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Management of Resistance to Imidacloprid
in Colorado Potato Beetles
in the Northeastern U.S.
Galen P. Dively
Department of Entomology
University of Maryland
College Park, MD 20742
Email: galen@umd.edu
Potential to develop resistance quickly
Pre-adaptation to toxic plant chemicals
High population density
High reproductive rate
Narrow host range - only solanaceous plants
Low gene flow - inbreeding
Neonicotinoid Insecticides
imidacloprid (Admire, Provado, Gaucho, Leverage, Genesis)
thiamethoxam (Platinum, Actara, Cruiser)
acetamiprid (Assail)
dinotefuran (Venom)
clothianidin (Poncho*)
thiacloprid (Calypso*) *not registered yet
Used extensively since 1995
All active on CPB; potential cross resistance
Baseline and Resistance Monitoring Program for CPB
Supported by Bayer CropSciences, Dow AgroSciences, and BASF
Baseline susceptibility levels to imidacloprid.
158 populations assayed during 1995-98 from potato
productions areas in the U.S., Canada, and Europe.
Follow-up monitoring to detect shifts in susceptibility.
167 populations assayed during 2001, 2003-06, many from
farms reporting reduced field performance of imidacloprid
Bioassays to examine cross-resistance relationships.
60 and 82 populations tested for thiamethoxam and spinosad
susceptibility, respectively.
Beetles collected by University cooperators and industry field personnel.
Field history information provided by grower questionnaire.
Reared in field or lab cages on potato plants.
Eggs collected and hatched to provide neonates for bioassays.
Susceptibility determined by exposing first instar larvae to a
potato-based agar diet.
Neonates are fed for 5 hr before exposure.
Full series of insecticide concentrations.
120-150 larvae are tested per concentration.
Mortality recorded after 48 hrs.
Concentration-mortality responses
and LC50 determined by probit analysis.
NJ reference colony used as a
reference population.
20 05 Bio a ssa y Re su lts f o r I mid a c lo p rid
Reported fi el d control Good Fai r Poor N ot used
16 32 populations
I mid ac lo p rid C50 (p p m)
0.28 to 17.6 ppm
12
L
8
4
0
MB
MD
MD
MD
MI
MI
ME
ME
ME
ME
ME
ME
ME
ME
ME
ME
ME
WI
DE
DE
DE
DE
PEI
VA
VA
VA
VA
ID
ID
MN
MN
NJ
NJ
NB
WA
ON
QU
NY
ND
F y
arm l ocati on b state
10 0
90
80
P e rce n t mo rtality
70
LC 5 0= 0. 4 ppm
60 Ba se lin e
50 Go o d e f f ic a c y
F a ir e f f ic a c y
40
P o o r e f f ic a c y
30
20
10
0
0.1 1 10 10 0 10 0 0
L o g c o n c e n tra tio n o f imida c lo p rid (p p m)
20 05 Bio a ssa y Re su lts f o r Th ia me th o x a m
Reported fi el d control Good Fai r Poor N ot used
2. 0
25 populations
Th iame th o xam LC50 (p p m)
0.13 to 1.76 ppm
1. 5
1. 0
0. 5
0. 0 MB
MD
MD
MD
ME
MI
ME
DE
DE
DE
PEI
VA
VA
VA
VA
ID
ID
MN
MN
NJ
NB
ON
QU
NY
ND
F y
arm l ocati on b state
Re la tio n sh ip b e twe e n I mid a c lo p rid a n d Th ia me th o x a m Re sp o n se s (2
T h i o me th o x a m c o n tro l h i sto ryood
G Fai r Poor N ot used
2. 0
1. 8 p
r = 0.78, < 0.001
Thia metho xa m LC50 (pp m)
1. 6
1. 4
1. 2
1. 0
0. 8
0. 6
0. 4
0. 2
0. 0
0 2 4 6 8 10 12
I mida c lo p rid L C (p p m)
50
Re la tio n sh ip b e twe e n I mid a c lo p rid a n d Ac e ta mip rid Re sp o n se s (2
I mid a c lo p rid c o n tro l h isto ry Su sc e p tib l e R e sista n t
4
Ac eta mip r id LC50 (pp m)
3
2
1
Popul ati ons were never exposed to acetam i pri d
0
0 2 4 6 8 10 12
I mida c lo p rid L C (p p m)
50
Re la tio n sh ip b e twe e n I mid a c lo p rid a n d Sp in o sa d Re sp o n se s (2 0 0
Sp in o sa d c o n tro l h isto ry Go o d F a ir No t u se d
7
p
r = 0.43, = 0.049
6
Spin o s a d LC (pp m)
5
50
4
3
2
1
0
0 2 4 6 8 10 12
I mida c lo p rid L C (p p m)
50
Conclusions from Baseline and Resistance Monitoring Work
CPB has developed significant resistance to imidacloprid since its introduction
and field control failures are becoming commonplace.
