South: Hoping for an “open” autumn

With moisture now returned to top layers of soils, oilseed rape is continuing to establish. Most crops now have at least one or two true leaves, some more and some just emerging. Hopefully the autumn will stay “open” and so crops keep growing. Most crops have received some nitrogen, so as long as the weather is warm they will be able to use it, which will increase winter survival (assuming that we get a winter).

The two photos show the difference between this year and last quite clearly. Both were taken on 26 September and both plots drilled with the same machine (Simba DTX) at 50 seeds per sq metre. Drilling date was very similar, 1 September 2011 and 3 September 2012. The left hand one is from 2011 and the rows are clearly visible and plants have 3 leaves (all a good size). The right is this year – plants are there, but much smaller.  In some places the rows are just visible, often not. Leaves are far smaller at the moment.


Generally slug damage at the moment is less than expected, but crops are still small enough for slugs to do damage very quickly if not controlled. However, there are places where the slug burden has been huge and have now had four applications of pellets. Don’t be tempted to keep re-applying metaldhyde as you will use more than 210gms ai between August and December. My preferred alternative is Derrex (ferric phosphate), which has managed to survive in excess of 40mm of rain in 24 hours. Regular checking is vital, as is re-pelleting if needed.

Volunteer cereals and blackgrass are emerging rapidly. With OSR plants being much smaller than normal, don’t let the volunteers get big before taking them out, otherwise they will soon be affecting the crop. The last thing we want to do is stress a small crop in late autumn so take out the volunteers, even if it means using two graminicides this year. In areas where blackgrass is a major problem I’ll be using the Crawler (carbetamide) followed by propyzamide option, as long as the crop is large enough to cope.

Phoma risk is now very high. It was visible in volunteer OSR on stubble fields in early September, but at the time of writing (30 Sept) I haven’t seen any in crops. That is likely to change in the next week. The threshold for treatment is 10% of plants. With crops being so small this year it will only take a few days for lesions to grow down to plant stems, so don’t delay application of Capitan (flusilazole). If going in with a graminicide, there is a case for combining that with the first phoma spray to give protection as well as saving a sprayer pass.

At the moment there is no need for anything that has a growth regulatory effect, but depending on the weather that could change.

At the moment there have been very few cereals drilled, due to ground conditions and the weather.  Even though blackgrass dormancy levels are high this year, where soil has been moved there is good germination, so don’t miss the opportunity to stale seed bed with glyphosate.  At this time of year cultivations won’t kill blackgrass unless it’s very good ploughing. 

Every week that drilling is delayed will reduce the risk of BYDV infection for autumn cereals, but remember that the green bridge increases risk so the glyphosate application will benefit here as well.  Aphid numbers are not quite as high as last year but more aphids are likely to be carrying infection and there hasn’t been significant frost to kill them, so crop risk is as high as last year.  If we get a similar weather pattern to last year then more insecticides will be needed.

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