Achour Amiri, Philip F. Harmon, Natalia A. Peres

Winter BGA meeting, Plant City, FL, 02/20/14

Early signs of widespread fungicide resistance in Botrytis across blueberry

fields in central Florida

Abou

nd

Topsin-M

Gray mold management in strawberry

Widespread Resistance in FL Strawberry Fields13.5

86.5Pristine

Sensitive Resistant

14.6

85.4

Cabrio

47.352.7

Switch (Cyprodinil)

60

40

Elevate

5

95Topsin-M

100

Switch (fludioxonil)

Botrytis outbreak on strawberry in 2012

The many faces of Botrytis on blueberry

Leaf

Shoot blight Total blossom damage

Sporulation on a blossom

Shoot tip

Green and mature fruit

Gray mold management in blueberry

Trade name Active ingredient Efficacy* Resistance Risk

Cabrio Pyraclostrobin + (curative ?) ++++

Pristine Pyraclostrobin + Boscalid ++ ++++

Fontelis** Penthiopyrad +++ +++

Elevate/Captevate Fenhexamid +++ +++

Switch Fludioxonil+cyprodinil ++++ +/+++

Captan/Captec Captan ++ (Protectant)

?

* Efficacy will depend on frequency and distribution of resistant population** Labeled for lowbush blueberry

Survey of fungicide sensitivity in Botrytis in Central- FL

10 locations surveyed in 2013 (March-May)

2 in Polk County 3 in Citrus County 5 in Hillsborough County

Total number of isolates: 192

Sensitivity to 9 fungicides from different chemical groups

Fungicide sensitivity in Botrytis in Central- FL

* The other active ingredient of Pristine

Switch

Is population shift between crops a potential source of resistance in blueberry?

?

Labeled in strawberrynot in blueberry

From the same chemical group

New, potentially effective

* Labeled for lowbush blueberry** Not registered yet

Some variability but resistance is spread across locations

a Number of isolates from each field* Both active ingredients of Switch

Location County n a Cabrio Pristine Elevate Cyprodinil* Fludioxonil*1 Polk 15 100.0 73.3 40.0 40.0 0.02 Polk 10 90.0 10.0 40.0 40.0 0.03 Citrus 15 100.0 80.0 20.0 60.0 0.04 Citrus 20 85.0 30.0 45.0 30.0 0.05 Citrus 40 85.0 52.5 52.5 42.5 0.06 Hillsborough 20 100.0 65.0 85.0 60.0 0.07 Hillsborough 10 90.0 60.0 10.0 20.0 0.08 Hillsborough 15 86.7 33.3 20.0 60.0 13.39 Hillsborough 19 64.4 42.1 21.1 31.6 0.0

10 Hillsborough 28 100.0 78.6 71.4 60.7 0.0

Resistance frequency (%)

Management at risk because of multiple resistance

MFR2 2 fungicidesMFR3 3 “MFR4 4 “MFR5 5 “MFR6 6 “MFR7 7 “

Phenotype Resistant to

MFR = The same isolate may be resistant to 2, 3, 4 or more fungicides, simultaneously.

Best management practices Spray when the plant is most susceptible:

Flowering

and

When weather conditions are conducive: Temperature (~68°F) and wetness (10 to 14h)

Is reducing number of sprays the solution?

Citrus County: Floral City

Polk County: Lake Alfred

Hillsborough County:DoverPlant CityBalm

Locations of weather stations

Reducing sprays doesn’t seem to affect control efficacy

Calendar = Weekly applicationAlert = Spray only when conditions are conducive to Botrytis

2011-2012 Strawberry season

17* 9

* Number of fungicide applications/season

168

21

11

15 10

Spray at appropriate timing and growth stage

Low Botrytis Risk: spray Captan

Moderate Botrytis risk: spray Elevate, Pristine, Fontelis (lowbush)

High Botrytis risk: spray Switch

Preferably within the 24 hours following the alert

http://www.agroclimate.org/tools/strawberry/

Monitoring weather conditions, sign up, alerts:

Additional management recommendations

https://edis.ifas.ufl.edu/hs380

Perspective

Conduct additional resistance monitorings across the State: Please contact us

Develop efficient rotation programs

Investigate the impact of different sources of botrytis inoculum

Acknowledgements

Participating growers Mr. Gary K. England Strawberry pathology lab team

Contact Information:

Dr. Achour AmiriGulf Coast Research and Education Center14625 CR 672Wimauma, FL, 33598

Phone: 813-633-4153Email: aamiri@ufl.edu

Dr. Harmon and Dr. Peres