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

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1 Alternative treatments for control of powdery mildew in protected strawberries Angela Berrie 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 Strawberry powdery mildew Current control Based on fungicides Problems Not always effective particularly for everbearers, long season crops and late season crops DMI fungicides 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

2 Strawberry powdery mildew - Projects SCEPTRE Identified new fungicides 4 fungicide products identified giving excellent control Luna Sensation (fluopyram + trifloxystrobin), Talius (proquinazid), Acanto (picoxystrobin), STR-159 BCAs - STR-06 (Bayer BCA), STR-105 and AQ10 Alternative chemicals elicitors / plant strengtheners B204 Strawberry powdery mildew - Projects AHDB Project SF157 Improving integrated disease management in strawberry Strawberry diseases - Objective 2 Further evaluation of effective fungicides, BCAs and elicitors / biostimulants for control of powdery mildew To develop programmes based on fungicides and alternative chemicals AHDB Project SF157 Strawberry powdery mildew Objective 2 Strawberry powdery mildew 2016 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 Same treatment programmes followed at both sites

3 Plot details NIAB EMR Trial plot planted August cv. Elsanta Two Spanish tunnels, 3 rows per tunnel. Outer 2 rows used for plots. Central row as guard row Plastic mulch raised bed. 30 plants per plot in double staggered row Covered polythene 18 August Treatments applied CP15 Knapsack sprayer at 1000 L/ha Plots regularly inspected for mildew Mildew assessed 3 times as % leaf area mildewed on 5 leaves on each of 5 plants per plot using standard key Strawberry powdery mildew Products Details of products used in powdery mildew control in strawberry 2016 Product AQ10 + Silwet Active ingredient Ampelomyces quisqualis Rate of product per ha 70 g % B204 Plant extract 250 ml Other Product type Target information 21 d harvest interval BCA Strengthener Mildew Plants Fortress quinoxyfen 0.25 L Fungicide Mildew Nimrod bupirimate 1.4 L Fungicide Mildew Rovral iprodione 1.0 kg 4 sprays max Fungicide Botrytis STR-06 + Silwet pyroxystrobin + boscalid 1.8 kg 2 sprays max Fungicide Mildew/Botrytis BCA from Bayer 5 L % BCA Mildew 2 sprays Switch cyprodinil + fludioxonil 1.0 kg max Fungicide Mildew/Botrytis Systhane myclobutanil 450 ml Fungicide Mildew Details of programmes applied Programme Treatment Spray interval days No. of treatments P1 Untreated 0 0 P2 Standard fungicide Fortress, Nimrod, Systhane,,Switch, Rovral 7 8 P3 Standard fungicide 14 4 P4 B P5 B204 / STR-06 + Silwet 21 / 7 3 / 5 P6 STR-06 + Silwet 7 7 P7 B204 /STR-06 + Silwet /Fungicide 21 / 14 / 14 3 / 3 / 4 P8 B204 / AQ10 + Silwet 21 / 7 3 / 5 P9 AQ10 + Silwet 7 7 P10 B204 /AQ10 + Silwet /Fungicide 21 / 14 / 14 3 / 3 / 4 P11 B204 /AQ10 + Silwet or AQ10 + Rovral 21 / 7 / 7 3 / 2 / 3

4 Predicted mildew risk NIAB EMR 2016 Predicted daily risks from EMR model period 4 consecutive days with risk > 10% = intervention needed Results Mean % leaf area mildewed (mean of 3 assessments) Treatments with different letters are significantly different Results Mean % mildewed fruit (mean of 4 harvests) Treatments with different letters are significantly different

5 Results Mildew incidence Untreated P1 P2 7 day fungicide P6 STR-06 + Silwet P9 AQ10 + Silwet Strawberry powdery mildew Conclusions 2016 All spray treatments significantly reduced mildew incidence on both leaves and flowers/fruit Lowest mildew incidence on plots treated 7 day fungicide AQ10 +Silwet, STR-06+Silwet did not differ significantly from 7 day fungicide AQ10 + Silwet or STR-06 + Silwet applied alone gave better control than applied in programmes with other products AQ10 + Silwet or STR-06 + Silwet gave better mildew control on flowers and fruit than standard fungicide programme Obvious visual differences in plant vigour between treated and untreated but only 7 day fungicide significantly > vigour AHDB Project SF157 Objective Strawberry powdery mildew Main objective 2017 To compare the disease control achieved by managed programmes of fungicides, biofungicides, elicitors/plant strengtheners with or without routine applications of silicon or B204 with that achieved by a routine fungicide programme or an untreated control Trial conducted at one site at NIAB EMR

6 Plot details NIAB EMR 2017 Trial plot planted 21 June 2017 cv. Amesti Two Spanish tunnels, 3 mypex-covered rows per tunnel. Outer 2 rows used for plots Plot consists of coir bag on upturned plastic crate 5 plants per bag and 14 bags per plot = 70 plants Treatments applied CP15 Knapsack sprayer at 1000 L/ha Low incidence mildew in plants at time of planting All plots sprayed with Amistar 23 June and then Fortress on 3 July Trial started on 10 July Products for Botrytis control were same for all treatments Plot details Assessments Data loggers to measure temperature and humidity in each tunnel for input to mildew model Plots regularly inspected for mildew 2x per week for management decisions Mildew assessed on leaves as % leaf area mildewed on 5 leaves on each of 10 plants per plot using standard key every 3 weeks Fruit harvested once or twice a week from 28 July 14 harvests in total Yield and fruit number recorded and fruit quality Fruit assessed for mildew and rots Powdery mildew Treatments Management treatment programmes evaluated in 2017 Treatment Type Products Other 1 Untreated Routine Fungicides None 3 Managed Fungicides, B204 applied BCAs, elicitors, monthly from plant start of growth strengtheners 4 Managed Fungicides, Sirius applied BCAs, elicitors, weekly from plant start of growth strengtheners 5 Managed Fungicides, BCAs, None Inclusion of Sirius based on work done by Dr Avice Hall at University of Hertfordshire

