Oilseed rape disease control with a focus on light leaf spot: a UK perspective Dr Faye Ritchie, ADAS UK Ltd
Light leaf spot in the UK Why is light leaf spot so difficult to control? Can we forecast epidemics? What are the benefits of varietal resistance How do fungicides perform against light leaf spot Future control challenges Other oilseed rape diseases Phoma leaf spot/stem canker Sclerotinia stem rot Verticilliumwilt
Change in area of oilseed rape grown in 10 years (2000 to 2010) https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/183108/defrastats-foodfarm-landuselivestock-june-detailedresults-cropmaps111125.pdf
Light leaf spot (Pyrenopezizabrassicae) BASF Oilseed rape disease encyclopaedia Active at low temperatures (0 C) Inhibited by high temperatures (>20 C)
Light leaf spot is polycyclic continues cycling in the crop throughout the season Air-borne spores only Phomaleaf spot (monocyclic) Sep Nov Jan Mar May Jul Light leaf spot (polycyclic) Air-borne spores Cycles in the crop
Light leaf spot levels high in spring in England and Wales since 2008 Source: DEFRA oilseed rape disease survey
Stem symptoms caused by light leaf spot
Forecasting light leaf spot in the UK Percentage of crops with >25% affected plants at stem extension http://www.rothamsted.ac.uk/light-leaf-spot-forecast/historical-trends-light-leaf-spot
Investigating components of the oilseed rape light leaf spot epidemic responsible for increased yield loss to the UK To develop novel decision support tool to predict epidemic onset Verify model output through qpcr of spore samples Model disease cycling to improve understanding of epidemic Update current light leaf spot forecast AHDB Project: RD-2012-3814
Light leaf spot (Pb) spore release and rainfall at Rothamsted 2015 Crop emergence AHDB project RD3814 Massive dispersal of ascospores by harvesting infected crops and stubble cultivation Following initial infection by ascospores, LLS cycles in the crop by rain-splashed conidia which will not be picked up by spore trapping Pb = Pyrenopeziza brassicae
Minimum Recommended list rating (6) for the North region (2016/2017 list) https://cereals.ahdb.org.uk/varieties/ahdb-recommended-lists/winter-oilseed-rape-201617.aspx
Benefits to using more resistant varieties: slowing of disease epidemic Assessed on untreated plants near ADAS Rosemaund, Herefordshire, 2015-16
Light leaf spot incidence significantly lower on varieties with ratings of 6 and above Assessed on 17 March 2015; KWS trial conducted by ADAS UK Ltd. Data shown courtesy of KWS.
Varieties with lower resistance ratings more reliant on fungicides for yield KWS trial conducted by ADAS UK Ltd in 2015. Data shown courtesy of KWS.
Yields in relation to fungicide application timing Varieties with higher disease scores show a more robust performance when inputs are not applied or correctly timed for maximum control. Untreated yield difference = 100 (880 kr) /Ha or 35 (305 kr) per disease resistance point at current value of 295 (2590 kr) per tonne. Differences between the November/March treatment are of the value 60 (525 kr)/ha. The above would reflect the spray opportunities for many in the UK this autumn.
Light leaf spot control needs to be good from autumnonwards couldtakeupto4applications Fungicide in late October/November Further applications pre/at stem extension - monitoring from January onwards (applications weather permitting) Yellow bud application* Flowering application* *applied if control is poor earlier in the season and/or on very susceptible varieties
Pesticide use against oilseed rape diseases in the UK, 2014 reliance on azoles for phomaand light leaf spot Top 5 formulations: Prothioconazole + teb. Prothioconazole Tebuconazole Azoxystrobin Boscalid Top 5 varieties: DK Cabernet DK Extrovert PR46W21 Quartz Excalibur Defra funded Pesticide Usage Survey 2014
Light leaf spot treatments (AHDB Project 214-0006) Product Active(s) Full Dose (l/ha) Light Leaf Spot Untreated - - + Proline 275 prothioconazole 0.63 + Prosaro prothioconazole + tebuconazole 1.0 + Orius 20EW tebuconazole 1.25 + Orius P prochloraz + tebuconazole 1.5 + Refinzar*** penthiopyrad + picoxystrobin 1.0 + Pictor**** dimoxystrobin + boscalid 0.5 + Cirkon prochloraz + propiconazole 1.125 + *** Refinzar tested as a 2-spray programme in common with other light leaf spot treatments BUT the label restricts use to one application per season (at full dose) and no application after GS30 ****Pictor can only be used after 1 st February and GS20
Better activity from fungicides when used in a protectant situation AHDB Fungicide performance trial North Yorkshire (ADAS) 2014/2015
Between 40 and 60% control of light leaf spot in an eradicant situation AHDB Fungicide performance trial (SRUC), Edinburgh 2014/2015
Benefits to increasing fungicide dose above half rate vary do not always see yield responses in this trial series AHDB Fungicide performance trial (SRUC), Edinburgh 2014/2015
Azoles generally perform similarly against light leaf spot disease but do see yield differences Average across four AHDB Fungicide performance trials, 2013/2014
Need to take into account size of the crop due to growth regulatory effects (even in the autumn) Average across four AHDB Fungicide performance trials, 2013/2014
