Introduction to Pesticides:
Understanding Performance Characteristics of Insecticides
Insect
Plant
Chemistry
John C. Wise, Ph.D.
MSU Department of Entomology
Trevor Nichols Research Center
Toxicology 101
• Toxicology: The science of dealing with the dose and
antidotes of poisons
• Paracelsus (1492-1541) is the father of toxicology
– Formulated revolutionary views on toxicology
– Realized that poisons were chemicals, not “spirits”
• Toxicon = toxic agent = chemical agent
• Determined there were dose-response relationships
What makes something a poison?
"All substances are poisons; there
is none which is not a poison. The
right dose differentiates a
poison…."
Paracelsus
(1493-1541)
Which is a true example of a poisoning?
Woman Dies from
Drinking Water.
SACRAMENTO, California
(AP) — A woman in a radio
station’s contest to see how
much water she could drink
without going to the
bathroom died of water
intoxication, the coroner’s
office said Saturday.
44 Toxic Chemicals
Pollute Blood of
Canadians
Ottawa , Ontario - A cocktail of
harmful toxic chemicals has
been found inside every person
tested in a Canada-wide study,
released today by
Environmental Defense.
What is a Pesticide?
Historical definition:
“all inclusive word meaning killer of pests.”
- The ending “cide” comes from the latin “cida”
meaning killer.
Modern legal definition:
“any substance used for controlling, preventing,
destroying, repelling, or mitigating any pest.”
Pest Management
• To the degree that pest population
management and crop protection goals
are met, a compound’s performance
should be deemed acceptable.
• Crop protection does not necessitate
pest mortality!
The Only Good
Bug is a
Dead Bug !!!
What is Effective
Pest Management Performance?
“Any pest control tool (or combination
of tools) employed in an IPM program
must ultimately provide sufficient fruit
protection to meet minimum grade
standards for the targeted market.”
Insecticides Registered in Fruit Crops - 1996
Conventional Insecticides
New Insecticides
•
•
•
•
• Insect Growth Regulators (1)
• Avermectins (1)
• Neonicotinoids (1)
Chlorinated Hydrocarbons (1)
Organophosphates (6)
Carbamates (2)
Synthetic Pyrethroids (6)
Insecticides Registered in Fruit Crops - 2014
20th Century Insecticides
•
•
•
•
Chlorinated Hydrocarbons (1)
Organophosphates (2)
Carbamates (2)
Synthetic Pyrethroids (6)
21st Century Insecticides
•
•
•
•
•
•
•
•
•
•
•
Insect Growth Regulators (5)
Spinosyns (2)
Avermectins (2)
Neonicotinoids (5)
Oxadiazines (1)
Diamides (3)
Microbials/Botanicals (6+)
Particle Film (1)
Pyrizoles (1)
Pyridine Carboxamides (1)
Pre-mixes (4)
How are Pesticides Classified?
Pesticides are generally classified in 3 ways:
1. Based on chemical structures
2. According to their mode of action
3. According to their mode of entry
i.e.; ingestion, inhalation, contact absorption
“mode of action” refers to the mechanism by which an
insecticide controls the target organism.
Modes of Action of Major Synthetic Commercial Insecticides
Glutamate Receptor
Antagonists
Acetylcholinesterase Inhibitors
Acetylcholine
Receptor
Agonists
Sodium Channel
Agonists
Ecdysone
agonists
Uncouplers of
Mitochondrial Respiration
Pyrroles
GABA Receptor
Antagonists
Chitin synthesis
inhibitors
Pyrazoles
Avermectins
Carbamates
Organophosphates
Benzoylureas
Pyridazinones
dibenzoylhydrazines
DDT
Hydramethylnon
Spinosyns
Indoxacarb
Neo-nicotinoids
Cyclodienes
Pyrethroids
Phenylpyrazoles
Mode of Activity
“mode of activity” is the field-assessable symptoms of an
insecticide’s action on an organism that are responsible for control.
