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Le 12/01/2013, 00:00:00 > Articles
Maladies du blé d'hiver au Luxembourg
Les interactions entre climat, sol et phytotechnie montrent l'importance primordiale du facteur climat
Malgré sa petite taille, le GDL comprend deux régions (Gutland au sud et Oesling au nord) très contrastées en ce qui concerne les maladies cryptogamiques du blé d’hiver. Une analyse en composante principale de la distribution de ces maladies a permis de noter que cette distribution est significativement différente (P < 0,001) entre régions. Summary Despite its small territory size, the GDL has several microclimates that result in a variability of wheat diseases severity between the South (Gutland) and the North (Oesling).
Entre 2003 et 2009, la septoriose et la rouille brune caractérisent le Gutland. Dans l’Oesling la sévérité de ces maladies était très faible. Mais l’Oesling est caractérisé par la sévérité de l’oïdium surtout en 2003 et 2009.
En parallèle, d’autres pathogènes fongiques sont observés uniquement en Gutland et les maladies qu’ils causent sont influencées par la phytotechnie. Il s’agit de l’helminthosporiose (favorisée par le développement du non-labour) et de la rouille jaune (contournement du gène de résistance Yr 17+).
La variation dans l’expression des maladies cryptogamiques entre le Gutland et l’Oesling est surtout due aux différences marquées des conditions climatiques entre les deux régions, mais aussi aux pratiques agricoles en vigueur (fumure azotée, choix variétal, semis avec labour ou sans labour…)
Septoria leaf blotch disease of wheat is important in the GDL. Over 2003-2009, the severity was strong in Gutland (51% on average over the last two upper leaves at the late milk growth stage) and low in the Oesling (16% for the same leaves). For the years 2006, 2008 and 2009, the disease severity was less than 6% in the Oesling while it exceeded 40% in the Gutland.
The second important fungal disease is the wheat leaf rust. Over the same period, the Gutland and the Oesling showed consistently the highest and lowest disease severity respectively. In 2003 and 2007, the Gutland showed the highest disease severity (66% and 57% respectively), and the lowest severity (<1%) was observed in the Oesling.
Another important disease is wheat powdery mildew. The 2003 and 2009 cropping seasons showed the highest disease severity with 15% and 40%, respectively, in the Oesling, whereas less than 1% severity was registered in the Gutland.
For wheat stripe rust, over 1999 to 2010, the difference between Yr17+ (Yr17 resistance gene) cultivars and cultivars not possessing this gene was highly significant (P<0.001) ; the highest severity is observed for the Yr17+ cultivars (mean severity of 13%) compared to the Yr17- cultivars (0.2%). This new virulent pathotype appeared more aggressive on the Yr17+ cultivars than on the others.
Tan spot caused by Drechslera tritici-repentis has become a common disease in winter wheat in Gutland in 1999, 2000 and 2009 ; non-inversion tillage and intensive winter wheat production were found to be the major factors influencing its severity.
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