Early signs of widespread fungicide
resistance in Botrytis across blueberry
fields in central Florida
Achour Amiri, Philip F. Harmon, Natalia A. Peres
Winter BGA meeting, Plant City, FL, 02/20/14
Gray mold management in strawberry
Topsin-M
Widespread Resistance in FL Strawberry Fields
13.5
14.6
85.4
86.5
95
Topsin-M
Cabrio
Pristine
40
47.3
60
Elevate
5
100
52.7
Switch (Cyprodinil)
Sensitive
Switch (fludioxonil)
Resistant
Botrytis outbreak on strawberry in 2012
The many faces of Botrytis on blueberry
Shoot tip
Shoot blight
Total blossom damage
Sporulation on a blossom
Leaf
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
Switch
* The other active ingredient of Pristine
Is population shift between crops a potential source of resistance in blueberry?
?
Labeled in strawberry
not in blueberry
* Labeled for lowbush blueberry
** Not registered yet
New, potentially
effective
From the same chemical group
Some variability but resistance is spread across locations
Resistance frequency (%)
Location
1
2
3
4
5
6
7
8
9
10
a
County
Polk
Polk
Citrus
Citrus
Citrus
Hillsborough
Hillsborough
Hillsborough
Hillsborough
Hillsborough
a
n
15
10
15
20
40
20
10
15
19
28
Cabrio
100.0
90.0
100.0
85.0
85.0
100.0
90.0
86.7
64.4
100.0
Pristine
73.3
10.0
80.0
30.0
52.5
65.0
60.0
33.3
42.1
78.6
Number of isolates from each field
* Both active ingredients of Switch
Elevate
40.0
40.0
20.0
45.0
52.5
85.0
10.0
20.0
21.1
71.4
Cyprodinil*
40.0
40.0
60.0
30.0
42.5
60.0
20.0
60.0
31.6
60.7
Fludioxonil*
0.0
0.0
0.0
0.0
0.0
0.0
0.0
13.3
0.0
0.0
Management at risk because of multiple resistance
Phenotype Resistant to
MFR2
MFR3
MFR4
MFR5
MFR6
MFR7
2 fungicides
3
“
4
“
5
“
6
“
7
“
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?
Locations of weather stations
Citrus County: Floral City
Polk County: Lake Alfred
Hillsborough County:
Dover
Plant City
Balm
Reducing sprays doesn’t seem to affect control efficacy
2011-2012 Strawberry season
11
21
8
16
15
10
17* 9
* Number of fungicide applications/season
Calendar = Weekly application
Alert = Spray only when conditions are conducive to Botrytis
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
Monitoring weather conditions, sign up, alerts:
http://www.agroclimate.org/tools/strawberry/
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
Contact Information:
Dr. Achour Amiri
Gulf Coast Research and Education Center
14625 CR 672
Wimauma, FL, 33598
Phone: 813-633-4153
Email: aamiri@ufl.edu
Dr. Harmon and Dr. Peres
Participating growers
 Mr. Gary K. England
Strawberry pathology lab team