The response of spring barley varieties to strobilurin fungicides

Summary

Sector:
Cereals & Oilseeds
Project code:
PR237
Date:
01 April 1999 - 31 December 1999
Funders:
AHDB Cereals & Oilseeds.
AHDB sector cost:
£9,237 From HGCA (Project No. 2180)
Project leader:
R A BAYLES NIAB, Huntingdon Road, Cambridge, Cambridgeshire CB3 0LE

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pr237-final-project-report-part-1 pr237-final-project-report-part-2

About this project

Abstract

Amistar-based fungicide programmes gave an average yield benefit over a full conventional programme of 0.45 t/ha (+6.3%) in the three main trials and 0.53 t/ha (+8.8%) in the two late-harvested trials. In the trial in Scotland, the benefit of a full Amistar-based programme over a comprehensive conventional programme was 0.37 t/ha (5.7%).

Spring barley varieties that gave a high response to conventional fungicide programmes also gave a high response to Amistar programmes (e.g. Century and Prisma in trials in England and Optic and Henni in the Scottish trial). Similarly, varieties that gave a lower response to conventional fungicides tended to give a lower response to Amistar programmes (e.g. Static Riviera and Chariot in trials in England and Century and Delibes in the Scottish trial). The advantage of the Amistar programmes varied only slightly between varieties, ranging from 0.34 t/ha (+5.1%) for Prisma to 0.57 t/ha (+7.7 t/ha) for Century in England and from 0.23 t/ha (+3.6%) in Chariot and Cooper to 0.5 t/ha (+8.0%) in Newgrange in Scotland. As a result, the relative yields of varieties remained virtually unaffected by the change from conventional to strobilurin chemistry. The general implication for variety evaluation is that the overall relative performance of varieties is unlikely to be significantly affected by the introduction of strobilurin fungicides into the standard programme for Recommended List trials, although there may be exceptions in individual situations.

Different spray timings and total application of Amistar were compared in the trials in England. Reducing the total application of Amistar to half its level in the 'full' Amistar programme and reducing the number of sprays from two to one, did not reduce the yield advantage of these programmes over the conventional programme and led to improved margins over fungicide cost. This indicates the scope for cost effective exploitation of lower input strobilurin-based programmes in spring barley.

The advantage of Amistar could be attributed at least in part to increased green leaf area retention. All varieties showed some increase in green leaf area from around GS75 onwards, when the comparison was made between Amistar-based and conventional programmes. Improved green leaf area retention might be the result of a) improved control of major diseases that are easily identified and routinely assessed, b) improved control of minor diseases that are less easily identified and not routinely assessed or c) physiological effects. In all of these trials the major diseases were well controlled by all programmes, with only very slight differences in efficacy. It therefore seems likely that control of minor pathogens and/or physiological effects contributed to the enhancement of green leaf area retention by the Amistar programmes.
Cooper suffered less ear loss than the other varieties, with Optic and Prisma suffering particularly high losses. This was in line with the vulnerability of these varieties to brackling, which was relatively slight in Cooper and very severe in Optic. The effects of variety on both brackling and ear loss were far greater than effects of fungicide treatment. Ear losses were not significantly affected by fungicide treatment and there was no evidence to support the suggestion that late applications of Amistar might reduce ear loss. Similarly, although brackling was generally reduced by all fungicide treatments, there was no consistent difference between the conventional and Amistar programmes. This was despite the fact that Amistar treatments did appear to keep stems greener for longer.

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