This month’s update includes information on:
Oilseed rape has generally established well and is now ahead of flea beetle damage. Size of plants varies from 4-8 true leaves, depending on drilling date. First signs of Phoma are appearing in forward crops and this will need monitoring with a view to treatment when 10% of plants are affected.
It is sensible to use a product with both Phoma and light leaf spot activity, as infection of the latter disease may have already occurred. In addition, it might not be possible to get back in with a second spray in November, so you will at least have some insurance against light leaf spot.
Monitor crops for grassweeds such as black-grass and treat emerging plants early – no more than 2-3 leaves – for best control. Later germinating grassweeds can be controlled with applications of carbetamide or propyzamide when soil temperatures drop.
Drilling of winter cereals has started, but mostly on lighter land where black-grass is not an issue. These crops have gone into good, moist seedbeds and should grow away well. Winter barley drilling has also begun on heavier land, although seedbed conditions in a lot of cases are less than ideal for pre-emergence herbicide application, with variable seed depth. This could be an issue due to a lack of post-emergence contact herbicide options. Where possible, apply the planned pre-emergence when the crop reaches one true leaf. Control will be compromised, but it’s better to get something on than nothing.
Drilling of wheat on black-grass land hadn’t started at the end of last week, but there will be some moving now. The intention seems to be to wait until mid-October before starting to drill, allowing further flushes of black-grass to come through. We have already seen some big flushes so far, which leads me to disagree with claims from that black-grass seed shed this autumn will have high dormancy.
The main concern with growers seems to be that with current wet soil conditions and the danger that holding off drilling until mid-October may result in no drilling being done at all.
Pre-emergence product choice will be vital this autumn as there may only be one chance to get on fields before weather conditions close in. Correct choice and good, timely application may well make or break grassweed control programmes and subsequent success of the crop. Liberator (flufenacet + diflufenican), Movon or Vigon (both flufenacet + diflufenican + flurtamone) plus 2L/ha of Defy (prosulfocarb) pre-emergence have performed well here over the last couple of years, while following up with Avadex granules (tri-allate) certainly improves grassweed control.
There is also concern about slugs, with large numbers of small grey field slugs present in many soils. Close monitoring of this situation and appropriate treatment where necessary will be needed as the season progresses.