• Insecticide Activity on Target Pest :
– Lethal activity
– Sub-lethal activity
– Repellency
– Anti-feedance and oviposition deterrence
– Curative activity
Lethal activity results in direct mortality of the pest
Adulticides:
Contact w/ adults
Ovicides:
Residue under eggs
Leaf or Fruit
Larvacides:
Residue over eggs (ovi-larvicidal)
Ingestion/contact w/ larva
Spray Deposition
CM Cumulative Life-Stage Activity Bioassays
Life Stage Activity of Insecticides on Codling Moth
% Live Adults
% Egg Hatch
# Larval Entries
100
75
50
Control
Guthion
Calypso
Delegate
Proclaim
Altacor
0
Rimon
25
MSU Trevor Nichols Research Center
Insecticidal Activity on Codling Moth
Compound
Life-stage Activity
Mode of Exposure
Organophosphates
Eggs, Larvae, Adults
Contact / Ingestion
Pyrethroids
Eggs, Larvae, Adults
Contact / Ingestion
Rimon
Eggs
Larvae
Adult
Under / over egg contact
Ingestion
Contact – sublethal effects
Delegate
Eggs, Larvae
Ingestion / egg contact
CM Virus
Larvae
Ingestion
Neonicotinoids
Eggs, Larvae, Adults
Ingestion / contact
Proclaim
Eggs, Larvae
Ingestion / over egg contact
Altacor/Belt
Eggs, Larvae
Ingestion / over egg contact
Optimal Timing for Codling Moth Control
Adults
Larvae
175-200 DD b50
100
C M em ergence
Eggs
Petal Fall
250 DD b50
80 Bio+100 DD Altacor/Belt
Neonics Proclaim
Delegate
60
CM virus
Rimon
Organophosphates
40
20
0
1
2
3
4
5
Time
6
7
8
Sub-lethal activity affects
the subsequent generation of the pest
Reduced fecundity or
Nonviable eggs
Leaf or Fruit
Spray Deposition
Sublethal Activity of Novaluron on Codling Moth
100.00%
90.00%
Egg Hatching Rate(%)
80.00%
70.00%
60.00%
Control
50.00%
Novaluron
40.00%
30.00%
20.00%
10.00%
0.00%
Ingestion
Residual Contact
Treatment Method
Direct Spray
Esteem IGR Reduces Overwintering Survival
in Plum Curculio (Whalon et al.)
Eggs in
Esteem
Treated PC
Fall
Fall Migration?
Migration?
Repellents cause the pest to
actively avoid the treated substrate
Antifeedants and Oviposition Deterrants
reduce the desirability of the crop
as a food source or egg laying host for the pest
No Feeding or Egg Laying
Fruit
Residue Profile on Apple Leaves
10
5
0
-5
-10
Neonicotinoids
Curative activity is lethal action on a pest
post-infestation resulting from the transitory penetration
of the insecticide into plant tissue.
Spray
Fruit
Curative Activity of Insecticides on Plum Curculio Larvae
Untreated Check
A
Intrepid
A
A
Esteem
Rimon
A
Avaunt
A
ABC
Calypso
BCD
Assail
D
Actara
CD
Guthion
0
0.5
1
Mean larvae per fruit
1.5
2
Insecticide Penetration Profiles in Early Season Apples
Curative Activity of Insecticides on Apple Maggot Larvae
Insecticide Penetration Profiles in Apple Subsections
Proportion of active ingredient
100%
90%
5mm+ inside to core
80%
5mm center flesh
70%
60%
2mm outside flesh
50%
Skin
40%
30%
20%
10%
0%
Imidan
Calypso
Actara
Delegate
Chemical Activity Properties
Compound
Mode of Action Mode of
Entry
Insecticidal Activity Speed of
Activity
Organophosphates
Nerve Poison
Contact/Ingest Lethal, Curative
Carbamates
Nerve Poison
Contact/Ingest Lethal
Pyrethroids
Nerve Poison
Contact/Ingest Lethal / Repellent
Fast
Insect Growth
Regulators
Hormonal
Ingestion /
egg contact
Lethal / Sublethal
Slow
Spinosyns
Nerve Poison
Ingestion
Lethal
Fast
Oxadiazines
Nerve Poison
Ingest/contact
Lethal
Slow
Neonicotinoids
Nerve Poison
Contact/Ingest Lethal / Antifeedant
Ovipos deterrence
Curative
Moderate
Diamides
Ryanodine
Receptor
Modulators
Ingestion
Moderate
Lethal
Fast
Moderate
Optimal Timing for Apple Maggot Control
Adults
A M em ergence
Period
80
Delegate
SpinTor
GF-120
Diamides
40
Larvae
Egg Laying
Adult targeted
Cover spray
Imidan
Neonics
100 Preoviposition
60
Eggs
Curative
Sprays
Imidan
Neonics
20
0
1
2
3
4
5
Time
6
7
8
Optimal Timing for Plum Curculio in Stone Fruits
Adult activity
N u m b er of P C
100
Petal Fall Shuck-Off
80
Eggs
Larvae
Curative
Actara
Imidan Actara
Avaunt
60
40
Rimon
Delegate
20
0
1
2
3
4
5
Week
6
7
8
Identifying Modes of Insecticidal Activity
(drawing by Marlene Cameron)
(d)
a)
b)
c)
d)
e)
Oviposition deterence
Antifeedant
Repellency
Curative
Sub-lethal
For many of the RR insecticides “Lethal
and non-lethal modes of insecticidal
activity work in concert to achieve the
overall crop protection seen in the field.”
