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Neonicotinoid InsecticidesUse Characteristics – and
Intersections with Pollinators
Whitney CranshawColorado State University
Outline
• Introduction – What is a Neonicotinoid?• Brief history of insecticides and the
place of Neonicotinoids• Characteristics and uses of the
Neonicotinoids• Honey bees and Neonicotinoids
– Possible effects– Routes of exposure
Outline
• Honey bees – what are the causes for impacting honey bee colony health?
• Minimizing hazards to pollinators from insecticide use
• Consumer messaging for protecting pollinators
Neonicotinoids• Insecticide class originally developed
commercially in the late 1980s• Mode of action - Nicotinic acetylcholine receptor
agonist• IRAC Mode of Action Group 7A• Nicotine mode of action similar
Neonicotinoids act on the cholinesterase receptors of the nicotinic acid pathway. This is similar to the mode of action of nicotine.
Neonicotinoids• Insecticide class originally developed commercially in the late 1980s• Mode of action - Nicotinic acetylcholine receptor agonist
• IRAC Mode of Action Group 7A• Nicotine mode of action similar
• First new class of insecticide with systemic activity in plants in 30+ years
• Low toxicity to vertebrates accelerated registration as “reduced risk” products
Primary Neonicotinoid Insecticides Used in the United States
• Imidacloprid (Admire, Provado, Merit, Marathon, Gaucho, etc.)
• Clothianidin (Clutch, Celero, Arena, Poncho)
• Thiamethoxam (Actara, Cruiser, Flagship, Meridian)
• Dinotefuran (Venom, Safari, Zylam)• Acetamiprid (Assail, Tristar)• Thiacloprid (Calypso)
Primary Neonicotinoid Insecticides Used in the United States
• Imidacloprid (Admire, Provado, Merit, Marathon, Gaucho, etc.)
• Clothianidin (Clutch, Celero, Arena, Poncho)• Thiamethoxam (Actara, Cruiser, Flagship, Meridian)
• Dinotefuran (Venom, Safari, Zylam)• Acetamiprid (Assail, Tristar)• Thiacloprid (Calypso)
Imidacloprid-containing Products
• Landscape Market– Merit, Criterion, Lesco Bandit, etc.
• Nursery Market– Marathon
• Agriculture Market– Admire, Provado, Gaucho
• Over-the-counter Market– Bayer, Bonide, fertilome – more to come
• Pet care Market– Advantage
Commercial formulation for
ornamentals
Commercial formulation for fruits and vegetables
Retail formulation
Acetamiprid formulations
Not all Neonicotinoids are alike:
• UV stability• Water solubility• Rate of uptake by plants• Mobilization within plants• Host range of susceptible
insects
Comparison of UV Stability
0
5
10
15
20
25
30
35
Hal
f life
(day
s)
Aquatic Photolysis
AcetamipridImidaclopridThiamethoxamDinotefuranClothianidin
Data obtained from published EPA registration documents
Slide Credit: R. Fletcher
UV Stability
Neonictoinoids are generally not UV stable. Foliar persistence can be shortened by this feature.
Acetamiprid isan exception.
Relative Water Solubility of Neonicotinoids:
Information sourcesClothianidin (Celero), Acetamiprid (Tristar), Dinotefuran (Safari) – EPA Pesticide Fact Sheet Imidacloprid (Marathon), hiamethoxam (Flagship) – MSDS for Products
Water Solubility (Active Ingredient)
327 5002950 4100
39830
0
10000
20000
30000
40000 Clothianidin
Imidacloprid
Acetam
iprid
Dinotefuran
Thiamethoxam
Slide information courtesy J. Chamberlin
Water SolubiilityThere is wide range of water solubility among the neonictoinoids.
Dinotefuran (Safari) is highly water soluble.
