Crop Watch: Sugar beet weeds and mosaic virus in wheat

The weather has swung to the other extreme and some crops, such as peas, on light land are struggling for water.

One worry for winter cereals is that those with poorly developed roots resulting from a wet spring may mean crops are less resiliant to a prolonged dry spell.

In the South West, poor patches of wheat are being seen as a result of soil-borne cereal mosaic virus and growers are being advised to consider this disease when investigating poor areas.

See also: How OSR variety choice helps crops survive flea beetle


Stephen Harrison, AICC/Southwest Agronomy (Avon)

May was a month with scarce rainfall, however, soils were well supplied with moisture from the previous monsoon and ample light levels meant winter crops have grown well. 

Spring sowings drilled into poor seed-beds, especially on heavy land, have struggled.

Timely spraying has been hindered by constant breezes and unavoidable delays to flag leaf applications necessitated an increase in dose rate.

The top three leaves remain green in wheat canopies and septoria is obvious in lower leaf layers.

Sustained dry weather has halted the progress of stem base diseases.

Grassweeds are now raising their heads above the crop.

Once again, the dominant factor in grassweed control appears to be drilling date with a delay from early to mid-October being particularly noticeable.

The new herbicide, cinmethylin, where used in a sequence, has been effective against blackgrass and ryegrass, but not where crops were drilled early into dry seed-beds. 

Wild oats

Wild oat control from contact materials has been improved this spring over last season as weeds were growing vigorously at the time of application.

One worrying trend has been the increase in poor patches of wheat as a result of soil-borne cereal mosaic virus.

The wet, “stressy” conditions in March have worsened the effects.

Please consider this disease when looking at suspect areas of wheat. The mosaic-like leaf mottling is distinctive.

On farms where the problem has been identified, the resistant variety Mayflower is being grown and is completely free of symptoms.

We need other resistant varieties; I see this as a developing problem.

Mayflower has strong resistance to foliar and stem base diseases and good grain quality.

Winter oilseed rape has finished flowering.

Crops thinned out by insect pests have branched to fill available space, and canopies are erect with good light penetration to all pod layers for yield building.

Maize on lighter soils is progressing well, but crops on heavier soils with poor seed-to-soil contact are struggling. All crop types would benefit from rainfall.


Iain Richards, Agrii (Oxfordshire)

After the wet spring, it’s no surprise that many crops have now had a month without rain.

Winter cereals over gravel are already showing clear signs of drought stress; most obviously the later drillings, where rooting was compromised by bad frost-lifting despite our mammoth February rolling efforts.

The dry weather has, however, allowed us to get our wheat T2s spot on – at full flag leaf emergence and within three weeks of our T1s.

While septoria was the main target here, our focus has, unsurprisingly, shifted towards rusts.

Thank heavens we never took our eye off this particular ball because yellow rust has really come through in the past two weeks even though it was notable for its absence at T1. And brown rust is always a threat here.

Bolstering Rylox (mefentrifluconazole + pyraclostrobin) with the most rust-active SDHI, Ceratavo (benzovindiflupyr) – as we’ve widely done at T2 – should ensure we keep both our brown and yellow rust defences up to the mark for our large Group 1 acreages of Crusoe on the one hand and Zyatt on the other.

Alongside the fusarium that is always our main T3 focus, the next question is what foliar top-up to give our standard prothioconazle/tebuconazole combination?

For yellow rust susceptible varieties, this is likely to be additional tebuconazole – or a strobilurin, where two haven’t already been used.

With deficiencies now becoming obvious, we’ll be including some foliar magnesium wherever necessary, too.

Blossom midge

Then, apart from keeping a close watch out for the dreaded blossom midge, it’s just a matter of hoping our wheats are well-enough rooted to withstand what looks set to be at least another two weeks without rain.

We have no such worries with our OSR, which continues to be promising.

It only needed a single sclerotinia spray, much of it with Mavrik (tau-fluvalinate) to deal with seed weevils.

With flowering as late as it has been, our key priority here is to keep the gate closed as long as possible before desiccation for the best pod fill and oils.

Our February-sown spring barleys are also looking very good as their first awns appear.

A robust T1 dealt with high rhynchosporium pressures well and another dose of folpet alongside a late plant growth regulator at T1.5 should have given us the best ramularia protection, leaving brown rust as our main T2 target in the coming week.

It’s the later-sown crops – maize and linseed as well as spring barley on heavier ground – we are most worried about.

