Brown rust shows up SDHI differences in wheat
Clear differences are being observed in the ability of different SDHI fungicides to control brown rust in a disease hotspot in Kent.
In addition, the value of including a strobilurin at the T2 flag-leaf timing has been noticeable in trials run by the distribution group Zantra in south-east county where brown rust was established.
See also: SDHI fungicides essential for profitable wheat crops
Chris Bean, the group’s technical director, says the opportunity to test different T2 fungicides came when brown rust infected its Kent trial site in early May.
“Despite the fact that brown rust is a problem in most years in Kent, there hasn’t been a really good chance to look at how the SDHI range performs against the disease since they were launched.
“So this year has been quite revealing and has added to our knowledge,” he says.
Actives
- Adexar – SDHI fluxaproxad + azole epoxiconazole
- Aviator – SDHI bixafen + azole prothioconazole
- Seguris – SDHI isopyrazam + azole epoxiconazole
- Vertisan – SDHI penthiopyrad
- Imtrex – SDHI fluxaproxad
- Treoris – SDHI penthiopyrad + chlorothalonil
- Cielex – SDHI penthiopyrad + azole cyproconazole
The group’s work involved three of the newer SDHIs – Bayer’s bixafen, DuPont’s penthiopyrad and BASF’s fluxapyroxad – both as straights, where possible, and in co-formulation with other active ingredients.
On this occasion, Syngenta’s Seguris was not included.
The straights – Vertisan and Imtrex – were tested, as well as the co-formulations Adexar, Aviator, Treoris and Cielex.
“Most apparent was that Aviator was weaker on brown rust than the others, which may be due to the prothioconazole component of the product, which is recognised as being less active on rust than other azoles,” notes Mr Bean.
But without having straight bixafen to test, it is impossible to say for definite which active ingredient is letting you down, he adds.
The other SDHIs all gave very similar results and showed that with the right fungicide programme, it is possible to keep crops clean in a high-pressure season.
Of further interest is that where a strobilurin (pyraclostrobin) was included at T2, there was a significant benefit, even where the disease was established, he adds.
Some growers have had to spend more than they planned, but some applications have proved very cost effective.
“This work shows that the extra cost of £10/ha for adding a strobilurin into the programme is likely to have been a good investment this year, especially in brown rust susceptible varieties,” he says.
