Septoria resistance increases

NEW DATA suggests that a quarter of UK septoria isolates now carry the mutations which make them able to resist the SDHI chemistry group.

According to early season monitoring work co-funded by AHDB, 26% of all isolates gathered and tested carried an SDHI mutation. This compared to 15% and 0% of all isolates tested in a similar period during 2017 and 2016, respectively.

Collected from 22 commercial and trial sites across England, Wales and Scotland, the ADAS-led work also shows the frequency of such mutations is highly variable across the UK.

In 2018, SDHI mutation frequency ranged from 0% at one site to 48% of isolates carrying detectable mutations at another. However, isolates containing the highly SDHI-resistant C-H152R mutation were not detected at any site in 2018.

Paul Gosling, who manages AHDB’s fungicide resistance work, said: “The increase is not rapid, however, and it’s good we’ve not yet seen highly resistant septoria isolates with low fitness costs. It means the battle against SDHI resistance in septoria is far from lost and growers need to keep on with strong anti-resistance measures in their fungicide programmes.”

Experience from Ireland in 2017 showed that moderately resistant septoria isolates, at similar frequencies to those found in the UK, can be managed using robust rates of azole and a multi-site, alongside SDHIs.

Chemistry plus for linseed

Growing spring linseed as a break crop should be a little easier now that the weedkiller Avadex Excel 15G (tri-allate) can be used in winter or spring linseed as an EAMU.

One of the benefits of growing spring linseed is that it can be used to control difficult weeds, such as black-grass and brome, plus others like cleavers, chickweed, common poppy, field speedwell and red dead nettle.

“Spring linseed is expected to increase or at least remain stable this year,” according to Nigel Padbury, seeds and marketing manager for Premium Crops and the June, 2017, census put the linseed area at around 27,000 ha.

Mr Padbury said the crop had a growing outlet in the human health food sector as well as the animal feed sector. He added: “Spring linseed has one of the highest gross margins of any spring crop. At £350/tonne plus low inputs and an expected yield of 2.4 to 2.7 t/ha, its margin in 2018 is calculated to be £578/ha compared with £410 for spring oilseed rape and £445 for malting spring barley.

With sowing from the end of March through to mid-April, growers can spray off grass-weeds with glyphosate in a stale seedbed, then Avadex Excel 15G (tri-allate) can be applied pre-emergence, followed by Centurion Max (clethodim) post-emergence if required.

Avadex Granules has an EAMU for use pre-emergence in linseed and is used widely in weed control programmes to help in the control of black-grass, brome, rye-grass and wild-oats. Growers should obtain a copy of the notice of approval via the Chemicals Regulation Directorate (CRD) website.