Grower turns to new flag-leaf fungicide to fight resistance
Julian Gibbons © MAG/David Jones Julian Gibbons is trying out a new type of flag-leaf fungicide on his winter wheat to reduce the risk of septoria building up resistance to fungicide sprays on his Hampshire farm.
He has already moved to more disease-resistant wheat varieties and now uses a fungicide with a different site of action to give good disease control and help protect the efficacy of existing SDHI and azole fungicides.
See also: Long-awaited wheat fungicide approved for this season
For this spring, he is planning to use the new product Univoq on his more disease-prone milling wheats to bring in this new chemistry after the banning of some key fungicides that now makes disease control more difficult.
“Septoria drives everything for us. We have 900mm of annual rainfall, and yellow rust is not as issue, so it seem sensible not to put more pressure on fungicide programmes for septoria control,” Mr Gibbons says.
Farm facts
M Gibbons and Sons, Upper Farm, Bradley, Alresford, Hampshire
- Soils silty loams to silty clay loams
- Area 660ha of arable
- Cropping Winter wheat, winter barley, spring barley, winter oats, peas and spring beans
Milling wheat
That means he will use Univoq on half his Crusoe milling wheat at the key T2 flag leaf stage, and the other half will be treated with another fungicide newcomer, Revystar.
Univoq, only approved for use in late March, contains fenpicoxamid (also known as Inatreq) plus the widely used azole prothioconazole, and is marketed by Corteva Agriscience, while BASF’s Revystar contains its new azole mefentrifluconazole plus its existing SDHI fluxapyroxad.
Fenpicoxamid comes from the picolinamide chemical family, which has not been used before on cereals and has a different site of action to control disease fungi than SDHIs and azoles, so it could be a big step forward in slowing down disease resistance to fungicides.
“We are using Univoq predominantly because it is not an SDHI. As a non-SDHI, it will take the pressure off SDHIs,” he says.
Variety choice
Mr Gibbons, farming in partnership with his brother, Andrew, grows 224ha of winter wheat on his 660ha arable operation at Upper Farm, Bradley, a few miles south of Basingstoke.
Crusoe makes up about one-third of his wheat, and the rest largely Graham, with some Extase and Basset.
Julian Gibbons’ Crusoe wheat crop © MAG/David Jones
His first move to counter fungicide resistance has been to move to varieties with better disease resistance to limit fungicide use.
Therefore, he is using the more disease-resistant Graham and Extase, while Basset is in decline, and Lili and Diego have disappeared from the farm.
He has found no obvious replacement for his old milling favourite, Crusoe, and the variety does well consistently. Its Achilles heel of brown rust is not a great issue on the farm as the disease is rarely a problem.
Crusoe yields on average 9.5t/ha and generally gives a good milling sample on Mr Gibbons’ silty clay loam soils, while Graham and Basset yield more than 10t/ha, with Extase new to the farm this season.
Fungicide products
- Univoq Picolinamide fenpicoxamid (Inatreq) + azole prothioconazole
- Revystar SDHI fluxapyroxad + azole mefentrifluconazole (Revysol)
- Aviator SDHI bixafen + azole prothioconazole
- Ascra SDHIs bixafen and fluopyram + azole prothioconazole
Four-year trial
His second move is to use as wide a variety of fungicide types as possible to counter septoria, and he has been trialling an Inatreq/prothioconazole mix for the past four years with Corteva on 1ha strips on the farm.
He saw no difference in yield between it and any competitor SDHI/azole product over those four years, using them on Crusoe for two seasons and Basset for the other two.
Mr Gibbons says the past few years have presented low septoria infection rates, but there is always the fear of a wet spring and the disease causing a real headache.
Therefore, he is keen to mix chemistries to keep fungicides effective.
This year, he has switched to a three-spray policy, leaving out an early T0 spray because of the very dry spring and the ban on chlorothalonil, which was commonly used as a protectant against septoria at this early stage.
