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Crop Advice & Expertise

Three tips for agronomic actions in East Anglian crops this October

James Wilkins highlights three key areas for attention in October

Crop Progress

Parts of East Anglia have caught considerable downpours in September, while others may not have had very much rain at all. That was after what has been summed up as the wettest, driest August.

Quite a bit of oilseed rape was drilled in late July and early August when there was good soil moisture, and some of that has come through and looks quite good. There are other bits that went in from mid-August onwards, which didn’t have any significant rain on top until just recently and that’s more variable and patchier. Time will tell how successful that will be.

I haven’t heard of any crops being written off as we approach the end of September, but it might be a matter of time with a lot of the emergence in the last couple of weeks coinciding with the migration of cabbage stem flea beetles. With slow growing conditions that hasn’t been the best timing.

Early wheat drilling started in mid-September, where they didn’t catch high rain, but at the moment it is in the minority. That said, with two difficult autumns in a row, there is definitely an eagerness to get going.

 

James’ agronomy tips for October

1. Know your weed enemy

For those drilling in October, the starting point is knowing your enemy. There is an increasing threat of ryegrass around East Anglia, but the dominant grassweeds are still black-grass and annual meadow grass.

Black-grass is predominantly an autumn germinating species so delaying drilling so you can control outside of the crop is as important as anything you can do in the autumn. Obviously there is a flipside that if it comes very wet it can be difficult to get a good seedbed.

That’s also a bit of a trade-off for residual herbicides, as it helps to have a firm, fine seedbed that can take a layer of residual herbicide on the soil surface, and also a bit of moisture for best efficacy.

You’re ideally looking to drill up to a point where you know you can roll and then spray within 48 hours – that’s particularly important in difficult black-grass situations where we know the pre-emergence applications generally lead to better efficacy.

Rolling before spraying is the better order when using a mix such as Liberator (flufenacet + diflufenican) + Proclus (aclonifen) as you don’t want to be breaking up the aclonifen layer in the soil surface after application.

Drill to a depth of 32mm to help minimise any chance of crop safety issues. A grower trial last season, where there was a high rainfall following drilling highlighted the difference between Liberator + Proclus and a flufenacet + pendimethalin plus diflufenican mix in crop safety. Two to three weeks after drilling, there was 38% improvement in emergence for the side of the trial treated with Liberator + Proclus.

Liberator + Proclus gives a good level of control of both black-grass and ryegrass, but it is worthwhile considering the rest of the programme. The addition of triallate either as a liquid or in sequence as granules can help boost black-grass efficacy, while where ryegrass is more of a concern then prosulfocarb might be the choice.

Using aclonifen and metribuzin (see below) in programmes brings different modes of action and takes the pressure away from flufenacet, prosulfocarb and triallate which are all in the same mode of action group.

 Tramline trial comparing establishment of wheat treated with flufenacet + pendimethalin + diflufenican on left and Liberator + Proclus on the right.

 

2. Consider metribuzin products for top ups and for annual meadow grass

Where a top up to residual herbicides is required, usually within about six weeks, in moderate to high grassweed populations, our metribuzin-containing products Octavian Met and Alternator Met (flufenacet + diflufenican + metribuzin) are good options. They will top up flufenacet levels, while metribuzin is both shoot and root uptake, so is quite a useful addition at that post-emergence timing

From 1 October to end of November the maximum dose of Alternator Met and Octavian Met is 0.5 L/ha.

It’s also a very useful as either a pre-emergence or early post-emergence option for growers with annual meadow grass and broadleaf weed populations. Weeds such as groundsel and cranesbill are increasingly challenging to control in the spring with contact herbicides, which metribuzin is more than useful against.

 

3. Use SpotCheck to assess disease risk in oilseed rape

A warmer, milder and wetter autumn last year meant light leaf spot came into crops four weeks earlier than the previous season at the back end of October / early November. That was signalled by our free SpotCheck service, which enables you to get oilseed rape leaves checked for light leaf spot and other oilseed rape diseases by the experts at ADAS, and provides a good early warning system.

SpotCheck will be running again this season from 1 October, and you can register for a sample pack on our website at cropscience.bayer.co.uk/bayer-spotcheck. It helps clarify whether you have light leaf spot, which can be difficult to identify in the field and the severity of infection.

The sensitivity of light leaf spot to azole fungicides is slowly reducing, according to research, which further justifies the use of products with another mode of action, such as Aviator (bixafen + prothioconazole). It has activity on both light leaf spot and Phoma, and the formulation benefit of being rainfast in minutes is useful especially in a catchy autumn.   

Phoma risk is likely to be highest in smaller crops, especially in ones without good varietal resistance as the fungus has less far to travel to get into the stem. The general threshold for phoma application is when 10-20% of plants are affected.

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