Winter wheat growers will welcome the launch of InatreqTM last week by Corteva, knowing that it will be available here this season.
This new active is confined to use on winter wheat at present, but it is expected that it will be cleared for use on other crops in time. Its introduction follows that of Revysol last season and both of these come at a time when there are signs of weakening in the SDHIs.
While only cleared for use on winter wheat and durum wheat for now, it is still a very useful addition as it controls the two major diseases, septoria and yellow rust. It is from a new family of fungicides – the picolinamides – and brings with it a new mode of action. It is to be marketed here by Terrachem as the standalone products Questar and Peacoq, and as a co-pack with metconazole called Aquino plus Turret.
Inatreq is a trademark for the active fenpicoxamid. It is particularly strong on septoria and yellow rust. Its mode of action is unique in cereal fungicides and is described as a quinone inside inhibitor, or QiI.
Like many other actives, it inhibits respiration in the mitochondrion of the fungal cell and causes it to run out of energy and die. Its site of action is at the inside of Complex 111. So far, it shows no cross-resistance to existing cereal fungicide chemistries.
A crossover active
The active is produced in nature as a natural secretion from a streptomyces bacterium. This excretion is code-named UK-2A, which is the actual fungicidal active.
However, in its natural state, UK-2A will be broken down by light, so it would not seem well suited to field application. The active is also quite immobile, which would be a serious limitation to its ability to protect crop leaves.
This technology provided the active with huge external movement capability on the plant tissue, meaning it does not need to move internally to provide cover
Both of these challenges were overcome by Corteva’s formulation chemists. The photosensitivity was fixed by adding a tail to the molecule and this new molecule converts back to UK-2A inside the plant tissue or in the fungus.
The lack of mobility was tackled using a new formulation technology called i-Q4, which gave huge spread capacity to spray droplets to enable them to run all over the leaf and up on to adjoining or emerging leaves post-application.
This technology provided the active with huge external movement capability on the plant tissue, meaning it does not need to move internally to provide cover. While other products have had external movement in the past, this seems like the first well-proven example of this type of distribution.
Because it is a single site active, it is vulnerable to resistance development. While it is being sold as a standalone active, it must never be used alone in practice and should have at least one other active partner, plus a multisite.
To help against resistance risk, its use is confined to a single application per crop at either the T1 or T2 timing.
While it has a 2.0l/ha maximum use rate, it is envisaged that 1.25l/ha will suffice for the control of yellow rust
As rate is also considered as a driver for resistance development, its high inherent activity is being used to minimise the rate of active needed. Corteva says to use the minimum rate needed for the job.
While it has a 2.0l/ha maximum use rate, it is envisaged that 1.25l/ha will suffice for the control of yellow rust, with up to 1.5l/ha recommended for septoria control in conjunction with a tank-mix partner.
Longevity is key
Researchers said that Inatreq-treated plots looked similar to other good treatments for the first month or so, and it is only after that when the product shows the longevity of its activity. As a result, many of the observations to assess it are taken at around 50 days post-treatment, rather than 30 days. It is not clear whether this longevity is a result of its slow degradation within the plant, or if it is a result of the surface distribution providing good overall coverage and a continuous drip feed to help slow disease development.
While septoria and yellow rust are its main disease strengths, it also has very useful activity on other diseases, especially when used with tank-mix partners like prothioconazole. These include brown rust, fusarium ear blight, tan spot, powdery mildew and eyespot.
Trial results presented at the launch showed variable yield benefits from the use of Inatreq versus alternative chemistry.
On balance, the average yield benefit seemed to be between 0.6 and 0.8t/ha and even more in high septoria pressure situations.