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ASP 2 > Pesticides > Flashcards

Pesticides Flashcards

1
Q

What is a pesticide?

A

Any substance or mixture intended to prevent, destroy, repel, and mitigate any pest and intended for use as a plant regulator, defoliant or desiccant

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2
Q

How can pesticides be categorized?

A

based on intended purpose
based on application
based on relation to target pest (mode of action)
based on chemistry

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3
Q

What are pesticide categories based on intended purpose?

A

insecticides (can be for a specific species or point in lifecycle)
herbicides (most widely used)
fungicides
rodenticides (mostly for food storage)

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4
Q

What are pesticide categories based on application?

A 
How?
air application - plane, tractor, human
plastic covered
broadcast vs. targeted
When?
same time as planting (treated seed or next to seed)
specific stages of growth
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5
Q

What are pesticide categories based on mode of action?

A

contact - must contact pest, some more stable than others that require re-application, can remain on plant until insect lands (lots of fungicides and insecticides)
systemic - translocated with plant tissue, relies on persistence, pest ingests tissue and (active) pesticide

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6
Q

What makes a product a pesticide?

A

intent, claims, composition, knowledge that it will be used as a pesticide

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7
Q

What are the benefits of pesticide use?

A

higher yields
improved quality
reduced labor, machinery, fuel

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8
Q

How has pesticide use changed over time?

A

boom of use started in 1960s - 1980s - increased planted acres + increased treated acres
downward trend since 1980 - improved application methods and better ingredients - need less
*many old pesticides still used
*USDA no longer tracks pesticide/fertilizer use

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9
Q

What are the drivers of changes in pesticide use?

A

changes in pest pressures
environmental and weather conditions
crop acreages have changed
ag practices
cost-effectiveness (value of damage reductions vs. control costs)
regulations
access to experts
tech innovations
new products that decrease per acre application rate
adoption of GE crops
price of crops, pesticides, other practices
IPM
farm and energy policy
risk and uncertainty (responsive vs. preventative - monitoring costs)

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10
Q

What are different classes of pesticides based on chemistry?

A 
chlorinated hydrocarbons
organophosphates
carbamates
triazine herbicides
phenoxy herbicides
botanicals - pyrethroids,
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11
Q

What are chlorinated hydrocarbons (organochlorines)?

A

insecticides - mostly off the market now
act as nerve agents
widely used in 1940s-1960s

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12
Q

What are examples of chlorinated hydrocarbons?

A

DDT, aldrin, dieldrin, heptachlor, lindane

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13
Q

How do chlorinated hydrocarbons work?

A

concentrate in the fatty tissue and bioaccumulate
act as nerve agents
disrupt calcium mobilization

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14
Q

What are concerns with chlorinated hydrocarbons?

A

very persistent in the environment
toxic to non-target organisms - fish especially (lindane)
bioaccumulation - concentration in food chain, harm predatory birds

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15
Q

What are organophosphates?

A

insecticides - most commonly used
replaced many organochlorines in the 1970s
many are restricted use

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16
Q

What are examples of organophosphates?

A

diazinon, malathion, methyl parathion, terbufos

17
Q

What are concerns with organophosphates?

A

can be extremely toxic to fish and birds
generally higher mammalian toxicity

better - less persistent in environment, don’t bioaccumulate

18
Q

How do organophosphates work?

A

cholinesterase inhibitors

increase toxicity by all routes of exposure

19
Q

What are carbamates?

A

insecticides - many are systemic, some regulators of plant growth
subclass - thio- and dithiocarbamates - many common herbicides
act as acetylcholinesterase inhibitors

20
Q

What are subclasses of carbamates?

A

aldicarb - one of most toxic ever approved
carbaryl - one of most widely used (residential)
carbofuran - banned in granular form
thio and dithiocarbamates - include a sulfur molecule, includes butylate, EPTC

21
Q

What are concerns of carbamates?

A

mobile in soil and groundwater (aldicarb)
extreme acute toxicity in mammals (aldicarb)
toxic to birds

better - low-moderate environmental persistence; thio and dithios have lower toxicity

22
Q

What are triazine herbicides?

A

photosynthetic inhibitors
among most widely used

subject to special review - stability in water

23
Q

What are examples of triazine herbicides?

A

atrazine, cyanazine, metribuzin

24
Q

What are phenoxy herbicides?

A

very widely used (farm and home)

act as synthetic plant hormones (auxin-like)

25
Q

What are examples of phenoxy herbicides?

A

2,4-D and 2,4,5-T

26
Q

What are botanical pesticides?

A

come from other plants or synthetics
ex) pyrethroids, rotenone (from bean), strychnine (poison), nicotinoids (from tobacco) - neonicotinoids, imidicloprid, synthetics

27
Q

What are pyrethroids

A 
come from chrysanthemum or synthetic (lots)
insecticides
ex) Ambush
have higher insect:mammal selectivity
shorter persistence
28
Q

What factors effect pesticide toxicity or negative impacts?

A

have a potential effect on other organisms (beyond toxicity)

also depends on: stability or persistence, form, solubility and transport potential, breakdown products

29
Q

How do pesticides move?

A

laterally - with runoff or sediment
drift from spray
leach into saturated zones
by wind or rain (into non-ag areas)

30
Q

What is selectivity?

A

the differential sensitivity of the organism to the pesticide
ex) kills only certain type of plant or certain stage of life

31
Q

What is resistance?

A

“inherited ability of the plant to survive and reproduce following exposure to a herbicide dose normally lethal to the wild type”

32
Q

How many plants/insects have developed resistance so far?

A

500+ insects
100 dicots
70 monocots

33
Q

What are major issues with pesticides?

A

resistance - norm not the exception
non-target organism impacts - kill beneficial insects
on-site this can cause outbreak of secondary pest
off-site impacts birds, bees, fish, humans
survival and reproduction in face of resistance

34
Q

How does survival and reproduction happen?

A

self-pollinating weed that survives yields viable seeds with a heritable resistance - often single site mutation
insect that survives needs to find a resistant mate to reproduce successfully

35
Q

What is refugia?

A

maintaining a susceptible population as part of management

36
Q

How does resistance develop?

A

repeated production of single or few crops
repeated application of same or similar chemicals
both of these are common characteristics of production system currently
eventually, continued application favors resistant members

37
Q

What is selection intensity?

A

a function of effectiveness, frequency, duration

38
Q

What are types of resistance?

A

metabolic - detox the pesticide
target site - alteration to binding site
delayed penetration (no longer active) - insect or plant
behavioral - avoidance for example

39
Q

What is dose response?

A

survival percentage to the application rate, 100% isn’t the norm

ASP 2 (9 decks)

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