Alternative treatments for control of powdery mildew in protected strawberries. Angela Berrie

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1 Alternative treatments for control of powdery mildew in protected strawberries Angela Berrie

2 Strawberry powdery mildew Caused by fungus Podosphaera aphanis Attacks all above ground plant parts including flowers and fruit Severe infection has a significant effect on yield and fruit quality In UK the disease is most important on crops under protection and especially everbearer crops and late season crops where failure to control can lead to crop abandonment Main cultivars grown very susceptible especially Elsanta, Sonata, Elegance, Amesti

3 Strawberry powdery mildew Disease overwinters either as mycelium surviving on old living green leaves which survive the winter Once temperatures rise in spring conidia produced on the mycelium initiate the new epidemic Or as the sexual state (Chasmothecia), surviving in leaf debris Ascospores released in spring initiate the new epidemic Importance of method depends on season Mildew may also be introduced on infected planting material

4 Strawberry powdery mildew Current control Based on fungicides Problems Not always effective particularly for everbearers, long season crops and late season crops DMI fungicides such as myclobutanil (Systhane) not as effective as previously Leads to multiple residues in fruit Loss of key fungicides through regulatory authorities Current approach therefore not sustainable New approach needed

5 Strawberry powdery mildew - Projects Objectives SCEPTRE project Objective strawberry diseases Powdery mildew To evaluate new fungicides for control of powdery mildew To evaluate biocontrols agents (BCAs) and alternative products especially elicitors or biostimulants for powdery mildew control AHDB Project SF157 Strawberry diseases - Objective 2 To evaluate programmes combining effective fungicides, BCAs and elicitors / biostimulants for control of powdery mildew

6 SCEPTRE project Identifying new products Two trials conducted on cv. Elsanta grown under polytunnels One trial evaluating new fungicides One trial evaluating BCAs and elicitors / biostimulants

7 SCEPTRE project Fungicide trial Elsanta planted in July 2013 under polytunnel. Cropped in 2014, mown off in June Trial conducted on regrowth 4 replicates 10 products tested Systhane (myclobutanil) as standard and untreated control Six sprays applied at 1000 L/ha from early July Mildew already present on the regrowth at the start of the trial Mildew assessed on 3 rd September as leaf area mildewed on 5 leaves on 5 plants per plot

8 SCEPTRE project Fungicide Trial - Products tested Treatment Product Active ingredient Fungicide Group UK rate of product / ha 1 Untreated Systhane myclobutanil DMI 0.45 L 3 STR-177 experimental DMI + QoI 1.0 L 4 STR-37 experimental Phenyl pyrrole 0.5 kg 5 STR-87 experimental Aryl-phenylketone 0.5 L 6 Luna Sensation fluopyram + trifloxystrobin SDHI + QoI 0.8 L 7 STR-25a experimental SDHI + DMI 1.0 L 8 STR-159 experimental 0.25 L +0.5 L 9 STR-47 experimental BTH 50 g SDHI + Arylphenyl-ketone 10 STR-17 experimental SDHI + DMI 1.2 L 11 Talius proquinazid Azanaphthalenes 0.25 L 12 Acanto picoxystrobin QoI 1.0 L

9 % leaf area mildewed SCEPTRE - Fungicide Trial - Results Untreated STR-47 STR-37 Systhane STR-87 STR-177 STR-25a STR-17 STR-159 Luna Sensation Acanto Talius Red = Significantly different from untreated

10 SCEPTRE project FungicideTrial - Results Untreated control Systhane Luna Sensation STR-159 Talius Acanto

11 SCEPTRE project BCA / biostimulant Trial Elsanta planted in July 2014 under polytunnel 5 replicates 10 products tested 7 biofungicides 3 plant extracts / elicitors Systhane as standard and untreated control Six sprays applied at 1000 L/ha from late July Mildew assessed on 20 th August

12 SCEPTRE BCA/biostimulant trial Products tested Treatment Product Active ingredient Type UK rate of product / ha 1 Untreated Standard Systhane Fungicide 450 ml 3 STR-188 Experimental Bacterial BCA 370 g 4 Serenade Bacillus subtilis QST 713 Bacterial BCA 10 L 5 STR-06+ SP057* Bayer BCA Bacterial BCA 10 L 6 STR-203 Experimental Plant extract 4 L 7 STR-105 Experimental Plant extract 2.5 L 8 STR-90 Experimental Plant extract 10 ml/l 9 STR-40 Experimental Fungal BCA 1 kg 10 STR-43 EXperimental Fungal BCA 10 g/l 11 AQ10 + SP057* Ampelomyces quisqualis Fungal BCA 70 g % 12 Cultigrow CBL Flavonoids Plant extract 1 L *SP057 = Silicon-based adjuvant

13 % leaf area mildewed SCEPTRE BCA / biostimulant Trial - Results Untreated STR-43 STR-90 STR-203 Serenade STR-40 CBL STR-188 AQ10 + SP057 STR-105 Systhane STR-06 + SP057 Red = Significantly different from untreated

14 SCEPTRE BCA / biostimulant trial - Results Untreated Control Systhane STR-06 + SP057

15 SCEPTRE - Identifying new fungicides, BCAs and biostimulants Conclusions 4 fungicide products identified giving excellent control Luna Sensation (fluopyram + trifloxystrobin), Talius (proquinazid), Acanto (picoxystrobin), STR-159 All biofungicides reduced mildew compared to untreated control STR-06 (Bayer BCA) and STR-105 performing as well as standard Systhane but not as good as the best fungicides

16 AHDB Project SF157 Improving integrated disease management in strawberry Objective 2 Strawberry powdery mildew Started 2015 To evaluate programmes combining effective fungicides, BCAs and elicitors / biostimulants for control of powdery mildew Trials conducted at two sites ADAS Boxworth (Dr Erika Wedgwood) NIAB-EMR Some treatment programmes followed at both sites

