By Damian Jones, ICC
This trial is continuing on with our fungicide work, but with a program that is considering Septoria Tritici Blotch as well as Stripe Rust.
Septoria tritici blotch is an important stubble borne foliar disease of wheat in Victoria. This disease has increased in importance in the high rainfall cropping regions during the last ﬁve years, even though it has been well controlled in Victoria for the last 30 years through the use of partially resistant wheat varieties. The increase in Septoria in the high rainfall zone has been favoured by stubble retention, intensive wheat production, susceptible cultivars and favourable disease conditions.
Septoria tritici blotch survives from one season to the next on stubble. Following rain or heavy dew in late autumn and early winter, wind borne spores (ascospores) are released from fruiting bodies (perithecia) embedded in the stubble of previously infected plants. These spores can be spread over large distances.
Septoria tritici blotch. The presence of black fruiting bodies within the blotches is a diagnostic feature of Septoria tritici blotch.
In contrast, Yellow Leaf Spot (above) has no black dots (perithecia) in the blotches.
Early ascospore infections cause blotches on the leaves. Within these blotches a second type of fruiting body, pycnidia, are produced. Asexual spores ooze from pycnidia when the leaf surface is wet and spores are dispersed by splash to other leaves where they cause new infections. This phase of disease development depends on the rain splash of spores; therefore Septoria tritici blotch will be most severe in seasons with above average spring rainfall. A combination of wind and rain provides the most favourable conditions for spread of this disease within crops (from DEDJTR disease notes).
The trial was sown to Scout (MS for stripe rust; S-VS for septoria and S-VS for yellow leaf spot).
The fungicide products used (with thanks to Adama and Landmark McNeil Saunders) are:
Fungicide Registration for disease control in Wheat
The timing of the fungicide spray was at Z32 (second node) which is targeting STB control and Z39 (full ﬂag emergence), targeting stripe rust control.
TX = Tilt Xtra, O = Orius
The control treatment received a fungicide application at Z39 as this would be regarded as a standard treatment for an irrigated crop.
The “Prosaro HR” treatment used Prosaro at a higher than label rate as a PGR as well as a fungicide. The PGR eﬀect of the high rate of Prosaro was minimal where disease and infection pressure may have been higher, similar to the strategy used for the fabas.
No treatment had any eﬀect on grain yield or quality. Visual inspection of the plots noted very little disease present in any treatment.
The stubble project – maintaining profitable farming systems in Victoria and Tasmania with retained stubble (project number BWD00024) is funded by the GRDC.
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