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SC1 305 PESTICIDES

Pesticides
• Pesticides are chemicals that kill pests, and are
categorized by the types of pests they kill
...


Pesticides used in the past

• The types of substances people have used as pesticides have
changed over time
...

• Some of these inorganic pesticides are still used today e
...

–
–
–
–

sulfur is still used as a fungicide
copper is used as an algicide
lead and arsenic were used as insecticides until World War II
chromium, copper, and arsenic have been used as wood preservatives
to prevent microorganisms from causing wood decay
...

– Lead and arsenic are no longer used as insecticides
– the use of mercury as a fungicide has been restricted
– use of arsenic as a wood preservative is being phased out by
environmental agencies

Synthetic pesticides
• Around World War II, synthetic organic chemical industry began to
develop
...

• Commercial production of DDT began in 1943
...

• Today most of the organochlorine pesticides have been banned in
many countries because of the tendency of these compounds to
persist in the environment and bioaccumulate in animals
...

• The organophosphate and carbamate pesticides
affect the nervous system
• As a group, the organophosphate and
carbamate pesticides are probably the most
widely used insecticides, although many are
being restricted because of their toxicity
...

• Safer than the organochlorines,
organophosphates, and carbamates, although
some synthetic pyrethroids are toxic to the
nervous system
...


Biopesticides
• Biopesticides derived from natural
materials
• They fall into three major classes:
– microbial pesticides contain
microorganisms as active ingredient
– plant-incorporated protectants
produced by plants from incorporated
genetic materials
– biochemical pesticides excreted by
animals or extracted from plants

Pesticide residues
• Pesticide residues are the materials that
remain on plants and food when a crop is
treated with a pesticide
...


• Controlled by Government agencies
• Scientists will continue to develop newer
approaches to insect pest management that
are considered to be safer than the use of
broad-spectrum pesticides
...


Formulations
• Classified as liquids or solids on the basis of
their physical state in the container at the
time of purchase
...
g
...


Important Definitions
• Active Ingredient (Ai) - the actual chemical in
the product mixture that controls the pest
• Inert Ingredient - other materials added with
the AI when the product is formulated
• Phytotoxicity - plant damage
• Adjuvant - product added to spray tank to
assist pesticide in its application

Pesticide Formulation
active ingredient (Ai)
each Ai will be listed

+

inert ingredients
water, emulsifiers
solvents, dry carrier material
stabilizers, dye
surfactants: spreaders, stickers
wetting agents

Product Formulations
• Active and Inert Ingredients composition
declaration

Lexone DF
• Active Ingredient
•

Metribuzin (4-amino-6-1-1 dimethlyethly3-methythio 1,2,4,triazine 5 4H-one)

• Inert Ingredients
•

TOTAL

•

EPA Reg
...
12333-344

25%

75%
100%

Pesticide suffixes

Brand Name Abbreviations
• Often brand names include abbreviations that
describe something about the formulation
D
G
SP
S
WP
EC
DF
WDG

–

–
–
–
–
–
–
–

WSP
dust
ULV
granular
RTU
soluble powder
GL
solution
LO
wettable powder
emulsifiable concentrate
dry flowable
water dispersible granule

–
–
–
–
–

water soluble packet
ultra low volume
ready to use
gel
low odor

Why Add Inert Ingredients?
1
...
Inerts make measuring and mixing pesticides
easier
3
...
Makes the Ai work better

• Better penetration
• More selectivity
Univ
...


Deciphering the Ai Code in Product
Names
80SP
80% active ingredient
by weight
Soluble Powder
1EC
1 lb Ai/gallon
emulsifiable concentrate

40DF
40 % active ingred
...


• Ready –to-use:
– Dusts (D)
– Granules (G)
– Pellets (P)

• Concentrates intended to be mixed with water:
– wettable powders (WP)
– dry flowables (DF)
– soluble powders (SP)

Dusts

• Dusts are manufactured by the sorption of an active
ingredient onto a finely-ground, solid inert such as talc,
clay, or chalk
...

• Dusts can provide excellent coverage
• Dusts are generally applied as spot treatments for insect
and disease
• Formulation permits the delivery of an insecticide into
cracks and crevices, behind baseboards and cabinets, etc
...


• Commercial pest control operators use dusts effectively in
residential and institutional settings
• Fine particle size that creates an inhalation and drift hazard
...

• Applied dry and usually are intended for soil applications
where they have the advantage of weight to carry them
through foliage to the ground below
• The larger particle size of granules, relative to dusts,
minimizes the potential for drift
...

• Low dermal hazard
...

Sometimes attractive to nontarget organisms such as birds
...

• The active ingredient is combined with inert materials to
form a slurry (a thick liquid mixture)
...

• Pellets are typically used in spot applications
...

• Drawback
– potential to roll on steep slopes and thereby harm nontarget
vegetation or contaminate surface water

Dry Formulations
Baits (B)
Include granules and pellets
A bait is an example of a dry product that is
applied without mixing

Wettable powders
• Very common formulation
• Wettable powders are finely divided
insoluble solids, typically mineral clays, to
which an active ingredient is sorbed
...

• Diluted with water and applied as a liquid
spray to forms a suspension in spray tank
...

• Provide an ideal way to apply (in spray form)
an active ingredient that is not readily
soluble in water
...


Water dispersible Granules (Dry flowables)
• Water dispersible granules (WDG) are also known
as Dry flowables (DF)
• The dry powder is aggregated into granular
particles with inert fillers such as clay
...


(WDG) Dry Flowables (DF)
• They require moderate
agitation to keep them
in suspension and leave
visible residues, similar
to those of wettable
powders
...

• The amount of active ingredient in
soluble powders ranges from 15 to 95
percent by weight; usually >50
percent
• Soluble powders have all the
advantages of wettable powders and
none of the disadvantages except the
inhalation hazard during mixing
...


Microencapsulated materials (M or
ME)
• Microencapsulates consist of a solid
or liquid inert (containing an active
ingredient) surrounded by a plastic or
starch coating
...

• Liquid forms of microencapsulates are
further diluted with water and applied
as sprays
...


Adjuvants
• An adjuvant is any material that when added
to a spray solution enhances or modifies the
action of a pesticide
...

• But farmers prefer those adjuvants that can be
added to the spray solution on-farm to help
get the most out of their money spent on
spraying programs
...
Modifying how chemical components or
products interact in the spray tank
• The two most common at this level are
compatibility agents and drift retardants
...

• These products are normally factory fitted into
the formulation
...

• Many spray adjuvants can be added to a tank mix to increase its
viscosity
...

• This results in an upward shift of the droplet spectrum to reduce
driftable ‘fines’
...


2
...


• Surfactants are used to lower the surface tension
• Caution: to much s
...
reduction can negatively
affect:
– Retention time of surface
– High rate of evaporation

3
...

• Enhanced by some surfactants which reduce dynamic
surface tension to a sufficiently low level
...

• This cuticle-disrupting property of some adjuvants
may cause injury to the target
• Drawback: Certain crop oils, when exposed to heat or
UV on leaf surfaces, cause disruption to cell
membranes resulting in phytotoxicity to crop plants

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