17 AHDB Project SF157 Trial detail 2015 NIAB-EMR Trial plot planted July 2014 cv. Elsanta. Spanish tunnels. used for SCEPTRE mildew trial In 2014 so expect high incidence of overwintering mildew Treatments applied CP15 Knapsack sprayer at 1000 L/ha Mildew assessed on 28 July as % leaf area mildewed on 5 leaves on each of 5 plants per plot using standard key ADAS Boxworth Trial was cv. Sonata in Coir grow-bags planted May 2015 Mildew assessed 4 times June-August

18 Project SF157 - Details of products evaluated Product Active ingredient Rate of product / ha Product type Systhane myclobutanil 450 ml Fungicide Fortress quinoxyfen 0.25 L Fungicide Amistar azoxystrobin 1.0 L Fungicide Nimrod bupirimate 1.4 L Fungicide Signum pyroxystrobin + boscalid 1.8 kg Fungicide Switch cyprodinil + fludioxonil 1.0 kg Fungicide Rovral iprodione 1.0 kg Fungicide STR-06 + SP057 Bayer BCA 5 L BCA AQ10 + SP057 Ampelomyces quisqualis 70 g % BCA STR-105 Plant extract 2.5 L Resistance promoter Cultigrow CBL flavonoids 250 ml Growth promoter F209 Experimental g Resistance promoter

19 Details of programmes applied Program Treatment Spray interval days No. of treatments P1 Untreated 0 0 P2 Standard fungicide Fortress, Nimrod, Systhane,Signum,Switch, Rovral 7 7 P3 Standard fungicide 14 3 P4 Reduced fungicide First 4 sprays only 7 4 P5 CBL 21 3 P6 CBL + P P7 STR-06 + SP P8 P4 + STR-06 + SP P9 AQ10 + SP P10 AQ10 + SP057 +P P11 F P12 F209 + P P13 STR P14 P4 + STR

20 Evaluation of programmes Results NIAB-EMR % Leaf area mildewed following treatment with various programmes applied pre-harvest assessed 28 July. Red = Significantly different from untreated Untreated 1 CBL + P3 CBL F209 + P3 F209 STR-105 Red. Fung. 1st 4 sprays Standard fungicide AQ10 + SP057 P4 + STR-06 +SP057 P4 + STR-105 STR-06 + SP057 P3 + AQ10 + SP057 St. fung. 7 days % leaf area mildewed

21 Evaluation of programmes - Results Incidence of mildew very low at both sites 8% or less leaf area mildewed on untreated plots Mildew incidence too low to really test the treatments At EMR trial was continued after harvest Strawberries were mown-off after harvest and trial continued on regrowth Same programmes followed but omitting treatments for Botrytis

22 Programmes applied in post-harvest trial NIAB-EMR Program Treatment Spray interval days No. of treatments P1 Untreated 0 0 P2 Standard fungicide Fortress, Nimrod, Systhane 7 7 P3 Standard fungicide 14 4 P4 Reduced fungicide First 4 sprays only 7 4 P5 CBL 21 3 P6 CBL + P P7 STR-06 + SP P8 P4 + STR-06 + SP P9 AQ10 + SP P10 AQ10 + SP057 +P P11 F P12 F209 + P P13 STR P14 P4 + STR

23 Post-harvest trial - Results % Leaf area mildewed following treatment with various programmes applied after harvest on regrowth assessed on 5 November. Red = Significantly different from untreated Untreated 1 F209 CBL Fung 14 days P3 + CBL Reduced fungicide P3 + F209 STR-06 + SP057 AQ10 + SP057 AQ10 + SP P3 STR-105 P4 + STR-105 P4 + STR-06 + SP057 Fung 7 days % leaf area mildewed

24 Mildew incidence on untreated and treated plots on final assessment 5 November Untreated 7 day fungicide 14 day fungicide STR-06 + SP057 AQ10 + SP057 STR-105

25 Conclusions Evaluation of fungicide / BCA / biostimulant programmes Incidence of mildew much higher on regrowth in post-harvest trial All treatments significantly reduced mildew Most effective were 7 day fungicide programme and programmes including STR-105 or STR-06 + SP057 Combinations of STR-06 + reduced fungicide, AQ day fungicide, STR reduced fungicide were significantly better than the 14 day fungicide or reduced fungicide programme alone Grower view control achieved not commercially acceptable

26 Strawberry powdery mildew control 2016 Programmes combining fungicides, biostimulants (CBL/Cultigrow) and BCAs (AQ10, STR-06) were evaluated These programmes were compared with 7 or 14 day interval fungicide programmes and an untreated control in experimental plots Trials at 2 sites EMR and ADAS on 60 day plantings of Elsanta or Malling Centenary to ensure high mildew risk High mildew incidence recorded in EMR trial (50-90% mildewed leaf area in untreated plots). Final assessments done in November

27 Strawberry powdery mildew control Proposed further work Best products / programmes identified in 2016 will be evaluated in larger plots / commercial farms The programmes will be evaluated as part of a management system taking into account mildew risk based on forecasting system (University of Hertfordshire), crop monitoring and the growth of the plant, which will affect choice of disease control product (protectant, eradicant, BCA etc) Hopefully this approach will give better control of mildew, particularly in long season everbearer production

28 ACKNOWLEDGEMENTS Thanks to AHDB and Defra for funding the SCEPTRE project AHDB for funding Project SF157 Trials team at NIAB-EMR for applying the sprays Gloria Endredi, Robert Saville, Karen Lower, Tom Passey, Joyce Robinson, Jennifer Kingsnorth for assistance with the trials