1 Should strobilurins still be used in wheat? Danish and foreign experience Lise Nistrup Jørgensen Karin Thygesen Danish Institute of Agricultural Sciences. Flakkebjerg

2 Danish Institute of Agricultural Sciences Flakkebjerg Agenda 2 years’ trial after strobe resistant septoria have become widespread Experiences from abroad Experiences with strobilurins for tan spot (DTR) control Next years recommendations

3 Danish Institute of Agricultural Sciences Flakkebjerg Distribution of strobilurin resistance septoria 2004 Strobilurin resistant septoria in DK >75% <75%

4 Danish Institute of Agricultural Sciences Flakkebjerg Septoria control with and without strobilurins – 5 trials split-ear treatment % control

5 Danish Institute of Agricultural Sciences Flakkebjerg Yield increases with/without strobilurins - 5 trials –split-ear treatments Hkg/ha LSD=3.4

6 Danish Institute of Agricultural Sciences Flakkebjerg Yield increase with/without strobilurins – 3 LC trials – single ear-treatments Hkg/ha LSD 95 = 2.1 Source: Landsforsøgene 2005

7 % control of septoria plus/minus strobilurins 3 trials – split-ear treatments Danish Institute of Agricultural Sciences Flakkebjerg

8 Danish Institute of Agricultural Sciences Flakkebjerg Yield increase plus/minus different strobilurins 3 trials split-ear treatment LSD = 2.9 Hkg/ha

9 Danish Institute of Agricultural Sciences Flakkebjerg Conclusions on Danish trials On average little positive effect of adding strobilurins in 2 years trials Gain similar to increasing dose of Opus Little or no greening effect observed Positive effects not dependent on cultivar or nitrogen

10 52 forsøg med høj resistens til strobiluriner QoI(>30%) French trials with 0.2 strobilurin or 0.2 Opus added to Opus treatments at T1 and T2 Kilde: Claude Maumene Arvalis, Frankrig + 0,2 strobilurin + 0,2 Opus

11 Danish Institute of Agricultural Sciences Flakkebjerg French data from strobilurin trials T1 and T2Yield increase from adding strobe or Opus hkg/ha + 2 x 0.2 strobi + 2 x 0.2 Opus + 2 x 0.2 Comet No of trials Resistant levelHigh >30%Low <30% Kilde: Claude Maumene Arvalis Basic treatments with 2 x ( l Opus)

12 Danish Institute of Agricultural Sciences Flakkebjerg Conclusions on French trials 82 trials with +/- strobilurins –3.3 hkg/ha from adding 0.2 l strobilurins to Opus (Margin by 0.8 hkg/ha) At high resistant levels Opus alone has been best –80% of trials have given best yield after increase in Opus dose (+0.2 l) compared with adding 0.2 l Strobilurins Comet + Opus solutions equally good as Opus solutions Best effect from adding strobilurins at the early application

13 Danish Institute of Agricultural Sciences Flakkebjerg Experiences from abroad Still low septoria resistance in some parts of Europe Still some effect on septoria – typically around 30% in fields with high levels of resistance Still yield increases around 3-4 hkg/ha. Big variation difficult to explain Possible explanations: –Occurrences of intermediate resistant isolates (10-15%) –Preventive effects still significant on resistant isolates –Direct physiological effects, diminishes stress/antioxidants –Comet has been seen to give induced resistance

14 Control of different septoria isolates with varying degrees of strobilurin resistance Danish Institute of Agricultural Sciences Flakkebjerg Sensitive isolate Inter- mediate isolates Resistant isolate

15 Danish Institute of Agricultural Sciences Flakkebjerg Preventive or curative effects on septoria IsolatesPreventive treatments Curative treatments Sensitive Resistant 1 Resistant 2 Resistant Source: Bill Clark, 2005

16 Danish Institute of Agricultural Sciences Flakkebjerg Recommendations abroad Opus/Proline/Daconil main elements in septoria control strategies in our neighbouring countries Effect of strobilurins on septoria is seen as secondary Strobilurins still recommended at late applications (T3) for control of –Alternaria, Claudisporium etc –Fusarium/Michodochium –Brown rust and yellow rust

17 Danish Institute of Agricultural Sciences Flakkebjerg % control of DTR on 2 nd leaf, GS trials Treatments at GS 39 HøveFlakkebjerg Untreated Bumper 0.25 Proline 0.4 Acanto 0.5 (45%) (75%)

18 Monitoring DTR sensitivity to strobes Agar + fungicide Spore suspension of pure- cultured isolates Microtitreplate with various fungicide concentrations mixed with agar 0,1 0 1, ppm/ L Strobilurin Propiconazole 50

19 Danish Institute of Agricultural Sciences Flakkebjerg DTR resistant monitoring - DK LocalitiesNumber of isolates Amistar EC 50 % Strobi- resistance* Bjærup (Flak) Ålborg Sjælland Nykøbing F Skive Odder Høve Flakkebjerg >25 > Totale (>10 ppm) * Probably G143 resistance

20 Conclusions on strobilurins resistance to DTR Strobilurins have shown reduced effects in field trials in Denmark as well as in Sweden 8 LC trials have on average given lower effects and yields from strobilurins compared with triazols Both F129 and G143 resistance-mechanisms found in Denmark. G143 gives low field performance Few isolates tested from These showed, however common resistance. Sensitivity tests from 2005 have shown wide spread resistance, but also variation between localities

21 Danish Institute of Agricultural Sciences Flakkebjerg Danish recommendations Septoria control –Opus alone or Opus + low Strobilurin dose –E.g.: 0.5 l Opus or 0.4 l Opus l Comet/Amistar DTR control –Bumper + Opus –E.g.: Bumper Opus –Proline (if and when registration comes in 2006)