Insecticide Resistance Action Committee
Understanding Insecticide Mode of Action
in Crop Protection Strategies
Caydee Savinelli
Annual Crop Protection School, 2015
ClickInsect
to edit Resistance
Master title style
• Experts estimate that there are over 500
species of insects and mites known to be
resistant to at least one class of pesticide.
• Every major agricultural crop and
ornamental has one or more resistant
pests.
• In addition to synthetic chemicals, pests
can develop resistance to insecticidal
soaps, B.t. and even pheromone disruption.
2
ClickResistance
to edit Master
title style
Insect
Mechanisms
• Target Site Resistance
 The target site is where the insecticide acts in the
insect.
 May be genetically modified to prevent the insecticide
binding or interacting at its site of action – reduces the
effect of the insecticide.
• Metabolic Resistance
 Metabolic resistance is the most common mechanism.
 Resistant insects may detoxify or destroy the toxin faster
than susceptible insects, or quickly rid their bodies of
the toxic molecules.
 Insects use their internal enzyme systems to break down
insecticides.

Resistant strains may possess higher levels or more
efficient forms of these enzymes.
3
ClickResistance
to edit Master
title style
Insect
Mechanisms
• Penetration Resistance
 Outer cuticle of the insect slows the absorption of
a broad range of chemicals.
 Penetration resistance is often present along with
other forms of resistance.
• Behavioral Resistance
 Resistant insects may detect or recognize a danger
and avoid the toxin.
 This mechanism of resistance has been reported
for several classes of insecticides, including
organochlorines, organophosphates, carbamates
and pyrethroids.
4
to editofMaster
title style
What isClick
the level
arthropod
resistance?
• Over 550 species of arthropods are resistant to pesticides
 88% insects, 12% mites
• Most of those insects come from 4 groups:
 Coleoptera (Beetles)
 Diptera (Flies)
 Hemiptera (Sucking Bugs)
 Lepidoptera (Moths & Butterflies)
• 60%+ of all resistant arthropods are agricultural pests
• Rest are:
 animal health (ticks and lice)
 public health (flies, mosquitoes, cockroaches)
 stored product pests (grain beetles)
 non-target organisms (predatory mites)
Source: Arthropod Pesticide Resistance Database – Michigan State University
Click to
edit Master
title style
Leading Global
Resistant
Agricultural
Arthropods
Common Name
Species
Order
No. active
ingredients
Two Spotted Spider Mite
Tetranychus urticae
Acari
79
Diamondback Moth
Plutella xylostella
Lepidoptera
76
Green Peach Aphid
Myzus persicae
Hemiptera
68
Colorado Potato Beetle
Leptinotarsa decemlineata
Coleoptera
48
Silverleaf Whitefly
Bemisia tabaci
Hemiptera
39
European Red Mite
Panonychus ulmi
Acari
38
Cotton Aphid
Aphis gossypii
Hemiptera
37
Cotton Bollworm
Helicoverpa armigera
Lepidoptera
33
Tobacco Budworm
Heliothis virescens
Lepidoptera
33
Egyptian Cotton Leafworm
Spodoptera littoralis
Lepidoptera
30
Source: Arthropod Pesticide Resistance Database – Michigan State University
Does insecticide
resistance
mean
the total
Click to edit
Master title
style
loss of insecticides?
• With current agricultural practices, the development of
insecticide resistance is inevitable.
• However, even though there is resistance, this does not mean
the insecticide is no longer effective.
• With crop protection insecticides, it is possible to manage
resistance and maintain susceptibility.
Organophosphates
Introduced
Pyrethroids
Introduced
Neonicotinoids
Introduced
7
to edit
Master
title
Are someClick
insects
more
prone
tostyle
resistance ?
• Common claim that some insects are more prone to resistance
development than others.
• Exposure to insecticide is key factor.
• Some insects, do appear to develop resistance faster than other
species, even if insecticide exposure is the same.
8
Click at
to edit
titleresistance?
style
Are mites
highMaster
risk for
• 20 acaricide modes of action (MoAs)
• Two spotted spider mite (Tetranychus urticae) has developed
resistance mechanisms against 17 MoAs
• Many populations have resistance to multiple MoAs
• Resistance develops rapidly in green houses
 Closed environment (limited gene flow)
 All year production
 High value crops – low tolerance of pest
 Mites - High fecundity, Short generation time
• Resistance in field crops generally slower
9
IRM
Implementation
Click
to edit
Master title style
Key Groups
IRAC
Industry
Insecticides or
Traits
University
EPA
10
Insecticide
Click to Resistance
edit Master Management
title style
IRAC’s Role
• IRAC-US is a task force affiliated to CropLife America.
