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Crop Advice & Expertise

Three insights to improve weed control and oilseed rape disease management this October in the west

Tom Astill provides some pointers for weed and disease control in cereals and oilseed rape this October

Crop Progress

Drilling dates for oilseed rape were varied ranging from early August, even late July, into September. Early drilled crops, on the whole, look decent having been drilled into moisture and getting away from cabbage stem flea beetle attacks in the main.


Tom’s agronomy tips for October

1. Please try your best to delay drilling

Understandably after two difficult seasons for drilling winter cereals and variable spring cereal yields, growers will want to get winter wheat in the ground while soil conditions are favourable. 

Don’t forget that there are agronomic benefits from delayed drilling into the latter half of October – more time for weeds to germinate to get a stale seedbed or to help decide fields which should be destined for spring cropping.  Also, cooler and moist conditions will help extend residual herbicide activity.  Aside from weed control benefits, there is lower Septoria and barley yellow dwarf virus risk by delaying drilling.

If you have drilled early, hopefully you will have mitigated the additional threats by selecting varieties with good Septoria resistance and drilled on appropriate sites with lower grassweed pressure. Even so, where drilling earlier you will have increased grass weed pressure and you may need a stronger grassweed control programme.

2. Diversity of actives important for grassweed control

An option in wheat is Liberator (flufenacet + diflufenican) + Proclus (aclonifen). This mix is pre-emergence only and is especially strong on Italian ryegrass and black-grass, and has useful broadleaf weed control.

Proclus was introduced last season in wheat. This product brings a new mode of action to cereal weed control (HRAC 32). Aclonifen forms a film on the soil surface and is taken up by weed shoots, like diflufenican, while flufenacet is taken down through the soil profile and is mostly root acting. Having three different modes of action, Liberator + Proclus will help maximise control and reduce risk of resistance development.

Ideally apply pre-emergence sprays within 48 hours of drilling for best efficacy and pay attention to application technique. Timing is key, so if you know you won’t be able to spray pre-emergence soon after drilling then consider using a contractor.

An alternative option in wheat or barley, are the two metribuzin-containing products Octavian Met and Alternator Met (flufenacet + diflufenican + metribuzin). These can be used at the full rate of 1.0L/Ha up to the end of September, then can only be used at 0.5L/Ha until the end of November. 0.5L/Ha delivers 120g flufenacet so it is useful pre-emergence for annual meadow grass and broadleaf weed situations or could it be applied as a residual top-up early post-emergence. Metribuzin will give some contact activity on small weeds.

3. Use SpotCheck to assess oilseed rape disease risk

Phoma pressure as we approach the end of September has been low so far, as it has been reasonably dry through August and September. The risk to bigger crops will be less as it takes more time for the leaf infection to make its way into the stem where it can develop stem cankers. Light leaf spot risk might be higher again this season as earlier drilling will favour it.

Our SpotCheck service will be running again from 1 October, which is a great tool for checking whether your crops have any of the oilseed rape diseases, but particularly light leaf spot which is not the easiest to identify.

If you would like to send in a sample, go to our website to register for a sample pack.

Thresholds for Phoma risk, as well as varietal resistance and SpotCheck samples for light leaf spot symptoms can all help decide whether a spray is needed. If you do need to spray for either Phoma or light leaf spot Aviator (prothiconazole + bixafen) at 0.5-0.75 L/ha is a good option for both diseases.


Register for the Seminis Brassica Innovation days

The Seminis Brassica Innovation days will be held on 13 and 14 October, just west of Boston. This is a bit of trek from the west, but there will be plenty to see and talk about – including varieties as well as fungicide and insecticide plots. If interested, please click this link for more information and to register.

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