(Wise and Whalon 2009; Biorational Control of
Arthropod Pests: Application and Resistance
Management. In I. Ishaaya and A. Rami Horowitz (eds.),
Biorational Control of Arthropod Pests: Application and
Resistance Management: Springer Pub. Ltd. )
How Insect Populations Develop Resistance
THREE GENOTYPES
RR
Homozygous
Resistant
RS
Heterozygous
SS
Homozygous
Susceptible
Seasonal Program Under Resistance Management
Apr
Jun
May
Delegate Delegate
Jul
Aug
Altacor Altacor
PF
Bloom
adults
egg
laying
0 100
250
hatch
500
1000
Codling Moth Degree-days (base 50 F° post-biofix)
Seasonal Program Under Resistance Management
Apr
Jun
May
Jul
Voliam flexi Altacor
Aug
Belt
Assail
PF
Bloom
adults
egg
laying
0 100
250
hatch
500
1000
Codling Moth Degree-days (base 50 F° post-biofix)
MSU Resistance Management Incompatibility Chart
Factors that Influence Pesticide Wash-off
(image by Marlene Cameron)
•
•
•
•
Rainfall Characteristics
Penetrative & Translocative Properties of the Compound
Insecticide Inherent Toxicity and Application Rate
Drying time, Persistence, and Additives
Translocation and systemic mobility:
a. Translaminar ‐penetration of a foliar applied pesticide from the adaxial cuticular surface of the leaf, through the epidermis layer and distributing into the mesophyll on the abaxial side. b. Acropetal ‐ horizontal mobility in the plant xylem from central leaf tissue to the marginal ends. c. Basipetal ‐ movement of the insecticide within the phloem from the site of application in the downward direction.
Physical and Chemical Properties
Compound Class
Residual
plant)
(on
Systemic
Characteristics
(foliar)
Systemic
Characteristics
(fruit)
Organophosphates
Long
Surface
Surface
Pyrethroids
Short
Cuticle Penetration
Cuticle Penetration
Medium
Translaminar &
Acropetal
Systemic
IGRs
Medium - Long
Translaminar
Cuticle Penetration
Spinosyns
Short - Medium
Translaminar
Cuticle Penetration
Diamides
Medium - Long
Translaminar
Cuticle Penetration
Neonicotinoids
Imidan
Assail
Fruit Residues
Fruit Residues
0.1
A m o u n t u g /g o f a c e t a m ip r id l
0.75
0.5
0.25
0.075
0.05
0.025
0
0
0 inch rain
1.0 in rain
0 inch rain
2.0 in rain
Leaf Residues
1.0 in rain
2.0 in rain
Leaf Residues
5
A m o u n t u g /g o f a c e t a m ip rid
20
A m o u n t u g /g o f p h o s m e t
A m o u n t u g /g o f p h o s m e t
1
15
10
5
4
3
2
1
0
0
0 inch rain
1 in rain
2 in rain
0 inch rain
1 in rain
2 in rain
Delegate
Altacor
Fruit Residues
Fruit Residues
A m o u n t u g /g o f s p in e t o r a m
0.04
0.03
0.02
0.01
0
0 inch rain
1.0 in rain
2.0 in rain
Leaf Residues
Leaf Residues
A m o u n t u g /g o f s p in e t o r a m
2.5
2
1.5
1
0.5
0
0 inch rain
1 in rain
2 in rain
Rainfastness Rating Chart
General Characteristics for Insecticide Chemical Classes
Rainfastness ≤ 0.5 inch
Rainfastness ≤ 1.0 inch
Rainfastness ≤ 2.0 inch
Fruit
Leaves
Fruit
Leaves
Fruit
Leaves
Organophosphates L
M
L
M
L
L
Pyrethroids
M
M/H
L
M
L
L
Carbamates
M
M
L
M
L
L
IGRs
M
H
Neonicotinoids
M,S
H,S
L,S
L,S
L,S
L,S
Spinosyns
H
H
H
M
M
L
Diamides
H
H
H
M
M
L
Avermectins
M,S
H,S
L,S
M,S
L
L
Insecticide
Class
•H – highly rainfast (≤30% loss), M – moderate (≤50% loss), L – low (≤70% loss), S-systemic residues
•Michigan Fruit Management Guide E154 http://bookstore.msue.msu.edu/
Apple Insecticide Precipitation Wash-off
Re-application Decision Chart:
Expected codling moth control in apples, based on each compound’s inherent toxicity to CM
larvae, maximum residual, and wash-off potential from rainfall.
Insecticides
Rainfall = 0.5 inch
Rainfall = 1.0 inch
Rainfall = 2.0 inches
*1 day
*7 days
Imidan
X
Asana
X
*1 day
*7 days
*1 day
*7 days
X
X
X
X
X
X
X
Calypso
X
X
X
X
Assail
X
X
X
X
X
X
X
X
X
X
Delegate
X
X
Altacor
X
X
Belt
X
X
Proclaim
Rimon
X
X
* Number of days after insecticide application that the precipitation event occurred.
X – Insufficient insecticide residue remains, thus re-application is recommended.
20th
Century IPM
Industrial Age
“Time for another poison”
21st Century IPM
Information Age
“What optimal selection of IPM
tools will best exploit the pest’s
weaknesses, reduce total inputs,
minimize impacts on beneficials,
while protecting human and
environmental resources?”