 IRAC is comprised of scientists representing many companies which
develop and market agricultural chemicals
 Allows companies to effectively pool resources on IRM-related
issues; especially, with related chemistries or traits.
 Individual companies do not have the resources to carry out all
aspects of IRM - Collecting & Monitoring
• Gains alignment on IRM recommendations and educational
messages
• Serves as a coordinating group for outlining methodologies for
resistance surveys
• Provides funding to address emerging resistance issues
 i.e. – Soybean looper
Click to edit
Master title style
IRAC Website
- www.irac-online.org
Insecticide
Click to Resistance
edit Master Management
title style
Industry View
• Resistance, real or perceived, can greatly diminish the
value of products in the marketplace
 Increase in number & frequency of applications
 Product non-performance complaints go up and farmer
confidence goes down
• Resistance reduces the effective life of a product
 Shorter product life will lower the return on investment
 With discovery and registration costs of $200-350 million and
development timelines of 8-15 years, it is important to maintain
the current products in the market.
• Resistance management is an important component of
product stewardship
13
Insecticide
Click to Resistance
edit Master Management
title style
Industry’s Role
• Expertise
 Research & Development, Registration, Product Stewardship
• Interactions
 RACS, Universities, Consultants, IPM Centers, Customers
• Labels
 Mode of Action Labeling
 Effective rates and use patterns to minimize selection pressure
 Resistance Management Guidance
Clickof
to Action
edit Master
title style
Mode
Classification
• All products have been assigned to groups based on their
mode of action:
 i.e. pyrethroids are Group 3; Neonicotinoids are Group 4A,
Spinosad is Group 5, Diamides are Group 28
• Product labels include the number corresponding to the
mode of action group.
• The aim is to help product users make better decisions
such as product rotations or tank mixing.
IRAC - Insecticide Mode of Action Classification
Insecticide Resistance
ActionMaster
Committee
Click
to edit
title style
www.irac-online.org
Growth & Development Targets
 Group 7 - Juvenile hormone mimics
 Group 10 - Mite growth inhibitors
 Group 15 - Inhibitors of chitin biosynthesis
 Group 16 - Inhibitors of chitin biosynthesis
 Group 17 - Molting disruptor
 Group 18 - Ecdysone agonists / molting disruptors
Nerve & Muscle Targets
 Group 1 - Acetylcholinesterase (AChE) inhibitors 1A Carbamates, 1B Organophosphates
Respiration Targets
 Group 12 - Inhibitors of mitochondrial ATP
synthesis
 Group 13 - Uncouplers of oxidative
phosphorylation
 Group 20 - Mitochondrial complex III electron
transport inhibitors
 Group 21 - Mitochondrial complex I electron
transport inhibitors
 Group 23 - Inhibitors of acetyl CoA
carboxylase
 Group 25 - Mitochondrial complex II electron
transport inhibitors
 Group 2 - GABA-gated chloride channel antagonists 2A Cyclodiene Organochlorines, 2B Phenylpyrazoles
 Group 3 - Sodium channel modulators
3A Pyrethrins, Pyrethroids
 Group 4 - Acetylcholine receptor (nAChR) agonists
4A Neonicotinoids, 4C Sulfoxaflor, 4D Flupyradifurone
 Group 5 - Nicotinic acetylcholine receptor channel agonists Spinosyns
 Group 6 - Chloride channel activators - Avermectins
 Group 9 - Modulators of Chordotonal Organs
 Group 14 - Nicotinic acetylcholine receptor channel blockers
 Group 19 - Octopamine receptor agonists
 Group 22 - Voltage dependent sodium channel blockers
 Group 28 - Ryanodine receptor modulators - Diamides
Midgut Targets
 Group 11 Microbial disruptors of insect midgut
membranes
11A Bacillus thuringiensis,
11B Bacillus sphaericus
IRAC-US
IRM Plan
Click to
edit Master
title style
Plant Protection Insecticides
• Determine insecticide mode of action.
• Establish the baseline susceptibility of key high-resistance-risk pests
prior to and/or in the early years of commercialization.
• Include mode of action group on product labels.
• Provide resistance management recommendations on product labels.
