Key Points
- Fungicide treatments on a ‘less susceptible cultivar’ (Claire) gave significant yield increases for the third year in succession. In 2002/03 where leaf rust was the principal disease, yield response to fungicide ranged from 10 to 16%.
- The most cost effective programmes were those based on two spray timings.
- One spray approaches gave inferior green leaf retention, disease control and yield, whilst three spray programmes starting at GS32 (leaf 3 emergence) gave no advantage over 2 sprays in terms of disease control or yield.
- Of the products tested over two seasons and three trials, the best treatments have been based on Amistar 0.25 + Opus 0.25 applied twice (GS39-flag leaf emergence and GS65-mid flowering), except where mildew was the principal disease, in which case Allegro at the same timings was slightly superior.
- Overall, no yield response has been shown to additional fungicide applied at GS32 with this less susceptible variety. However, if the GS32 spray is omitted, remember to monitor the crop for disease between GS32 & GS39 in case there is a need to spray (e.g. breakdown in variety resistance or a severe early season epidemic).
- In keeping with the new anti-resistance guidelines for strobilurins the work has illustrated that 3 strobilurin applications are unnecessary for less susceptible cultivars.