Koc Values of Neonicotinoids:
166
440
267245
260
Clothianidin
Imidacloprid
Acetam
iprid Dinotefuran
Thiamethoxam
Source Data: EPA Pesticide Fact Sheets
Koc ValueThere is wide range of Koc values (measure of adsorption to organic matter) among the neonicotinoids. This affects mobility within plants.
Dinotefuran (Safari) has a much lower Koc value than do other neonicotinoids
Some Generalizations…
Neonicotinoid Koc Water Solubility
Acetamiprid Medium High
Clothianidin Medium Low
Dinotefuran Low Very High
Imidacloprid High Low
Thiamethoxam Medium High
Some Generalizations…
Neonicotinoid A.I.
Relative Speed of Uptake
Relative Rate of Persistence
Acetamiprid Med. (?) – Fast Short – Mod. (?)
Clothianidin Slow (?) Mod. – Long (?)
Dinotefuran Fast Short – Mod (?)
Imidacloprid Slow (?) Long
Thiamethoxam Med(?) –Fast
Short – Mod. (?)
Why Use Neonicotinoids?
• Effectiveness against certain pests
• Systemic activity allows desirable application methods
• Relatively low hazard to applicator
Organophosphates• Primary class used during 1960s through
early 1990s– Identified incidental to discovery of chemical
warfare agents• Some have systemic activity• Persistence in environment: days to weeks
Neonicotinoids – and pyrethroids – have largely replaced the organophosphates for insect control
Organophosphates• Mode of Action: Inhibition of acetylcholinesterase
(IRAC class 1B)– Effects persist and can accumulate with repeated
exposure• Acute Toxicity to Humans: Moderate to very high
– Special concerns about exposure to young
Some Organophosphates Used Historically for Yard/Garden Use
• Acephate (Orthene)• Malathion• Diazinon• Chlorpyrifos (Dursban/Lorsban)• Dimethoate (Cygon)• Disulfoton (DiSyston)
Organophosphates• Non-target Effects:
– Birds – generally high to very high acute toxicity– Fish – moderate to high acute toxicity– Honey bees – high toxicity through contact
• Current Status– Steady restriction of registrations since late
1990s• Increased recognition of neurotoxic effects• Increased availability of alternatives
Some Mammalian LD50 (mg/kg –Oral route) Values
• Methyl parathion (OP)– 18-50
• Dimethoate (OP)– 60-387
• Carbofuran (C)– 4-35
• Carbaryl (C)– 250-850
• Bifenthrin (Py)– 54-70
• Permethrin (Py)– 340-3000
• Table Salt– 3000
• Acetamiprid (NN)– 330
• Imidacloprid (NN)– 450
• Chlothianidin (NN)– >500
• Thiamethoxam (NN)– > 5000
• Dinotefuran (NN)– >8000
• Ethyl alcohol– 7060
Distribution of C14 labeled Thiamethoxam™ 25WG after a foliar application to cucumber leaves
1 hour after application 24 hour after application8 hour after application
Slide Credit: N. Rechcigl
Systemic Insecticides• Capable of some translocation in plant• Range exists in ability to move in plant
– Limited to translaminar movement– Broadly distributes in plant (usually to newer
growth)• Systemic activity is limited to a small number
of insecticides– Some organophosphates and carbamates– Most neonicotinoids– Abamectin (translaminar only)
Not all Neonicotinoids are alike:
• UV stability• Water solubility• Rate of uptake by plants• Mobilization within plants• Host range of susceptible
insects
Acute Toxicity of Neonicotinoids to Adult Honey Bees
(Dermal LD50 in micrograms/bee)
• Acetamiprid 8.09• Imidacloprid 0.08• Dinotefuran 0.022• Thiamethoxam 0.024• Chlothianidin 0.044
Acute Toxicity of Neonicotinoids to Adult Honey Bees
(Oral LD50 – micrograms/bee)
• Acetamiprid 14.53• Imidacloprid 0.005• Dinotefuran 0.056• Thiamethoxam 0.005• Chlothianidin 0.0003
Soft Scales Armored (Hard) Scales
Effectiveness of neonicotinoid insecticides against scale insects varies by type of scale and mobility of the insecticide
Soft Scales Include:
Pine Tortoise Scale, Striped Pine Scale, European Elm Scale, Cottony Maple Scale
European elm scale produces large amounts of honeydew. Where it lands and persists, sooty molds grow.
