OSR losses to cabbage stem flea beetle in the north, the arrival of a new blackgrass herbicide for wheat and the barley yellow dwarf virus risk in cereals are among the topics being discussed by this week’s four agronomists.

See also: How stewardship is helping estate to form future plans

East

Marcus Mann

Frontier (Essex)

While the hot dry summer allowed harvest to be completed earlier than I can remember, the impact of the dry conditions since February and the ongoing soil moisture deficit is now creating its own set of challenges with regards seed-bed preparation, particularly on the heavier soils.

That said, the limited rainfall we have received in the east has made all the difference, and where crops have been drilled, they have gone in remarkably well.

Consolidating seed-beds as soon as possible after drilling is imperative to conserve what moisture is present and to help optimise the efficacy of the pre-emergence herbicides.

With soil temperature still relatively warm, crops are germinating rapidly, unfortunately along with the blackgrass and ryegrass. 

One of the downsides of the dry conditions post-harvest has been the lack of grassweed germination and the opportunity to create stale seed-beds.

On the worst fields, sitting tight and allowing fields to green up will pay dividends in the long run.

The benefits of later drilling are well understood, but the value of a fully integrated approach should never be undervalued.

New for this autumn we have Luximo (cinmethylin) which will be incorporated alongside existing active ingredients as part of the residual stack. In trials over the last three-to-four years we have seen tangible benefits from including the new chemistry within the programme. 

Ryegrass is becoming a bigger problem nationally and with resistance increasing to a range of actives including flufenacet, cinmethylin is a very welcome new option.

If conditions remain dry, with sporadic grassweed germination, it will be important to monitor grassweed pressure with peri/post-emergence top-ups potentially being required.

Cereal pests

Aphids are being spotted on emerging cereals and must be carefully monitored.

With current milder than usual temperatures they will reach T-Sum-170 (170 day degrees above a threshold of 3C have accumulated from crop emergence) quicker and repopulate into the secondary generation which will spread the virus.

OSR continues to disappear in the east with a small viable area remaining. Fortunately, mild weather is enabling growth, but decisions have been quickly made on small sparse crops that will likely cause greater long-term issues for grassweeds if left to harvest.

There are reports of beet moth larvae are being found within sugar beet crops. Although nothing can be done to existing larvae, it will be worth noting crops that have visible populations so that the crop residue is ploughed once the beet are lifted.

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West

Gavin Burrough

Pearce Seeds (Dorset, Hampshire and Wiltshire)

Oilseed rape crops are a mixed bag, some of the early drilled crops are now well away to the point of wondering if a plant growth regulator will be required.

This is a relief considering at the time of drilling conditions were a tad dry. Some of the later drilled crops are struggling and are thin.

I have not used any pre-emergence herbicides again this year on OSR, and some fields are surprisingly clean of broad-leaved weeds.

Others will be treated with either Belkar (halauxifen + picloram) now or Astrokerb (propyzamide + aminopyralid) later in the year when soil temperatures are cold enough depending on the weed spectrum present. 

Volunteer cereals were, however, very quick to appear and needed controlling with a graminicide as soon as the OSR was big enough and we were brave enough to think that the crop had established.

Currently crops are generally free of disease, but they will be monitored and treated as and when necessary.  

Greening up

The September rains have transformed grass fields which four-to-six weeks ago were various shades of brown. Thankfully they have greened up again to what they should look like.

The early maize harvest has allowed a lot of short and longer-term grass seed to be drilled in to maize stubbles which will not only help produce some much-needed forage next spring, but also provide some good ground cover for the winter to help reduce soil erosion as no doubt one day it will start raining, a lot. 

Winter cereal drilling is progressing well, fields which are burdened with bad grassweed problems have only just started to be drilled at the time of writing.

The weather forecast is starting to look more unsettled, so on a positive note, this will hopefully, help any pre-emergence herbicides which have been applied to work more effectively.

Earlier drilled fields where annual meadow grass is the main concern will have had or soon have a pre- or early post-emergence herbicide applied, normally containing picolinafen and pendimethalin.

There will be regular monitoring for aphids during the current warmer weather. I am sure it will not be long before they are found. 

Winter oat drilling has begun with herbicide Liberator (flufenacet + diflufenican) being applied under an extension of authorisation for minor use. 

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North

Patrick Stephenson

AICC (Yorkshire)

An almost perfect harvest period has now given way to a perfect drilling period, and in my part of the world the only areas left to drill are following potatoes, maize, and beet.