• Encourage use of Integrated Pest Management (IPM) practices by
growers.
• Develop educational literature for growers, researchers and
extension agents to increase resistance management awareness,
particularly at the grower level.
• Monitor product performance over a wide range of geographies and
observe or track changes in the susceptibility of pest populations
over time.
17
Click to edit
Master title
style
Insecticide
Mixture
Statement
Click to edit
Master title
style
Insecticide
Mixture
Statement
• Insecticide Mixtures
 Mainly used for pest management
• Insecticide mixture considerations
 Active ingredients, use patterns, targeted pest complex.
• Mixtures of insecticides provide technical advantages for
controlling pests
 Increases level of target pest control
 Increases the spectrum
19
Click to edit
Master title
style
Insecticide
Mixture
Statement
• All of the following should be considered when using
mixtures for IRM:
 Individual insecticides in mixtures should be highly
effective & applied at effective rates.
 Mixtures with components having the same IRAC mode
of action classification are not recommended for IRM.
 When using mixtures, consider cross-resistance issues
between the individual components for the targeted
pest/s.
20
Insecticide
Click to Resistance
edit Master Management
title style
EPA’s Role
• For conventional pesticides, EPA has historically relied on voluntary
measures to encourage proactive resistance management by
pesticide users.
• Agency-approved labels are an important tool, but resistance
management labeling is voluntary (not mandatory for registrants).
• Bt Plant-Incorporated Protectants (PIPs) – a special case:
 EPA places a high value on preserving the significant agricultural and
environmental benefits of Bt PIPs
 EPA requires an Insect Resistance Management (IRM) plan for each registered
Bt crop.
• IRAC-US has provided a list of key pests with high potential for
resistance and an insecticide resistance management plan to EPA
21
Insecticide
Click to Resistance
edit Master Management
title style
University’s Role
• Lead or participate in the development of IRM plans
• Provide education and lead implementation of IRM
plans in respective geographies for the growers and
crop consultants.
• Monitor susceptibility of insects of concern.
• Provide feedback to companies on successes and
challenges with IRM plans.
22
Neonicotinoid
& Implementation
Click to IRM
editPlan
Master
title style
Bemisia tabaci – Arizona/California vs. Florida
Florida
• Single Host Crop
Arizona / California
• Multiple Host Crops
 Tomato
 Vegetables, Melons, Cotton
• Tomato Season - August
through May
• Crops grown throughout
the year.
23
Neonicotinoid
& Implementation
Click to IRM
editPlan
Master
title style
Bemisia tabaci – Arizona/California vs. Florida
• IRM Plan Development
 Led by university extension entomologists
 Team – Chemical Companies, Crop Consultants, Grower Groups,
Commodity Groups
• IRM Plan Implementation
 Newsletters
 Meetings
• Success Measurements
 Susceptibility monitoring
 Grower adoption surveys
24
Neonicotinoid
& Implementation
Click to IRM
editPlan
Master
title style
Bemisia tabaci – Arizona/California vs. Florida
AZ / CA Recommendations
FL Recommendations
• Guidelines based on the
cropping system
• Cultural Controls
 Crop Hygiene
 Tomato free period
• Neonicotinoids
 Application Method & Timing
• Neonicotinoid Uses
25
IRM Plan
& Implementation
Click
to edit
Master title style
Diamide Insecticides
• IRAC Diamide Working Groups
 Formed before registration of MOA
Group 28 products
 Global Alignment on IRM for Diamides
• Identified key insects of concern – U.S.
Insect
Scientific Name
Crop
Diamondback Moth
Plutella xylostella
Brassicas
Beet Armyworm
Spodoptera exigua
Vegetables
Codling Moth
Cydia pomonella
Pome Fruit
Colorado Potato Beetle
Leptinotarsa decemlineata
Potato
26
IRM Plan
& Implementation
Click
to edit
Master title style
Diamide Insecticides – IRAC-US Diamide WG
• Labels - MoA Symbol, Resistance Management Language
• Collaborate with University Research & Extension
 Develop best management guidelines for IRM
 Literature pieces
 Address emerging issues
27
Click to edit
Master title style
Summary
• Industry is motivated to have insect resistance
management as part of our product stewardship efforts in
order to protect the life of our products.
• IRAC is the industry task force used to create IRM
guidelines, educate and promote the value of insect
resistance management in crop production, ornamentals
and public health.
• In order for insect resistance management to be
successful, we need cooperation from all stakeholders!