Protecting cereal crops is becoming increasingly complex, delegates attending the AHDB Agronomists’ conference heard.
The efficacy of SHDIs on septoria appears to have stabilised in the 2018/19 season following several years of concern over its decline.
Presenting data on fungicide efficacy at the AHDB Agronomists’ Conference, Dr Jonathan Blake said: “In 2015 we were getting 90 per cent control from full or half label rate. In the last two years this has been closer to 60 per cent but there has not been a huge further shift over last year.
“In 2019 we have also not seen further evolution of azole resistance.”
Dr Blake said fungicides had been tested in a primarily protectant situation this year as April and May had been dry and most rain fell in June after they had been applied.
The results included data for Revystar XE (mefentrifluconazole + fluxapyroxad), the new triazole/SDHI fungicide for cereals. Dr Blake said: “It is very effective, with a yield response up to full dose. This is 0.3 tonnes/hectare compared to the next nearest treatment.
“AscraXpro was ahead of Elatus Era in septoria control in 2019 – they are separating a bit. In solo trials, SDHI Imtrex offered 60 per cent protectant control and prothioconazole, 45 per cent – this is not changing significantly.”
Elatus Era (benzovindiflupyr + prothioconazole) gave the highest yield response on yellow rust and was matched by Revystar XE on brown rust.
For rhynchosporium and net blotch in barley, fluxapyroxad or prothioconazole based products lead, said Dr Blake. “The main change in net-blotch is the dose rate at which we see good control – Imtrex, Proline and Comet mixtures used to be good at half label rate but now we are needing to apply more.”
Loss of chlorothalonil next May will have an impact on ramularia control. Prothioconazole offers some activity and Revystar XE looks promising, however, cost of the latter may be a barrier to its use, suggested Dr Blake.