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European network trials with fungicide to control septoria in wheat still show beneficial effect of old azoles but best effect of new azole

A comprehensive analysis of 55 field trials across ten different European countries provides an insight into the effect of different azoles on the disease septoria, which each year causes large yield losses in European wheat cultivation.

[Translate to English:] Foto: Septoria i hvede - Lise Nistrup Jørgensen

The fungus Zymoseptoria tritici causes septoria. It is the most prevalent fungal disease in wheat in Western Europe. Especially in humid growing seasons, septoria causes great damage to the European wheat fields, and this naturally has a negative effect on the farmer's yield. To reduce infestation and loss, spraying with fungicides is common. The wheat varieties grown in Europe are only partially resistant, and an adjustment in crop rotation or a delay in sowing does not significantly alleviate the disease attack. 

“The septoria fungus produces large amounts of infectious material on stubble residues in the autumn, which spread from field to field also over greater distances. This means that a changed crop rotation has little or no effect,” explains senior researcher Lise Nistrup Jørgensen from the Department of Agroecology.

Intensive use of azoles to combat septoria has created problems with resistance, which more and more farmers are experiencing problems with. The resistance is seen in relation to the "old" azoles, which have been on the market for decades.

In a European network - Eurowheat - field trials have been carried out across 10 different European countries. Here, researchers have tried to create an updated overview of the effect of azoles on relevant diseases in wheat, both septoria and rust diseases have been included. This has the answer to where do the products work well, how has the effect developed over time, where are the biggest problems with resistance and - not least - is there a difference in the effect of the different active substances? The experiments were carried out together with partners in Scotland, England, Poland, France, Germany, Ireland, Belgium, Latvia, Lithuania, and Hungary. The project has been financially supported by BASF, which produces and sells fungicides, and it is led by the Department of Agroecology at Aarhus University.

55 field trials spread across Europe

Azoles are substances that act on many different types of fungi. There are thus many different azole products which are used in e.g. medicines and tree protection, but also in agriculture, where they are included in many fungicides. In agriculture, azoles, among other things, have been used to control fungal diseases on leaves in wheat for more than 40 years. And today, the azoles are still considered an important group, and are part of many blend products and control strategies despite the growing problems of resistance.

“We performed a total of 55 field trials in the period 2015-2018, where we among other things tested the four most common azoles: epoxiconazole, prothioconazole, tebuconazole and metconazole. In the experiments, we found that the effect of the azoles generally varied greatly across Europe. We also saw that the effect was reduced over the trial period,” says Lise Nistrup Jørgensen.

She further explains that:

“On average, the azoles protect approx. 60% against septoria, but it varies a lot - not just between the different regions - but also from year to year. In about 30% of our field trials the azoles could control less than 50% of the septoria, and in some trials from England, France and Germany some field trials even showed disease reductions of less than 30%, which must be said to be unacceptable effects. Thus, although there are areas where the impact is challenged, we can also conclude that the azoles are still beneficial in the fight against septoria in most parts of Europe. Not least as a mixing partner - which helps reduce the development of resistance to other groups of fungicides.”

New azole gave higher effect (about 80%)

In two of the growing seasons, a new azole - mefentrifluconazole - was also included in the trial. This azole showed a significantly higher effect than the four "old" azoles. 

The results with this new azole confirm that there is no clear cross-resistance between the azoles, which means that the new azole is not inhibited by the mutations found in the septoria population, which inhibit the effect of the "old" azoles. The new azole has been introduced to the market from 2020, and is currently of great importance for the control of septoria in Europe,” says Lise Nistrup Jørgensen.

The use of fungicides is controversial and problematic in relation to the public's desire for a lower consumption of pesticides. In addition, there are expected to be further restrictions on the number of approved azoles legal in the EU. So, there are plenty of challenges to tackle if we are to cope with fewer fungicides at European level in the future to control septoria in wheat.

“Although we are experiencing increased resistance to azoles in several places in Europe, both the "old" and the new azole give useful effects against septoria. That's a good thing, but it does not mean we can sit back and relax. We need to focus more on increasing the prevalence of septora-resistant varieties, which reduces the need for spraying. It is also important that we have built-in strategies against fungicide resistance that can optimise the way we utilise the fungicides, including fewer sprays, spraying according to needs assessment, spraying with mixtures of active substance groups, and spraying with low and adapted dosages. These elements will help ensure that we can continue to grow wheat in Europe in the future without major losses from septoria,” says Lise Nistrup Jørgensen.

Additional information
We strive to ensure that all our articles live up to the Danish universities' principles for good research communication (scroll down to find the English version on the web-site). Because of this the article will be supplemented with the following information:
Study type: Follow-up study
Collaborators:Department of Agroecology at Aarhus University, SRUC, NIAB, ADAS Rosemaund, Institute for Plant Protection at Sosnicowice, Institute for Plant Protection at the National Research Institute in Poznan, Arvalis Institut de végétal Station Experimentale, JKI Brunswick Germany, Bayerische Landesantalt für Landwirtshaft, Teagasc Oak Park in Ireland, CRA-W Plant and Ecotoxicology Protection in Belgium, Latvian Plant Protection Research Center, Plan Protection Institute at St. István University, Swedish Board of Agriculture, Lithuanian Research Center for Agriculture and Forestry at Akadimija and BASF SE in Germany
Funding: BASF SE – grant no. 22498
Conflict of interest: None
Læs mere: 

The ”Decreasing azole sensitivity of Z. tritici in Europe contributes to reduced and varied field efficacy” is published in the Journal of Plant Diseases and Protection. It is written by Lise Nistrup Jørgensen, N. Matzen, T.M. Heick, S. Holdgate, B. Clark, J. Blake, M. Glazek, M. Korbas, J. Danielewicz, C. Maumene, B. Rodemann, S. Weigand, S. Kildea, C. Bataille, E. Brauna- Morzevska, K. Gulbis, R. Ban, G. Berg, R. Semaskiene, and G. Stammler.

The article “Efficacy of common azoles and mefentrifluconazole against septoria, brown rust and yellow rust in wheat across Europe” is published in the book “Modem Fungicides and Antifungal Compounds”, Vol. IX, pp. 27-34. © 2020. Deutsche Phytomedizinische Gesellschaft, Braunschweig, ISBN: 978-3-941261-16-7 It is written by Jørgensen LN, Matzen N, Havis N, Holdgate S, Clark B, Blake J, Glazek M, Korbas M, Danielewicz J, Maumene C, Rodemann B , Weigand S, Kildea S, Bataille C, Brauna-Morževska E, Gulbis K, Ban Rita, Berg, G.

Contact: Senior Researcher Lise Nistrup Jørgensen, Department of Agroecology, Aarhus Universitet. Tel. +45 2228 3352 or mail: lisen.jorgensen@agro.au.dk