The effect of strobilurin fungicides on the development of foliar diseases of winter wheat

I. Gaurilčikienė and A. Ronis

Lithuanian Institute of Agriculture, Instituto al. 1, LT–58344 Akademija, Kėdainiai distr.,Lithuania; e–mail: irenag@lzi.lt

Abstract:

The present paper reports the results of field research into the epidemic progress of fungal leaf diseases in winter wheat cv. Zentos. Experiments were conducted during the period 2003–2004 and were designed to study the impact of strobilurins krezoxim–methyl+ epoxyconazole+fenpropimorf, trifloxystrobin+propiconazole, azoxystrobin, piraclosrobin+ epoxyconazole and picoxystrobin on the epidemic progress of Stagonospora leaf blotch (Stagonospora nodorum (Berk.) Cast. and tan spot (Pyrenophora tritici-repentis (Died.) Drechs.) and to compare with triazoles epoxyconazole and propiconazole. In both years the pressure of fungal leaf diseases was severe. The unusually hot period during the wheat ripening stage in 2003 provoked the intense outbreak of tan spot. However, the warm and rainy prolonged ripening season in 2004 promoted the severe infection of Stagonospora blotch. Our experimental findings suggest that both strobilurin and triazole fungicides significantly suppressed the epidemic progress of Stagonospora leaf blotch and tan spot on the upper three leaves of winter wheat. The lowest AUDPC (Area Under the Disease Progress Curve) value in both years (2003 and 2004) was recorded in the treatment with piraclosrobin+epoxyconazole, while the highest, in the treatment applied with triazole propiconazole. AUDPC of the other strobilurin fungicides ant triazole epoxyconazole were comparable. AUDPC of both Stagonospora leaf blotch and tan spot on the upper leaves (F, F–1 and F–2) showed the strong negative linear correlation with the grain yield and 1000 grain weight (TGW).

Key words:

AUDPC, Stagonospora leaf blotch, strobilurin, tan spot, triazole, winter wheat

Development of tan spot (Pyrenophora tritici-repentis) in winter wheat under field conditions

A. Ronis and R. Semaškienė

Department of Plant Pathology and Protection, Lithuanian Institute of Agriculture,Instituto aleja 1, Akademija, Kedainiai distr., LT 58344; e-mail: antanasr@lzi.lt

Abstract:

The pathogen that causes tan spot on wheat is Pyrenophora tritici-repentis (Died.) Drechs. (anamorph Drechslera tritici-repentis (Died.) Shoemaker). In recent years tan spot has become a potentially destructive disease of wheat in Lithuania and neighbouring countries. Three winter wheat cultivars (Aron, Tauras and Hereward) were grown during three seasons. Weather conditions were observed from April to August when the tan spot pathogen spreads. During the experimental years the weather conditions varied from season to season. A severe epidemic of tan spot occurred in 2004 when there was a sufficient amount of rain and the air temperature was close to optimal. The other two seasons were not extremely favourable for tan spot occurrence, especially in 2005, because of the lack of rain during the main growing period.Investigations of tan spot development patterns under field conditions enable wheatgrowers to better forecast tan spot and achieve better timing of fungicide applications.

Key words: