New ways to control wheat diseases, especially septoria, are urgently being investigated by Agrii.
Given the impending withdrawal of three key triazole fungicides in the next few seasons, and growing signs of septoria resistance to SDHI materials, the firm’s Syed Shah welcomed the arrival of novel chemistry in Inatreq (fenpicoxamid) and Revysol (mefentrifluconazole).
“We need new chemistry to allow us to continue to grow the crop,” he explained. “Both are quite good against triazole-resistant septoria.”
The company’s extensive replicated trials are exploring how best to use the new products in the light of the withdrawals plus further restrictions on the use of chlorothalonil.
“Epoxiconazole is likely to go in 2019, tebuconazole and cyproconazole in 2020 and probably metconazole as well by then,” explained Dr Shah. “And there are going to be more restrictions on the number of times you can use chlorothalonil and in terms of its cut-off times.”
The only triazole then remaining will be prothioconazole, and relying on that too heavily will increase the resistance pressure upon it, he warned.
“We already know there’s a shift in the sensitivity of septoria to SDHI fungicides, and if we use more SDHIs the risk of selection is going to go up. So the key question is can I reduce my reliance on SDHIs?
“Can I use an SDHI only at T2 and use good robust new chemistry at T1?”
The results and commercial implications should be keenly awaited, he believes.
When it comes to controlling yellow and brown rust the withdrawal of epoxiconazole is “quite disastrous”, according to Dr Shah. “It was a cheap way of controlling them. When it’s gone we’ll need to rely heavily on strobs, but they have to be applied early because they’re good protectants – not good curatives.”