Dinotefuran• Neonicotinoid insecticide• Primarily labeled to control insects
that suck sap (Order Hemiptera)– Aphids– Soft scales–Armored scales
• Has systemic activity in plants– Considerably more mobile in plant than
other neonicotinoids
Neonicotinoids vary in effectiveness against caterpillars.
Imidacloprid – poor
Dinotefuran – fair
Acetamiprid - good
Predators of spider mites include minute pirate bugs (left), predatory mites (below left) and predatory thrips (below)
Emerald Ash Borer EfficacySmitley, Davis, MSU, 2006
0
1
2
3
4
5
6
7
8
9
Larve/sqM
Control
Bayer Adv Drench Fall 05
Bayer granular Fall 05
Merit Drench Spring 06
Arena Drench Fall 05
Arena Drench Spring 06
Safari Implant
Conserve Drench Spring 06
Conserve Trunk 2x Spring 06
TriStar Inject Spring 06
TriStar Inject Spring 06East Lansing site, 2006
Slide Credit: R. Fletcher
Four Agrilus sp. borers found in Colorado
Top Row - Rose stem girdler (left), Bronze birch borer (right)
Bottom Row – Honeylocust borer (left), Gambeloak borer (right)
Emerald Ash Borer Control Options
• Soil applications with systemic insecticides– imidacloprid, dinotefuran
• Non-invasive trunk sprays of systemic insecticides– dinotefuran
• Trunk injections of systemic insecticides– Emamectin benzoate (TREE-Age),
azadirachtin (TreeAzin), imidacloprid
Target Life Stages for EAB Treatments
Adults as they feed on foliage
Young larvae that tunnel in the phloem and cambium
Emerald Ash Borer Insecticides
• Imidacloprid (Merit, Xytect, Criterion, etc.)– Soil drench, possible trunk injection
• Dinotefuran (Safari, Zylam, Transtect)– Basal trunk spray, possible soil drench
• Emamectin benzoate (TREE-Age)– Trunk injection only
• Azadirachtin (TreeAzin)– Trunk injection only
Neonicotinoid Insecticides for EAB Control
• Imidacloprid– Merit, Xytect, Criterion, Zenith, Bandit……
• 75WSP and 2F formulations– Several retail formulations now available
• Typically 1.47% liquid formulations
• Dinotefuran– Safari, Zylam, Transtect
Injections can be very useful to bypass mulch or fabric barriers
Injections also prevent the presence of surface residue of the applied insecticide
Soil applications of systemic insecticides should not be made if there are flowering plants at the application site
What rate of use for imidacloprid soil treatments?
• 1X rate = 1.4 grams active ingredient/inch trunk diameter
• Rates of use allowed in label directions– 75 WP formulation - 1X/application– 2F and 75WSP formulations - 1X up to 15
inches diameter; 2X in larger trees– Retail nursery formulations – 1/2X
• Limited to single application/year
1 ft.2 ft.
Area increases as the square of the width (diameter)
Example: A circle that is 2 ft. wide has an area 4X greater than a circle of 1 ft. diameter
Bottom line: Larger trees have proportionately much greater volume than do smaller trees. Insecticides used at rates based on DBH will be more diluted in larger trees.
Use of High or Low Rates of Imidacloprid?
Low Rates (1X, 1/2X)• Smaller trees• EAB populations
low, moderate• Spring
applications
High Rates (2X)• Large trees• High EAB
populations present (peak outbreak phase)
• Fall applications
Over-the-Counter Imidaclopridformulations have label use instructions that would allow EAB control only on small diameter trees
Conditions Optimizing Uptake and Distribution of Systemic Insecticides
• Soil is moist (but not saturated!)• Soil temperatures are above 450F• Ambient air temperatures are between
400-900F
In other words, conditions are most favorable to transpiration.
