Assessing the leaf blotch disease complex in wheat: A challenge for loss estimation and

1. Assessing the leaf blotch disease complex in wheat: A challenge for loss estimation and evaluation of warning systems Andrea Ficke, Morten Lillemo, Unni Abrahamsen, Oleif Elen and Guro Brodal

2. How much yield do we loose from leaf blotch diseases?

3. Why relevant? Justify our projects: Grant application Determine the economical threshold for spraying Rule of thumb: 1% severity = 1 % yield loss

4. Know your enemy… Winter wheat Spring wheat

5. Fungicide trials: • 8 years, • 2 different locations, • Different varieties, • Same assessment protocol • (25 plants, last 2-3 leaves, at Z 70-80) • Yield data • Different severity levels • Yt-Yu= b (Dt-Du) (Bhatalet al., 2003)

6. Yield increase with LBD reduction

7. WHY ?

8. Units? Kg/daa, hLw, or TKW? Difference between varieties? Different groups of disease reduction? What leaves to choose? Timing of assessments? What diseases involved?

10. Difference in varieties…. Demonstrant Yield increase/severity reduction ratio

11. Yield increase (%) LBD severity reduction (%)

12. Data from leaf assessments

13. % LBD infection/browning

14. Leafblotch Disease Complex (%) Sem Z75 10% less yield Heading In boot x

16. What other diseases are involved? Powdery mildew (B. graminis) early Fusarium Head Blight (Fusarium spp)

17. Conclusions: There is no defined relationship between LBD severity and yield reduction in Norway Experiments need to be designed to address true crop loss estimates Timing and tissue are critical for assessment All diseases involved need to be considered Time until harvest…

18. Thank you!