Management of Resistance to Imidacloprid

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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_at_umd.edu
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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

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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
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• 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.

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• 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.

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• Mortality recorded after 48 hrs.
• Concentration-mortality responses and LC50
  determined by probit analysis.
• NJ reference colony used as a reference
  population.

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32 populations 0.28 to 17.6 ppm
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25 populations 0.13 to 1.76 ppm
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• 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.

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Most likely to lead to resistance to
neonicotinoids
Admire, Platinum or Venom (or seed piece
treatments) at planting, followed by foliar
sprays of Provado, Actara, Assail, Venom or
Leverage
Less Rotation
Less Scouting
No in-furrow treatment multiple sprays of
Provado, Actara, Assail, Venom or Leverage with
minimal adherence to thresholds
Admire, Platinum or Venom (or seed piece
treatments) at planting, followed by foliar
sprays of different modes of action
Admire, Platinum or Venom applied as a perimeter
treatment to create a refuge, followed by
prescribed sprays of different modes of action
(Alverde, Spintor, Agri-Mek, Rimon, and cryolite )
No in-furrow treatment prescribed sprays of
different modes of action switch to different
class each generation or season
Least likely to lead to resistance to
neonicotinoids
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Rotating away from last years potatoes slow the
invasion time, reduces population size, and
increases chances of gene mixing.
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Perimeter application of in-furrow treatments
Treated
Refuge
Recommended for rotated fields Can reduce control
costs by as much as 70 Conserves susceptible
beetles
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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.
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• 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.