Fall Application vs. Spring ApplicationWhat are the Trade-offs with
Fall Applications vs. Spring Applications?
Take home message to me: Spring applications are more efficient in the use of soil applied imidacloprid than is a fall application to ash (a deciduous tree)
Another consideration with fall vs. spring applications of systemic insecticides?
Effects on potential residues present in nectar and pollen –residues much more likely if insecticides applied in fall
Is Ash Pollen from EAB Treated Trees a Threat to Bees?
Present evidence from the midwest suggests that ash pollen is collected infrequently and does not constitute a biologically significant source of possible neoniciotinoid exposure.
Willows
Maples, boxelder
Wind pollinated plants can be used as significant pollen sources by honey bees
Flowering ash (Fraxinus ornus), native to southern Europe, is an important pollen source for honey bees in Europe
Study in progressSurvey of pollen collected by honey bees
Question to answer: What are the important pollen sources used by honey bees in Colorado?
Soil Treatment Options for EAB
• Imidacloprid– Merit, Xytect, Criterion, Zenith, Bandit……
• 75WSP and 2F formulations– Several retail formulations now available
• Typically 1.47% liquid formulations
• Dinotefuran– Safari, Zylam, Transtect
Relative Water Solubility of Neonicotinoids:
Information sourcesClothianidin (Celero), Acetamiprid (Tristar), Dinotefuran (Safari) – EPA Pesticide Fact Sheet Imidacloprid (Marathon), hiamethoxam (Flagship) – MSDS for Products
Water Solubility (Active Ingredient)
327 5002950 4100
39830
0
10000
20000
30000
40000 Clothianidin
Imidacloprid
Acetam
iprid
Dinotefuran
Thiamethoxam
Slide information courtesy J. Chamberlin
Koc Values of Neonicotinoids:
166
440
267245
260
Clothianidin
Imidacloprid
Acetam
iprid Dinotefuran
Thiamethoxam
Source Data: EPA Pesticide Fact Sheets
Basal Trunk Sprays of Dinotefuran
• Enters tree through thin areas of bark• Can be expected to reach peak levels in
foliage in about 2-3 weeks• Adjuvant? – May help some to increase
deposition into trunk fissures, slow drying
Whole tree sprays produce surface residues on all foliage. Natural enemies are killed. Natural controls are wasted.
Treatment area limited to bark of lower trunk. Impacts on natural enemies is minimalized
Relative Water Solubility of Neonicotinoids:
Information sourcesClothianidin (Celero), Acetamiprid (Tristar), Dinotefuran (Safari) – EPA Pesticide Fact Sheet Imidacloprid (Marathon), hiamethoxam (Flagship) – MSDS for Products
Water Solubility (Active Ingredient)
327 5002950 4100
39830
0
10000
20000
30000
40000 Clothianidin
Imidacloprid
Acetam
iprid
Dinotefuran
Thiamethoxam
Slide information courtesy J. Chamberlin
Dinotefuran Trunk SpraysAdvantages
• Ease of application• Does not require
tree wounding• Rapid uptake
following application
• Applied after bloom (of ash)
Disadvantages• Requires annual
application• Use likely limited to
trees without thick bark
• Higher cost• High leaching
potential if put into soil
Potential of dinotefuran trunk sprays used on ash to affect pollinators
Applications made after flowering. Persistence is short (months). Potential of residues in pollen lower than all other EAB treatments.
