Fungicide treatments : still aiming for diversity

The resistance of wheat leaf blight (Helminthosporium) to SDHIs (1) and of septoria to triazoles progressed further in 2015. However, there are still effective measures available, if advice to alternate, combine and plan are followed.

2016 collaborative note : an updated overview of the situation

The collaborative note, co-written by INRA, ANSES and ARVALIS - Institut du végétal is 12 this year !
In the 2016 edition, you will find an overview of the situation as regards to resistance to the fungicides used to control foliar diseases in cereals, as well as recommendations to limit its progress and maintain a satisfactory level of effectiveness of current solutions.
It is still recommended to limit the use of SDHIs to a single application per season on barley as well as on wheat.

Wheat leaf blight (or tan spot) : the situation is still evolving

At the end of the 2015 season, the number of tan spot strains that are resistant to SDHIs has increased compared to 2014 and represents on average over 50 % of the population, with vast differences between regions.
For this disease, it is still recommended to combine SDHIs and strobilurins with effective fungicides that have a different mode of operation (particularly prothioconazole or cyprodinil). But it is important to restrict either of those chemical groups to a single application per season.

Septoria : the situation is not alarming for SDHIs but more worrying for triazoles

As far as septoria is concerned, resistance to DMIs is on the increase and the most resistant strains now represent nearly 20 % of the population.
Despite this increasingly marked decline, epoxiconazole, prothioconazole and metconazole remain the most effective fungicides. Their activity on septoria must be consolidated with a formulation preferably combining a multisite fungicide (chlorothalonil, folpet) or a SDHI, or even prochloraz in the southern half of France where it is still useful.
In addition, it is recommended that a multisite is introduced into the treatment programmes from the first application targeting septoria.

No changes in resistance to SDHIs

In 2015, like in 2014, no septoria strain was found to be resistant to SDHIs in France. In other European countries, including those exerting more significant selection pressure regarding SDHIs, the detection of isolates specifically resistant to SDHIs remains exceptional. In view of this, there is no need to have concerns about the practical effectiveness of this chemical group in 2016.

(1) SDHI = Succinate DeHydrogenase Inhibitors