growth regulation just yet. 

Final leaf three rarely emerges much before the end of April so we are looking at an early April T0 treatment to keep our intervals tight. 

Septoria is present on older leaves, however, there is rarely a response to controlling the disease at this stage. 

While septoria can be inoculum driven there are still countless ascospores in the atmosphere waiting to reinfect.

Treatments are more about rust and giving some cover against delayed leaf three sprays.

I have just returned from speaking at a Teagasc septoria conference where there were clear messages on the importance of varietal resistance, combinations of actives including multisites, and later drilling to help manage the disease under extreme conditions. 

Apparently, the Irish wheat area has dropped from 80,000ha to 60,000ha with one of the key drivers in the wetter areas being the fear of a complete breakdown in fungicidal control.

Mildew not a threat yet

Virtually all outstanding grass weed treatments have now been applied. Thankfully we are seeing good control where applications were made earlier in March.

Winter barley is carrying a little brown rust and mildew. The mildew is old and inactive so normal T1 treatments should take care of this. If the mildew starts to move we will include a specific treatment.

Winter oilseed rape has just started to flower. Stem extension fungicides for light leaf spot and plant growth regulation effects have now been applied. 

No, I repeat no, crops have warranted treatment for pollen beetle, as the crops move into flowering they become friends not enemies by helping pollination. The next major job will be sclerotinia at mid-flower.

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