Published on 30th October 2023
Four agronomy tips for growers in the west
Gareth Bubb takes a look at autumn weed and disease control in November for growers in the west
Storm Babet brought flooding to parts of the west, which brought a halt to fieldwork. Fortunately, I think about 80% of drilling was complete, with mostly land following maize and potatoes left to drill.
Not all wheat crops will have received a pre-emergence herbicide, however, as understandably it is quite often the mindset to get it drilled and then let the agronomist worry about any problems if you don’t manage to get it sprayed.
Gareth’s agronomy tips for November
1. Weed control options for November drilled wheat
Assuming weather comes good to allow more drilling, the inherent weed burden in November drilled wheat should be lower. However, it is still worth doing something as we know herbicides applied pre-emergence generally have more efficacy, especially on some of the more difficult weeds, with perhaps bromes being the only exception.
There are three possible Bayer options: the starting point is Liberator (flufenacet + diflufenican). Adding in Proclus (aclonifen) should give you longer lasting activity, while there are also the metribuzin-containing products, Alternator Met and Octavian Met (flufenacet + diflufenican + metribuzin).
The latter are particularly good options where you’re worried about the crop coming through as Proclus is pre-emergence only, whereas the metribuzin products can be used post-emergence as well.
2. Weed control options for October drilled wheat
Where pre-emergence treatments were applied, it’s important to understand the relative length of time the residuals will last for. Diflufenican and aclonifen will last longer than flufenacet or prosulfocarb elements.
You will likely need to top up the residual, assuming you’re able to travel with the sprayer, and if you’re concerned about barley yellow dwarf virus, there’s a good chance when you do the T-Sum calculations that applying the herbicide will coincide with the insecticide.
Keep mixing different modes of action through the programme, especially when trying to control difficult Italian ryegrass. Again the starting point is probably Liberator or the metribuzin products and you can consider adding pendimethalin as a different mode of action.
An alternative strategy if the weeds are getting beyond a couple of leaves, which is more likely if you haven’t been able to apply a residual up until now, is to use a contact-acting product, such as Atlantis OD (mesosulfuron + iodosulfuron). I’d still add a residual, such as Liberator, at this time of year.
If it is an annual meadowgrass plus broadleaf weeds type situation, Othello (mesosulfuron + iodosulfuron + diflufenican) is a good choice.
3. Is it worth applying an autumn OSR fungicide?
As ever there is a broad range of oilseed rape crops in the west from the very good to the failed and redrilled, and others that growers are still making up their minds on.
I’ve heard of quite a few reports of Phoma in crops, which is no surprise given there is a direct correlation with rainfall. It’s more of a problem in smaller crops where is less distance for infection to travel to get into petioles and ultimately cause stem cankers.
November is when you might also start to see light leaf spot, and if you are spraying it’s important to use a product that has activity against both diseases – not all of them do.
4. When to terminate cover crops?
There are a lot of variables to consider when thinking about cover crop termination – what are you trying to achieve, avoiding bare soil but allowing soils to dry out before planting a spring crop, using glyphosate, grazing, or rolling on a frost, etc.
Everybody has different ideas but if you are using glyphosate it’s important to use the right product at the right dose to control the cover crop species and any weeds.
There is good advice on our website about how many grammes to control different species – some are more difficult to control than others. Using the right formulation is also important – better formulations will give a better kill.