7 Product Fungicides for powdery mildew control Active ingredient Product type Other information Harvest interval days Chemical group Luna Sensation trifloxystrobin + fluopyram Potassium bicarbonate ASP Max 2 sprays 1 SDHI + QoI Powdery mildew 2017 Alternative treatments Alternative products in managed programmes evaluated in 2017 Product STR-06 + Silwet AQ10 + Silwet Active ingredient BCA from Bayer Ampelomyces quisqualis Rate of product / ha 5 L % 70 g % B204 flavonoids 250 ml Sirius silicon Systhane myclobutanil ASP Max 6 sprays. Not after September 30 3 DMI 2017 Fortress quinoxyfen P Max 2 sprays? 14 Aza naphthalenes Nimrod bupirimate ASP Max 3 sprays 1 Hydroxylpyrimidine Amistar azoxystrobin P Max 4 sprays 7 QoI Karma potassium bicarbonate AS Max 8 sprays 1 Inorganic AS Max total dose of 60 kg/ha? Inorganic Stroby Kresoxim-methyl P Max 3 sprays 14 QoI Takumi cyflufenamid P Max 2 sprays 3 Phenylacetamide Kumulus sulphur P No limit 0 inorganic Topas penconazole ASP Max 4 sprays 3 DMI Talius proquinazid P 1 3 Azanaphthalenes % Maximum number of sprays Product type Not specified BCA 12 BCA 5 at 28 day intervals. Last spray no later than one month before end of cycle 2-6 at day intervals Plant strengthener Nutrient Powdery mildew 2017 Management criteria Criteria for management decisions on powdery mildew control Item How determined Risk Management options Disease risk Determined from input of More than 4 days with temperature and humidity risk above 10% data from logger in tunnel requires action to disease risk model and forward weather forecast from internet. Growth stage and rate of growth Mildew monitoring Inspections 1-2 times per week Product choice Fungicide (AS or ASP), BCA Spray interval 7 or 14 days Rapid leaf production, start of flowering Tunnel ventilation fruiting indicates increased risk and possible change of product Inspections 1-2 times per Scored 0-5, where week on youngest leaves 0=no mildew on 5 plants per plot. Plants will be selected at random for each inspection

8 Powdery mildew 2017 Weather risks Powdery mildew 2017 Programmes applied Date 10 Jul 17 Jul 24 Jul 31 Jul 7 Aug 14 Aug 21 Aug 28 Aug 4 Sep 11 Sep T T2 Systhane Nimrod Nimrod Topas Luna Topas + Luna Nimrod Takumi + Topas Sensation Frupica Switch Frupica Sensation + Scala Switch Scala Frupica Luna Luna T3 T4 T5 Sensation Switch + B204 Frupica Luna Switch Sensation + + Sirius Sirius Luna Frupica Sensation Switch Frupica + B204 Frupica Frupica Switch Switch + Sirius Switch Sensation Scala Luna Scala Sensation + Sirius Luna Sensation Scala + B204 Scala Scala + Sirius Scala Low incidence mildew in flowers + high risk Unidentifi ed fungus infecting flowers Powdery mildew 2017 Flower fungus

9 Powdery mildew 2017 Results Leaf mildew Powdery mildew 2017 Results Fruit mildew % Mildewed fruit at harvest on Strawberry cv. Amesti following treatment with 4 different programmes compared to an untreated control in 2017 % Mildewed fruit Untreated Fungicide only B204 + BCA Sirius + BCA BCA only 28/07/ /08/ /08/ /08/ /08/ /09/ /09/ /09/ /09/2017 Date assessed Powdery mildew Yield Fruit yield kg per plot over 14 harvests on Strawberry cv. Amesti following treatment with 4 different programmes compared to an untreated control in /07/ /08/ /08/ /08/ /08/ /09/ /09/ /09/ /09/2017 % Fruit yield kg per plot Untreated Fungicide only B204 + BCA Sirius + BCA BCA only Date assessed

10 Powdery mildew 2017 Data summary Treatment Programme Mean leaf % area mildewed Mean % mildewed fruit Total yield per plot kg 1 Untreated * 2 Fungicide only B Sirius BCA only * Most fruit from untreated plot was unmarketable Powdery mildew Conclusions Mildew model showed powdery mildew was a high risk throughout trial period Despite this mildew development on leaves was very low on untreated plots (7% leaf area mildewed) typical of Amesti. All programmes gave almost complete control of mildew By contrast mildew on fruit after 3 picks rose rapidly to 90%+. On treated plots fruit mildew did not rise above 3% with programmes based on BCAs performing as well as standard fungicide programme As mildew on leaves and fruit remained very low there only one occasion where intervention with fungicide was needed ACKNOWLEDGEMENTS Thanks to AHDB for funding Project SF157 Berry Gardens and Clockhouse Farms for providing the Amesti plants and bags Trials team at NIAB-EMR for applying the sprays Gloria Endredi, Tom Passey, Joyce Robinson, Jennifer Kingsnorth for assistance with the trials