Non-azole fungicides introduced for control of light leaf spot in the UK Average across four AHDB Fungicide performance trials, 2014/2015
Non-azoles performing similarly to azoles against light leaf spot important for anti-resistance management Average across four AHDB Fungicide performance trials, 2014/2015
Future (and current?) challenge fungicide resistance Reports of reduced sensitivity to azoles in laboratory tests for light leaf spot in the UK Equivalent mutations to those conferring resistance to azoles in Z. tritici(+ novel mutations) Determine distribution of these strains and how to manage resistance development Carter et al., 2014 (Molecular Plant Pathology 15: 513-322)
Same mechanism causing resistance in P. brassicae as Z. tritici 100 Protectant 100 Eradicant 90 90 % control S. tritici full label rate 80 70 60 50 40 30 20 10 Variance accounted for = 43.2% 0 1996 1999 2002 2005 2008 2011 2014 80 70 60 50 40 30 20 10 Variance accounted for = 62.4% 0 1996 1999 2002 2005 2008 2011 2014 AHDB Fungicide Performance winter wheat trials Z. tritici data
Key points for LLS control a UK Perspective Assess management and control on farm-by-farm basis Bury crop residues (higher risk if present on stems/pods) Drill a resistant variety In-season monitoring Incubate leaves in the autumn and use forecasts Inspect crops regularly on a field by field basis from January onwards Fungicide application Spray in autumn (November) at high-risk sites Treatment timing is key: apply fungicide as soon as LLS found in January/February. May require further treatment(s) (green bud/flowering) Consider using higher doses where disease is already established Fungicide resistance Include non-azoles into the fungicide programme (possible?).
Other diseases Phomaleaf spot Sclerotinia stem rot Verticillium wilt
Phomastem canker: two autumn treatments (0.5 of the recommended label rate applied when 10 to 20% plants affected and again at reinfection) providing good control AHDB Fungicide performance 2015 fungicides applied in eradicant situation
Sclerotiniastem rot
Efficacy of fungicides against sclerotiniain 2015 unusual situation (0.25 dose gave good control) timing of infection Differences between products ns Differences between untreated control and fungicide treatments P>0.001
More typical benefits of increasing dose above 0.5 recommended label rate (2012): season long risk Disease: Untreated vs treated = P<0.001 Differences between products = ns Yield: P<0.001 LSD = 0.27
Fungicide dose important for good control at high risk sites AHDB Oilseed Rape Fungicide performance trials 2007 and 2008
Sclerotiniarisk in 2016 AHDB monitoring/weather based risk and BASF germination (5 May) http://cereals.ahdb.org.uk/monitoring/sclerotinia/sclerotinia-risk-report.aspx http://www.agricentre.basf.co.uk/agroportal/uk/en/tools/website_tools/sclerotinia_monitoring/osr_sclerotinia_monitoring.html
Weather criteria from the SkleroProInfection model can be used to identify infection events trialling alerts for UK growers Minimum requirements for sclerotinia infection: >7 C and 80% RH for 23hr Can also be applied retrospectively e.gto determine why fungicides have not controlled sclerotinia as expected Koch et al., 2006
How fungicide application timing affected sclerotiniacontrol in 2012 (fungicide persistence approx. 3 weeks) in relation to infection events during flowering (red arrows) Flowering 45 40 35 Rainfall (mm) 30 25 20 15 Yellow bud Early flower Late flower 10 5 0 01-Apr 08-Apr 15-Apr 22-Apr 29-Apr 06-May 13-May 20-May 27-May 03-Jun 10-Jun
Sclerotinia management UK perspective Fungicide will offer protection for approximately 3 weeks dose important for persistence Mid-flowering fungicides applied prior to significant petal fall most effective - timing critical for good control Two spray programmes used at high risk sites Tools available to evaluate risk help to determine whether a second fungicide application is needed
Verticillium wilt in oilseed rape First confirmed in UK oilseed rape crops in 2007 Pathogen is Verticillium longisporum specific for crucifers (mainly brassicas) first described 1997 Important in other parts of Europe with up to 50% yield loss
Disease concentrated in areas where oilseed rape has been grown for many years AHDB project 2009 to 2011 PR512
Evaluation of resistance levels to Verticillium wilt in UK oilseed rape varieties, and relevance to productivity produce a verticilliumwilt disease rating; determine yield loss caused by verticillium wilt. AHDB funded project: NIAB led (Jane Thomas) and ADAS
Improving verticillium management UK perspective Maintain long rotations at least 1 in 4 Monitor crops pre-harvest for premature ripening and symptoms Manage crops well small plants more vulnerable Variety choice important on affected land and avoid home saved seed
Oilseed rape diseases a UK perspective Light leaf spot requires a different fungicide strategy to controlling phoma leaf spot/stem canker and other diseases Opportunities to use non-azoles and azole/non-azole coformulations in all parts of the fungicide programme is key for anti-resistance management Fungicide timing important for all foliar diseases Understanding soil-borne diseases also important for sustainability of oilseed rape growing
Thank you