Recent Developments Affecting Neonicotinoids and Pollinators
• Description of several new sublethal effects of neonicotinoids on honey bees– Deleterious behaviors– Effects on susceptibility to other stressors
• Studies showing presence of neonicotinoids in plants is more widespread than previously known– Agricultural uses as seed treatment primarily– Chlothianidin mostly involved
• Better understanding that some insecticide is translocated into pollen and nectar
Possible Sublethal Effect of Pesticides on Honey Bee Behaviors
• Effects on activity (agitation, lassitude)• Effects on memory of foraged sources• Decision making when tasking• Increased susceptibility to pathogens
Note: These were experimental studies showing potential effects when exposure levels were sustained at high levels (>10 ppb).
2013 Oregon Bumble Bee Kills
Involved use of dinotefuran, applied shortly before bloom. Treatment timing produced high residues during bloom.
Soil Applied Systemic Insecticides and Honey Bees – Targets for Concern
• Plant is visited heavily by honey bees
• Plant is treated with persisting systemic insecticides for some pest insect
• Treatments are applied before bloom
Top honey bee-visited plants include: most Sedums, most thistles, catmint, Gaillardia, most Agastache, Blue mist spirea, Russian sage, fruit trees, linden, golden raintree ……..
Neonicotinoids and Pollinators: Bottom Line
Avoid applications to plants that bees visit that are in bloom – or soon will be in bloom
Soil Applied Systemic Insecticides and Honey Bees – My Concern
• Plant is visited heavily by honey bees
• Plant is common in a location so many honey bees are visiting it
• Plant is treated often with soil applied systemic insecticides for some pest insect
Top honey bee-visited plants include: most Sedums, most thistles, catmint, Gaillardia, most Agastache, Blue mist spirea, Russian sage, fruit trees, linden, golden raintree ……..
Recent EPA Statements on Neonicotinoids and Honey Bees
• Development of newer methods to assess hazard to honey bees is needed
• Presently known information of hazard to honey bees does not reach threshold for withdrawal of registration withdrawals
• Accelerated reevaluation of neonicotinoid risks in progress
Recent EPA Statements on Neonicotinoids and Honey Bees
• Development of newer methods to assess hazard to honey bees is needed
• Presently known information of hazard to honey bees does not reach threshold for withdrawal of registrations
• Accelerated reevaluation of neonicotinoid risks in progress
Recent EPA Statements on Neonicotinoids and Honey Bees
• Development of newer methods to assess hazard to honey bees is needed
• Presently known information of hazard to honey bees does not reach threshold for withdrawal of registration
• Accelerated reevaluation of neonicotinoid risks in progress
Recent EPA Statements on Neonicotinoids and Honey Bees
• Development of newer methods to assess hazard to honey bees is needed
• Presently known information of hazard to honey bees does not reach threshold for withdrawal of registration withdrawals
• Accelerated reevaluation of neonicotinoid risks in progress
What Pesticides are Found associated with Honey Bees?
Agriculture applications vs. Beekeeper applications
Maximum Pesticide Residues Found in Pollen (parts per billion)
• Fluvalinate 2670• Coumaphos 5828• Chlorthalonil 98,900• Pyrethrins 62• Malathion 61• Methyl parathion
26,000
• Carbaryl 94,000• Permethrin 92• Esfenvalerate 60• Bifenthrin 13• Imidacloprid 912• Thiamethoxam 53
Fluvalinate and coumaphos are insecticides used in the hive by beekeepers to control pests of honey bees
Maximum Pesticide Residues Found in Honey (parts per billion)
• Fluvalinate 750• Coumaphos 2020• Chlorothalonil 10• Pyrethrins ND• Malathion 243• Methyl parathion 50
• Carbaryl 42• Permethrin 11• Esfenvalerate >1• Bifenthrin 3• Imidacloprid 29• Thiamethoxam ND
Maximum Pesticide Residues Found in Wax (parts per billion)
• Fluvalinate 204,000• Coumaphos 94,131• Chlorthalonil 53,700• Pyrethrins 237,000• Malathion 6,000• Methyl parathion
3085
• Carbaryl 820• Permethrin 372• Esfenvalerate 56• Bifenthrin 56• Imidacloprid 14• Thiamethoxam N.D.
