West: Grassweeds in wheat proving problematic

It has been a frustrating start or non-start to the season in the West. We start to see ground conditions drying out, think about travelling and then we have another unsettled period with rain that tests our patience.

We have managed to make a start on fertiliser applications, with winter barley, second wheats and any backward oilseed rape crops the priority. Hopefully with the forecast for a drier, more settled week we may be able to progress with more of these. The barleys have taken a yellow hue in recent weeks, so are in need of nutrient pick-me-up. Other crops of wheat and oilseed rape have also suffered, taking a blue tarnish in the recent colder weather, especially where soil is saturated. Again, these will be targeted for early fertiliser.

The lack of spraying opportunities is concerning, as we have some wheat crops with grassweeds that have kept growing all winter. Wild oats, ryegrass and brome are well tillered and becoming visible above the crop. I had hoped we would have been able to get come contact herbicide on these before the end of February, but ground conditions and colder, frosty weather has put these on hold. These will be priority actions ahead of T0.

My plans for T0 fungicide will be based around chlorothalonil, as unlike others are reporting I have not found any yellow rust to warrant inclusion of an azole or strobilurin. Although the fact that I do not have many rust susceptible varieties being grown on my farms might be a factor, however, I do have some triticale that has some active rust. Septoria levels on lower leaves are significant, but it is rainfall events in the next 4-8weeks that will determine whether we have a high disease season like 2014 or lower pressure season like 2015.

I am now a convert to a T0 fungicide on winter barley. It ensures we don’t have any disease challenges that may reduce setting grain sites and start the season with a clean crop. It will be done as cost effectively as possible, with the high levels of mildew and developing rhynchosporium the focus. Often, a low rate of morpholine fits the bill.

Another consequence of the mild autumn has been the incidence and severity of clubroot in oilseed rape, with the warm soils through the autumn being conducive for development of the disease. Last week I found another two of my client’s fields exhibiting galls. At present, both of these were only patches, but the presence alone due to its persistence in the soil means we will have to look at mitigating against it on these farms. We are successfully using resistant varieties on other farms, but we will also try to push the pH to above 7 as the disease prefers acidic conditions. Light leaf spot has started to develop on crops, so another priority for spraying is a fungicide on oilseed rape.

Where soil conditions have allowed, one or two crops of spring beans have been planted into pretty good seed-beds and spray recommendations for a pre-emergence herbicide have been sent out, as we are really reliant on residual herbicides in this crop. However, it is a challenge for this type of chemistry to keep a crop weed free for the duration of spring weed germination. So I always warn growers going back to beans or trying them for the first time not to expect a weed free crop throughout the season.

Let’s hope that the jet stream position currently bringing us colder, but drier weather stays in place to allow us to at least get started on contact herbicide strategies, as the longer they go untreated, the more costly they will be to control. If we have a month of dry weather, that might also lessen the disease pressure and we might be able to consider reducing fungicide inputs that we are all being challenged to do.

Unfortunately, we don’t have the luxury of hindsight that certain researchers have, which enables them to say at the end of the season that the most cost effective strategy was four applications of a multi-site protectant fungicide. When we make our T1 decisions in mid –April, we don’t know what rainfall for the next three weeks will be, so our strategies have to be insure against the possible weather-induced disease epidemic. We could all be much more responsive and circumspect with our strategies where needed if a reliable weather forecast for the whole season was available.

NOVEMBER
3

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