New feed wheat variety offers SDHI fungicide savings

A new variety of feed wheat with the highest resistance to septoria could be the safest option for growers looking to pursue a single SDHI fungicide strategy next season.

Trial work in 2016 by breeding group Limagrain, on Sundance, a soft Group 4 wheat from its stable, showed no yield response from adding a second SDHI to a programme already containing one SDHI application at T2.

Sundance is one of six new soft feed wheat varieties on the AHDB Recommended List this season and tops the septoria resistance rankings with a rating of 7.3, beating nearest rival Siskin into second place by 0.5 points.

See also: Plant tissue tests lead to bumper wheat yields in Scotland

The new variety has paid no yield penalty for the additional disease resistance, coming joint top in the soft feed wheat category alongside Bennington, at 104%.

Using fungicide sprays sparingly when appropriate will help growers cut costs and preserve vital chemistry by limiting the opportunities for disease to build up resistance.

Ron Granger, arable technical manager with Limagrain, says its data shows T2 is the key wheat fungicide spray and is the time to use an SDHI, but providing crops are monitored carefully he’s “not convinced” they are needed at T1.

The trial studied the impact of four different fungicide programmes on crop yield (see table) and found a 2.2t/ha yield increase between untreated crops and those given a “very high” fungicide dose.

When an additional SDHI was added for extra protection at T1 in the “very high” fungicide trial, the crop didn’t respond by yielding any higher than the 12.9t/ha seen in the “high” trial.

Mr Granger stressed that programmes based on azoles, strobilurins and multisite products such as chlorothalonil and folpet, are vital to maximising yield potential.

In the trial, the “high” dose included an azole, strobilurin and chlorothalonil at T1, an SDHI, azole and a chlorothalonil at T2, and an azole at T3.

The fungicide trial found there was no yield benefit from adding a second SDHI at T1 (SDHI chemicals in bold)    

Fungicide programme

T0

T1

T2

T3

Yield

(t/ha)

Untreated

Untreated

Untreated

Untreated

Untreated

10.7

Low

Untreated

Firefly (fluoxastrobin + prothioconazole)

Bravo (chlorothalonil)

Ignite (epoxiconazole)

Bravo (chlorothalonil)

Untreated

12.2

High

Talius (proquinazid)

Phoenix

(folpet)

Firefly (fluoxastrobin + prothioconazole)

Bravo (chlorothalonil)

Adexar (epoxiconazole +

fluxapyroxad)

Bravo (chlorothalonil)

Proline (prothioconazole)

 

12.9

Very high

Talius (proquinazid)

Phoenix

(folpet)

Cortez (epoxiconazole)

 

Vertisan (penthiopyrad)

Firefly (fluoxastrobin + prothioconazole)

Bravo (chlorothalonil)

Adexar (epoxiconazole +

fluxapyroxad)

Bravo (chlorothalonil)

Proline (prothioconazole)

 

12.9

Sharing the disease resistance burden

 John and Charles Roe

Lincolnshire farmers John and Charles Roe

Growers and breeders alike agree that fungicides and plant genetics will have to work together to protect each other in the years ahead in order to preserve the power of vital sprays for as long as possible.

John and Charles Roe, a Lincolnshire based father-and-son team specialising in seed growing, have been impressed by how clean of disease Sundance has been on their farm this season.

They believe it will be the variety that offers the least risk of using a cheaper programme compared with varieties with lower disease resistance, saying that growing a dirtier variety with huge reliance on inputs is “stupid” when a high resistance variety can be planted.

The variety’s punchy agronomic package fits in well with their careful strategy of pursuing every avenue that will help the October-drilled crop clean.

This includes a long crop rotation featuring double spring breaks of linseed and peas, as well as running a sprayer that is over capacity for their 242ha farm in order to get timings as close to optimum as possible.

Crops are also kept as weed-free as possible on the land at Shirewood House Farm near Revesby, with the lack of blackgrass on the farm being credited to hand roguing twice a year and not allowing any contractors on their land.

However, Charles says having a variety with a minimum rating against septoria of 7 is still a “no brainer” for their system, as having a variety with as high an untreated yield as possible is key for yield preservation.

This is important on their dry, sandy clay loam soils between the Lincolnshire fenlands and wolds, and with their five-year average yield coming in at just over 9t/ha, they place a premium on minimising yield loss, rather than selecting for all-out yield.

They say the Achilles heel of Sundance is its low specific weight, and have a plan in place to manage that at the T3 stage, with a robust protectant fungicide spray along with biostimulants and any micronutrients required to preserve green area for as long as possible.

Mr Granger advises that T3 is particularly important in a later-maturing variety such as Sundance, and advises using an azole product to ensure the best chance of good grain fill by maturity.

The future battle against septoria

The future for improving plant resistance to septoria is bright, with high-yielding varieties possessing a resistance rating of 8 in the pipeline, and varieties being discovered annually with new types of genetic resistance.

The AHDB Recommended List ranks disease resistance from 1 to 9, with 1 being susceptible and 9 meaning good tolerance.

Sundance is rated for septoria resistance at 7.3 but Paul Fenwick, cereal pathologist with Limagrain and its predecessors for 40 years, says that a high-yielding variety with a resistance of 8 will be available in the “near future”.

He explains using an approach known as association genetics, breeders are able to identify potential new plant varieties that possess useful disease resistant genetics more rapidly.

He recalls Septoria tritici overtaking Septoria nodorum as the number one wheat disease in the 1980s, and puts the swift spread of the disease down to the limited number of varieties being grown at the time, with vast areas of varieties such as Norman and Longbow.

The disease quickly overwhelmed any genetic resistance that the plants possessed, as it was often from a single gene, which can be easily circumvented by the disease mutating.

But Mr Fenwick says by using association genetics, breeders are able to bring together different plants with different resistance genetics and breed new varieties with a more complex level of resistance, which will be harder for the disease to break down.

Last year alone, five new resistance genes were identified by Limagrain, which may be able to help fight the disease in future, and the task now is to see if these can be turned into a commercially viable type.

Mr Fenwick cautions that the disease also needs careful monitoring for mutations so that breeders can respond as quickly as possible if the disease changes the way it attacks a plant, as has been seen recently in yellow rust, with the advent of the “warrior” race.