Contributors in Declines of Honey Bees in North America
What Honey Bee Health Researchers are Saying• Varroa mite
– Sublethal effects from in-hive varroa mite treatments
• Extremely narrow genetic base of NA honey bees• New viruses (many vectored by Varroa mite)• Nosema ceranae, other new pests• Changes in symbionts/microbes from use of antibiotics by
beekeepers • Effects of fungicides on symbionts that contribute to food
utilization/immune response; synergizm of fungicides with insecticides possible
• Periodic movement and concentration of honey bees for crop pollination which allows transfer of pathogens
• Possibly some insecticides being used in agriculture, including neonicotinoids
Varroa mite transferred from an Asian giant bee (Apis cerana) to honey bee in the past few decades.
The worst day in the history of the honey bee
Contributors in Declines of Honey Bees in North America
What Honey Bee Health Researchers are Saying• Varroa mite
– Sublethal effects from in-hive varroa mite treatments
• Extremely narrow genetic base of NA honey bees• New viruses (many vectored by Varroa mite)• Nosema ceranae, other new pests• Changes in symbionts/microbes from use of antibiotics by
beekeepers • Effects of fungicides on symbionts that contribute to food
utilization/immune response; synergism of fungicides with insecticides possible
• Periodic movement and concentration of honey bees for crop pollination which allows transfer of pathogens
• Possibly some insecticides being used in agriculture, including neonicotinoids
Contributors in Declines of Honey Bees in North America
• Transfer of the Varroa mite from Apiscerana to Apis mellifera – and subsequent spread to North America
• A very narrow genetic base of honey bees through inbreeding that has resulted in extremely deficient capabilities to handle environmental toxins
Contributors in Declines of Honey Bees in North America
• Varroa mite• Poor genetics• Several new viruses, many vectored by
varroa mite– Deformed wing virus, Acute bee paralysis
virus, Israeli acute bee paralysis virus……. • Other pathogens/pests that have recently
been established in North America– Nosema ceranae, small hive beetle……
Contributors in Declines of Honey Bees in North America
• Varroa mite• Poor genetics• New viruses• Nosema ceranae, other new pests• Sublethal effects of pesticides applied to
control Varroa mites• Changes in symbionts/microbes beneficial
to honey bee health that are disrupted by antibiotics (and maybe fungicides)
Contributors in Declines of Honey Bees in North America
• Varroa mite• Poor genetics• New viruses• Nosema ceranae, other new pests• Sublethal effects of pesticides applied to
control Varroa mites• Changes in symbionts/microbes beneficial
to honey bee health that are disrupted by antibiotics (and maybe fungicides)
Contributors in Declines of Honey Bees in North America
• Varroa mite• Poor genetics• New viruses• Nosema ceranae, other new pests• Varroa mite pesticides• Changes in symbionts/microbes from use of antibiotics
and fungicides
• Periodic concentration of NA honey bees for certain pollination needs (e.g., almonds)
Contributors in Declines of Honey Bees in North America
• Varroa mite• Poor genetics• New viruses• Nosema ceranae, other new pests• Varroa mite pesticides• Changes in symbionts/microbes • Periodic movement and concentration of
honey bees • Possibly some insecticides being used in agriculture,
including neonicotinoids
Take Action to Protect Pollinators
• Prevent pesticide uses that pose significant risks to pollinators– Avoid uses on high risk plants– Avoid uses that allow exposure of pollinators
to pesticides• Promote practices that improve habitat for
pollinators– Improve food resources– Improve nesting habitat (solitary bees)
Neonicotinoids and Pollinators: Primary Precaution
Avoid applications to plants that are in bloom – or soon (weeks, months?) will be in bloom
Top honey bee-visited plants include: most Sedums, most thistles, catmint, Gaillardia, most Agastache, Blue mist spirea, Russian sage, fruit trees, linden, golden raintree ……..
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