Seed-beds have been excellent, and overall things have gone well. This may sound like paradise, but sadly not so.

Having had a year’s respite from cabbage stem flea beetle, this year the pest was back and having a ball.

The saying is “Idle hands do the Devil’s work” and unfortunately with an early finish to harvest, we made the decision to increase the OSR area and drill many fields due for second wheat with the crop.

Unfortunately, not one has survived the onslaught of flea beetle, so back to plan A. In terms of the total drilled area, this will amount to between 15-20% lost.

I am now up to theory 500 on how to manage flea beetle.

I feel there are a multiple small advantages to be gained from long stubble, nitrogen, lucky charms, and companion crops, but all these pale into insignificance compared with a good drop of rain.

On a positive note, weeds have also been slow to grow, meaning we have been able to wait and use the contact materials once the crop has established.

The forward crops have now had sufficient wet periods for there to be a theoretical risk from phoma.

I still have found no lesions and many of the varieties planted have resistance ratings of 6 and above. As the weeks tick by the need for an autumn fungicide diminishes quickly.

Wheat

The early drilled wheats are now starting to tiller and the weekly inspection for aphids is in full swing.

Many growers do not now want to use an insecticide and justifying the use is difficult. The last bad year for barley yellow dwarf virus was 2011, even then timing was critical for good control.

The north is generally a low-risk region, however, if the autumn is mild and open aphids will thrive, so monitoring is important.

Pre-emergence sprays have been applied and, hopefully, there has been enough moisture to ensure good efficacy.

Top-up post emergence applications are now under way; these vary depending on the weed spectrum and what pre-emergence was used.

The big plans to use a large amount of cinmethylin (Luximo) evaporated, as drilling started in near desert-like conditions.

I have used the product, and, in some cases, it will be the follow-up to a flufenacet based pre-emergence. The success of the new chemistry will be judged by its infield performance.

Winter barley remains our Cinderella crop – a useful rotational tool in the north, to spread harvest and open drill timings for the following OSR crop.

The problem is that profitability is marginal, grassweed control in the crop is challenging, and it loves turning yellow all winter!

Cultural techniques are, in my opinion, the best way for my growers to tackle the problems we have with weed resistance.

This inevitably leads to rotational changes, and we introduce spring crops, beans, rye, oats, and grass.

The rotation has now become more complex and flexible, but we are having success in managing difficult weeds.

Beans are now being drilled and pre-emergence weed control is vital to ensure a partially clean crop.

If I was to offer my clients a re-run of harvest 2022 and autumn drilling 2022, next year they would bite my hand off!

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South

Oliver Bennetts

Zantra (Kent)

As we move into autumn, the South East remains relatively dry. The hottest and driest summer for years led to an early and quick harvest, but has left soils like concrete.

Rain in September has allowed cultivations to happen, but wasn’t enough to tempt everyone into drilling rape. However, some went in during late September, continuing into early October. Establishment of earlier drilled crops has been a little patchy due to dry soils, but they are growing away, so far relatively untroubled, by flea beetles.  

Wheat drilling in the area is just about in full swing, with the dry weather over the past few weeks leading to few interruptions.

Warm weather and soils are encouraging rapid crop emergence. This means  there is a risk of aphids carrying barley yellow dwarf virus infecting these crops. Colleagues are already reporting aphids moving from volunteers to newly emerging cereals despite stale seed-beds being used to help control grassweeds.

Aphid trapping is also showing that potential BYDV aphid vectors are already on the wing. I’m using the BYDV T-sum calculation app to predict when the first aphicides will need to be applied. From past years, this usually seems to coincide with the crop reaching the 2 to 3 leaf stage!

The app seems to come more into its own when deciding whether follow-up treatment is needed.

Bean drilling

Field preparation is going on for winter beans which are normally the final crop to be drilled. The correct cultivations are key to make sure of a good seed-bed for pre-emergence weed control and to ensure that the root system of the bean can develop to depth unimpeded by compaction – which beans absolutely loathe.

As we move through the autumn, spray days become fewer, and workload mounts up. To repeat what I said last year: for the most effective pre-emergence weed control, keep sprayer forward speeds to around 12kph, boom height to about 50cm above the soil, use alternating backward and forward facing nozzles and spray at 200 litres/ha of water.

Herbicides are expensive and under pressure – they need using carefully to optimise performance.