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Fungicide performance on winter wheat

HGCA PROJECT REPORT 488 

Fungicide performance on winter wheat 


by
Philip Bounds1, Jonathan Blake1, Bart Fraaije2, David Parsons3, Stuart Knight4, Fiona Burnett5, John Spink6 and Jim McVittee7

1ADAS Rosemaund, Preston Wynne, Hereford, HR1 3PG
2Rothamsted Research, Harpenden, Hertfordshire, AL5 2JQ
3Cranfield University, Cranfield, Bedfordshire, MK43 0AL
4NIAB TAG, Huntingdon Road, Cambridge, CB3 0LE
5SAC Edinburgh, West Mains Road, Edinburgh, EH9 3JG
6TEAGASC, Oak Park Research Centre, Carlow, Ireland
7HGCA, Agriculture & Horticulture Development Board, Stoneleigh Park, Kenilworth, CV8 2TL

Abstract

Between 2008 and 2010 the efficacy of eight fungicides was tested in 21 replicated trials in wheat in the UK and Ireland. Four sites each year tested products on Septoria tritici. Three sites (one site per year per disease) tested product efficacy on powdery mildew, brown rust and yellow rust. The fungicides chosen were either new active ingredients, from the succinate de-hydrogenase inhibitor (SDHI) group, or new mixtures of existing chemistry, tested alongside core treatments representing current standards. The new fungicides have since been approved and are registered for use. Fungicides were evaluated as single applications at a range of doses, so that dose response curves could be fitted for each disease. In contrast to previous fungicide performance work, the trials tested products at T1 and T2 spray timings, and also includedtreatments applied at half dose at two application timings, to better reflect how products would perform in a more commercial situation. The main conclusions were as follows:

On Septoria tritici, the rank order of performance of fungicides was similar whether applied at T1 or T2 timings, and in both eradicant and protectant activity. Bravo (chlorothalonil) continued to show useful protectant activity. Opus (epoxiconazole) and Proline (prothioconazole) still provided good eradicant and protectant activity, and were equally matched. Brutus (epoxiconazole and metconazole) and Ennobe (epoxiconazole and prochloraz) provided better eradicant and protectant activity than could be explained simply by the higher triazole loading of these products. This may be due to a change of formulation or a synergy between the two triazoles. The new SDHI products Aviator Xpro (bixafen and prothioconaozole), Seguris (isopyrazam and epoxiconazole) and Adexar (fluxapyroxad and epoxicaonazole) gave better eradicant and protectant activity than the current standards, and there were higher than expected yield increases from these products when compared to Brutus and Ennobe.

On yellow rust all products were effective where a half dose or more of the product was applied. Products containing epoxiconazole (Brutus, Opus and Adexar) appeared to provide the highest levels of control. The addition of fluoxastrobin to prothioconazole (in Firefly) improved the level of control compared to prothioconazole (Proline) applied alone.

On brown rust, the strobilurin (e.g. pyraclostrobin) and SDHI (e.g. isopyrazam) fungicides tested were effective. When tested in mixture with prothioconazole (as Firefly and Aviator Xpro) or epoxicaonazole (as Adexar), they added significantly to activity compared to the triazole alone.

On powdery mildew, the specific mildewicides Talius (proquinazid), Cyflamid (cyflufenamid), Tern(fenpropidin) and Flexity (metrafenone) were effective in 2008, the only season with significant disease levels. SDHIs also appeared to control powdery mildew.

A fungicide calculator was developed to predict how sequences and mixtures of fungicides might perform. Data from the trials were used to validate the calculator. The calculator generally predicted performance within the variation between replicates of the experimental data.

Significant differences in Septoria tritici sensitivity to azoles were recorded between sites. Additionally the use of specific azoles appeared to result in higher proportions of certain mutations in the remaining population. This could lead to the build up of insensitive isolates where the same azoles, (or azoles that select in the same way) are used repeatedly.

HGCA Project Number: 3397
Price: £9.38

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