Their seed-beds weren’t as good as we’d have liked and many couldn’t be rolled.

So, there’s a lot of soil type-based variation within, as well as between, fields.

We’re doing what we can to relieve obvious drought stress with foliar nutrition, but what they really need is a decent drink.


Becky Finbow, Agrovista (Norfolk/Suffolk)

Finally, we have seen some sunshine and with it a light at the end of a very long, tiring spring.

Sugar beet is growing well, with the second dose of nitrogen now applied.

Weed control has been excellent, with even some bigger weeds being taken out with a simple mix.

Unfortunately, it didn’t look like beet was going to meet in the row for the Suffolk Show, but hopefully it will catch up and maintain with the tradition of meeting between the rows for the Norfolk Show.

Aphid thresholds have been met, so crops grown from non-Cruiser treated seed have received one insecticide to provide protection from virus yellows.

Quite a few of my growers have chosen to go down the Conviso beet route this year.

Conviso is a new technology with two components: special hybrid herbicide-tolerant beet seed and ALS-inhibitor herbicides.

This combination allows growers to tackle conventional weed beet issues as well as the usual weeds.

This does lessen the number of herbicide applications, but does it give the same weed control? Watch this space.

Weeds in maize

In the East, maize is now at the three- to four-leaf stage and weeds are beginning to show.

Early drilled crops are now being recommended a herbicide containing mesotrione and nicosulfuron to tackle both grass and broad-leaved weeds.

Where blackgrass is the predominant weed, different actives – foramsulfuron, iodosulfuron and isoxadifen – are prescribed.

Although this sunshine is lovely, peas are one of the crops struggling for water, particularly on light land.

The later drilling means we are further behind than in previous years, with emergence only just apparent.

In the coming weeks, pea crops will get walked for weeds and, with limited broad-leaved weed herbicide options, either MCPB or bentazone will be recommended, depending on the weed spectrum.

For further forward crops, there are already reports of large number of pea aphids, so definitely keep an eye out.

As ears in wheat start to emerge, we look ahead to our T3 options.

Timing of an ear wash is vital to target fusarium and mycotoxins, which means spraying as soon as the ear is fully emerged, especially in unsettled conditions.

Actives such as tebuconazole, prochloraz and azoxystrobin (providing you haven’t already used two strobulurins) are best, but please consider varieties that are susceptible to brown rust, as this might require you to bolster your T3 fungicide.


Conor Campbell, Hutchinsons (Northumberland)

Thankfully, my weather prayers have finally been answered and the past couple of weeks have seen a real improvement.

The rain suddenly disappeared from the forecast and the sun came out to play.

Fields quickly began to dry out and, dare I say it, are starting to go the other way now.

I’ve been caught once or twice expressing how “a few mil at night wouldn’t go amiss for these spring crops”.

Perhaps my wife has a point – I’m never happy.

The last of the wheat T2s are on and thankfully so, I’ve had several reports from around the county of yellow rust appearing on leaf two prior to treatment and sprayer misses are terrifying to look at.

Generally, wheat crops have plenty of potential and will need looking after right up until the combine.

I appreciate the current situation, with prices for harvest having slipped back, is concerning, but our foot must be firmly pressed on the pedal for a bit more time yet.

I think the debate of “to T3 or not to T3” has been answered and I would strongly suggest treatment at ear emergence.

For those looking to push crops, the addition of a strobilurin will help maintain the green area and yield potential.

Keep septoria in mind, as I’m sure this will need keeping under control as long as possible.

Pod sealants

Oilseed rape flowering has all but come to an end. Again, the potential in these crops looks good as the pods begin to fill.

Discussions will soon turn to early pod sealants for those who can. I feel the uptake of this increases every year and the results can be seen.

Don’t be afraid to give it a go, even if you are running a trailed sprayer, as you push the tramlines down when they are still green, which helps when desiccation comes around.

Spring cereals have come through very well despite being drilled later than we would have liked.

They seem slow to get going however, as the ground begins to dry out.

Weed control is all but finished and our attention will soon turn to disease treatments.

They will soon begin to race through the growth stages, especially if soil moisture is lacking, so be mindful that sometimes going what feels like too early, will inevitably be the correct timing.

As show season approaches, I hope you all get the chance to get away from the farm and have a bit of craic.

There will be plenty of variety trials around to start the discussions for this autumn.

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