Flag leaf emerging on Extase © MAG/David Jones
Loss of fungicides
The multisite chlorothalonil was banned last May, while the popular azole epoxiconazole is in a use-up period this season before a full ban takes effect. This loss of chlorothalonil has led Mr Gibbons to look at using the most effective fungicides.
With the absence of a T0 this spring, his T1 was a stronger fungicide than he has used in the past, when Tracker (boscalid + epoxiconazole) was chosen. Boscalid was the first SDHI introduced back in 2003.
Mr Gibbons’ Crusoe wheat is more disease prone and, as a milling wheat, is more valuable than other varieties, so his T1 across his 74ha of the variety was Ascra (bixafen and fluopyram + prothioconazole).
For his Graham and Extase, he used the less-expensive Aviator (bixafen + prothioconazole), while the Graham had some tebuconazole added due to worries about yellow rust with the variety.
Flag-leaf sprays
The T2 flag-leaf application plan is for Ascra on the Graham and Extase, and then the newer products Univoq and Revystar on the more disease-susceptible Crusoe. Mr Gibbons says these two have the best kick-back or curative activity on septoria.
For the T3 ear spray, the Crusoe will likely get an azole mix of prothioconazole/tebuconazole, and possibly a strobilurin if the disease pressure is high. The other varieties will see just tebuconazole or perhaps a tebuconazole/prothioconazole mix, depending on disease.
His programme is aimed at spending £90/ha on the Crusoe and £60-£70/ha on the Extase, and if the latter does well, he will look to increase its area in the future.
“The disease-resistance risk is making us look more closely at variety choice and the use of a mix of fungicides,” he adds.
Third systemic group will help counter septoria threat
The new fungicide Univoq will lower the risk of disease resistance developing by offering a third group of systemic fungicides to control septoria in wheat.
Most systemic control of this disease relies on just SDHIs and azoles, so the launch of a new product with a different site of action could help slow down the decline in efficacy of SDHIs and azoles.
Univoq from Corteva, launched this spring, is the first new systemic group of chemicals used for septoria since the first SDHI, boscalid, was launched in 2003, and comes after another fungicide newcomer, Revystar from BASF, was introduced in 2020.
Univoq has been assessed as being as effective on septoria as Revystar, according to independent AHDB trials, slightly better than Revystar on yellow rust and slightly below Revystar’s level of brown rust control.
Site of action
The efficacy of SDHIs and azoles against septoria has been slowly declining over recent years, so the launch of new chemistry with a different site of action is significant to help prevent the build-up of disease resistance.
Mike Ashworth, fungicide product manager at Corteva, says limited quantities of Univoq will be available this season for the T2 timing after the product was only given UK approval in late March, and it will be key for disease-resistance management.
“It will relieve pressure on SDHI-azole products, which are used on most wheat crops, and so reduce the reliance on this chemistry,” he says.
The new product can only be used once in a season to help with resistance management, and will be focused on the T2 timing where the biggest yield benefits can be seen.
“The product, as it has a third site of action, will reduce the risk of resistance against SDHIs and azoles,” he adds. It will cost about the same a hectare as Revystar.
Yield advantage
In Corteva’s own work, Univoq showed a 0.25t/ha yield advantage over Revystar in eight trials in a direct comparison between the two at the T2 timing.
Mr Ashworth says the product has long persistence for septoria control, so a subsequent T3 ear spray can be focused on fusarium and rusts.
It is very effective against yellow rust, and on brown rust it should give four weeks of control at T2, so where brown rust is a problem, he suggests including a product with good brown rust activity with the T3 ear spray.
The addition of the multisite fungicide folpet can be useful, says Mr Ashworth, but the decision will be left to agronomists and growers.
The average application rate is expected to be 1.25 litres/ha, with the rate rising to 1.5 litres/ha in bad septoria situations, and down to 1.1 litres/ha when growing more resistant varieties with less septoria present.
