West: Autumn weather arrives to heighten OSR disease threat

After weeks of following my postman’s lead by keeping the shorts on due to the warm and dry weather, autumn has arrived and it is regrettably back to wellies and waterproofs. I suppose with the driest September – only 12mm recorded in my gauge – for a long time then we should have expected it, nevertheless, it comes as a timely reminder that autumn is upon us with 54 mm this week.

Early planted cereals have established well despite the dry September conditions, but surprisingly the slugs have still been an issue in some wheat after oilseed rape. Generally these crops have grown away well and are now at 3-leaf with first tillers emerging.

Gout fly eggs are common in these crops, but only on 10-25% of tillers, so below threshold and with most Deter (clothianidin) treated I will hold off with an insecticide, as gout fly do not move between tillers, so will rely on tillering to compensate.

Flufenacet herbicides have been prioritised to fields where brome, ryegrass and occasional blackgrass are the dominant weeds. Barleys have also been prioritised due to the lack of post-emergence  grassweed herbicide options.

Oilseed rape crops have got away well with enough moisture below a dry surface for good emergence. For us, the cabbage stem flea beetle (CSFB) storm never really happened (apologies to those who have suffered losses). After my vigilant checking at emergence, I was surprised how little damage I found and with plants growing rapidly, they soon grew out of the high risk phase. Yellow water traps put out to monitor CSFB numbers yielded very few beetles, but plenty of flies!

It was noticeable how many turnip saw flies were caught, from which we are now starting to see larvae in crops and is a first time I have experienced this pest in the west. Quite a few of these crops are getting large, according to the Green Area Index (GAI) app of 1.5-2.0 GAI, in which I am also finding aphids, so will probably get one of the insecticides with a new autumn approval that should also get incidental control of turnip saw fly larvae.

Phoma lesions are just starting to develop, although below threshold at present. Recent rainfall is likely to cause further spread, so fungicide strategies are now on the agenda.

The loss of flusilazole is a blow, as the alternatives are a step up in price at a time when oilseed rape is a marginally profitable crop at current prices. Whether to opt for a single spray programme, choosing a product based on the need for a plant growth regulator (PGR) and variety disease rating is dominating decision-making. Gone are days of a programmed approach to growing OSR and back to good agronomy skills of identifying weed, pest and diseases and treating appropriately if reach economic thresholds.

Current prices are causing a refocus on being economic with strategies, although it is a constant cause of frustration that not all growers know how much it costs them to produce a tonne of crop, especially averaged across a number of years. So I am pleased that HGCA are supporting the Monitor Farm programme, which gives growers the chance to collaborate and share best practice by benchmarking themselves with other local farm businesses. I look forward to joining others for some lively discussion on mixed farming prospects at the Hereford monitor farm on 12 November.

Let’s hope we have a bit of settled weather now to get any outstanding spraying completed on second and later planted wheats, along with disease control on oilseed rape, before soils get to wet to travel, but having just seen the forecast for the week ahead it doesn’t look too hopeful.

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