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01 February 2003
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30 January 2007

Etude de la répartition et du devenir de fongicides dans les plantes de blé et de leur impact sur le contrôle de maladies cryptogamiques

Study of fungicide distribution and evolution in wheat plants and effects on the control of fungal diseases

Context

In winter wheat growing, much debate still surrounds fungicidal control in terms of the appropriate number of applications, the best time for application and the rate to use. The aim is effective control of the different fungal diseases, taking account of the increasingly stringent environmental and economic aspects and minimising the possible emergence of pathogens resistant to the products used.

However, optimising fungicide use is hampered by a lack of references on product distribution in plants and evolution over time. Varying success with disease control in practice often gives rise to questions as to the presence in sufficient quantity of fungicides in the different parts of the wheat plants. Fungicide distribution on leaves already formed at the time of spraying, translocation to newly formed organs after treatment and persistence within leaves (or ears) are currently established intuitively, for the want of accurate data. Management of fungicidal control is therefore held back by lack of product behaviour knowledge.

Research into product effectiveness is currently based mainly on the persistent effect of the products in controlling a specific disease, on the principle that if an effect is observed, the product must be present. The literature thus offers little in the way of data on quantities of active ingredients effectively present in plant organs during the season.

Objectives

The aim of this research project is to establish whether the quantities of fungicide sprayed in the field and intercepted by wheat plant organs are sufficient to control fungal diseases. This is a two-phase project.
The first phase involves describing i) fungicide distribution at the different leaf levels and within an ear of wheat, ii) product translocation into the (newly) formed organs after spraying and iii) persistence in the plant over time. This research will be conducted in the field (natural conditions).
In the second phase, the biological effectiveness of fungicides will be studied under glass (controlled conditions), by spraying wheat plantlets with known quantities of fungicide and inoculating the plantlets with fungus spores.

Description of tasks

Field trials have been designed for the purposes of the first phase of the study. The aim is to harvest leaf samples, leaf level by leaf level (or ears) for chromatographic analysis, after spraying with a mixture of two fungicides of different chemical families. Two types of trial have been set up. Some of the tests will study fungicide distribution, redistribution and persistence according to the rate applied, time of application and number of applications. Others, meanwhile, will attempt to identify any differences in fungicide distribution as a function of the variety grown and stem density.
These trials are an opportunity to assess the biological efficiency, in natural conditions, of the various treatments in combating the main fungal diseases: Septoria leaf blotch and rust in leaves and wheat Fusarium head blight in ears.

Phase Two requires the development of standardised conditions for a defined quantity of fungicide in plantlets grown under glass. The best conditions for growing, production and inoculation of plantlets with Septoria conidia also need to be established.



The two phases cannot be carried out without developing an analytical method for determining product quantities present in the various organs of the wheat plant. A joint analytical method for the two products has been developed, optimised and validated by the Chemistry Section of this Department.

The fungicide distribution study will initially focus on the different leaf levels. The two fungicides used will be epoxiconazole (triazole class) and azoxystrobin (strobilurin class). The two products will therefore always be applied in a tank mix. Tebuconazole and picoxystrobin will be used later on, to confirm the results with the two aforementioned products.

Fungicide distribution in the ears will be studied subsequently. Ears treated with tebuconazole and azoxystrobin will be subjected to chemical analysis.

Partners

Development of analytical methods and chemical determination of residues are handled by the Chemistry Section of this Department (Dr O. Pigeon).
Close liaison is maintained with the D3 Mycology Laboratory at CRA-W (Dr A. Chandelier), the Phytopathology Unit at UCL (Prof. H. Maraite) and the Temperate Regions Crop Husbandry Department at FUSAGx (Prof. B. Bodson and F. Vancutsem).

Funding

  • SPW - DG Foreign policies
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