Resistance management practices have slowed the rate of resistance in certain
areas.
Baseline susceptibility to imidacloprid has not changed significantly in potato
production areas with low population pressure.
Thiamethoxam and acetamiprid are cross-resistant to imidacloprid, thus
switching to these neonicotinoids will not help to slow resistance.
Several farms have reported fair to poor control with thiamethoxam and
bioassay results confirm detectable shifts in susceptibility.
No consistent positive association between levels of susceptibility to spinosad
and imidacloprid. Most growers still report good field efficacy with spinosad on
farms where it has been previously used.
Low variation in dose-mortality responses to metaflumizone.
Most populations are still susceptible to neonicotinoids.
Most likely to lead to resistance to neonicotinoids
Admire, Platinum or Venom (or seed piece treatments) at planting,
L followed by foliar sprays of Provado, Actara, Assail, Venom or
L
e Leverage
e
s s
No in-furrow treatment; multiple sprays of Provado, Actara,
s Assail, Venom or Leverage with minimal adherence to thresholds s
R Admire, Platinum or Venom (or seed piece treatments) at
planting, followed by foliar sprays of different modes of action S
o c
t o
a Admire, Platinum or Venom applied as a perimeter treatment to u
t create a refuge, followed by prescribed sprays of different
modes of action (Alverde, Spintor, Agri-Mek, Rimon, and cryolite )
t
i i
o n
n No in-furrow treatment; prescribed sprays of different modes of
action; switch to different class each generation or season g
Least likely to lead to resistance to neonicotinoids
Rotating away from last year’s potatoes slow the invasion
time, reduces population size, and increases chances of
gene mixing.
E FFE C T OF C R OP R OTA TION ON C P B A R R IV A L TIME
Surrounded by
fal l ow fi el ds
Surrounded by
wi nter wheat
Perimeter application of in-furrow treatments
Treated
Refuge
Recommended for rotated
fields
Can reduce control costs
by as much as 70%
Conserves susceptible
beetles
Scout Fields, Use Thresholds, and Rotate Insecticides
with Different Modes of Action
Alternative insecticides for CPB
control:
spinosad (SpinTor, Entrust)
indoxicarb (Avaunt)
abamectin (AgriMek)
novaluron (Rimon)
cryolite (Kryocide)
oxamyl (Vydate)
Expect registration of metaflumizone (Alverde) in early 2007.
Belongs in the semi-carbizone class of chemistry. Provide
excellent control of CPB.
Take-Home Message
Neonicotinoid insecticides are still the most effective and
reliable chemical option, but this may not be the case for very
long.
Must be deployed in a resistance management program that
includes other practices to minimize selection pressure.
Crop rotation, perimeter treatments, scouting and use of
treatment thresholds, rotation of modes of action
Plan crop and insecticide rotation schemes in cooperation with
neighboring potato growers to reduce population build-up of
resistant insects at the community level.
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