Lecture 3 Flashcards
Chemical pesticides
Control pests: insects, weeds, plant disease
Decrease spread of insect borne disease
Increase yields in crops
Classified by target species:
Insecticides: control insects
Herbicides: weed control
Fungicides: control fungal growth
pesticides used in Mid-1800s to pre-WWI
- “natural pesticides”
-Highly toxic metals (arsenic/lead), nicotine
DDT was discovered (1939)
-Used for insect control
-was cheap and easily made
-people weren’t dying right away when used (less poisonous)
-WWII used to kill bedbugs and other insects on contact
-Kill mosquitos to decrease spread of malaria
DDT and the start of environmentalism in the 20th century
-Sprayed everywhere
Noticed bird deaths after town sprayed by air
Also decline in bald eagle, pelican, and peregrine falcon populations
DDT accumulating in bird tissue: Inhibited calcium metabolism, Resulted in very thin egg shells that broke when parent birds sat on them
DDT and biomagnification
-Concentration of DDT increases as it moves up in the food chain
-Banned in the US but still used in many developing countries to combat mosquitos and malaria
Human health effects of DDT
-Acute: nervous system excitation and liver damage
-Lower doses disrupt endocrine and immune systems and is a potential carcinogen
-Insecticides in general are endocrine disrupting chemicals
Impact of DDT:
-Fueled environmental movement along with other chemical pollutants
-Silent Spring was written by Rachel Carson in 1962 (lead to widespread concern about DDT)
organic vs synthetic pesticides
Organic: not man-made (botanicals, microbials)
Synthetic: man-made
Organophosphates
-Carbon-Based Pesticide
- A by-product of nerve gas and chemical warfare research WWII in Germany
-Diazion, Malathion, Orthene
- Synaptic or Nerve poison
Carbamates
-Neurotoxic
Chloronicotinyls
-Synthetic version of nicotine that disrupts the nervous system
-A little goes a long way
Insecticide modes of action:
1) Nerve poisons
2) Muscle poisons (paralysis)
3) Physical toxicants (oils used against aquatic pests to prevent respiration)
4) Repellants (Deet)
Deet
-A repellant effective against mosquitoes, biting flies, fleas, ticks
-The most effective and best studied insect repellent currently on
the market (considered safe)
-But toxic reactions can happen if product is misused
Herbicides
-Weed control due to weeds outcompeting crops for sunlight, water, nutrients.
-Timing of herbicide application depends on the crops emergence from the soil
-Generally less toxicity concern due to mode of
action targeting plant-specific mechanisms
Herbicide that is an Amino Acid Synthesis Inhibitor:
Glyphosate
-Roundup Ready products
-Blocks critical respiration enzyme pathways
Herbicide that is a Cell Membrane Disruptor
-Paraquat
-Activated by sunlight and causes disintegration of cell membranes and chloroplasts
-Herbicide injuries can occur within an hour or two on bright sunny days
Herbicide that is a Plant Growth Regulator
- 2,4-D
-Uptake is mostly through leaves
-Interferes with biological activities and protein synthesis in the plant
Pesticide poisoning
-Early Symptoms: headache, nausea, dizziness, sweatiness,
and increase in salivation, tearing, and respiratory
secretions
-Progressive Symptoms: muscle twitching, weakness,
tremor, incoordination, vomiting, abdominal cramps, and diarrhrea
intentional vs non-intentional poisonings
Delaware Family Poisoned in 2015
-Poisoned while on vacation in Virgin Islands
-Terminix international branch manager knowingly used banned pesticides containing methyl bromide at several locations
-Sprayed the condo beneath the unit rented by the Esmond Family and they became ill 2 days after and were rushed to hospital (inhaled toxins)
-Months later, father and sons were still in serious condition and suffered neurological damage
-Terminix fined $9.2 million and family was paid about $87 million
-Terminix manager 12 months in prison
Pesticides have the potential to…
- Have the potential to move after they are applied
-soil, reach ground water, spread through rainfall
How do herbicides get into waterways and risk
exposure of general population?
1) Runoff from field into
surface waters (may be drinking water sources)
2) Leach through soil into
groundwater
3) Tiles (underneath crop fields
to prevent standing
water on fields, drain into surface waters)
Rotenone
-Organic pesticide derived from botanicals
-very toxic to fish and insects
-linked to increased risk of Parkinson’s disease in humans
-being phased out
Sustainable agriculture
-Decreased to no impact on environment and no adverse impacts to human health
-movement towards this
