BI207-- chemical control limitations

chemical insecticides

• most widely used method of pest control

• mode of action: most chemicals act on the insect nervous system and cause rapid death

• types:

  • botanicals

  • synthetic insecticides

  • insect growth regulators

limitattions to use of pesticides

1. environmental contanimation

2. effects on non target organisms

3. chronic occupational exposure

4. human health

5. residues (in food crops)

6. pest resistance (in insects)

7. pest resurgence (pest returning after beneficial natural enemies killed)

8. induction of secondary pest problems (former non pest species that were controlled by natural enemies)

entry routes for insecticides in water (image)

• high levels of contanimation found in water sources, higher than legal limit

environmental contanimation— water

• pesticide removal during wastewater treatment often poor

• sometimes resulted in concentrations in effluent higher than influent

environmental contamination— soils

• seeds coated with pesticides to prevent being eaten— leeches into soil

• found mixtures of pesticides within soils that were sampled

• some havent been used in years yet still persist in soil

• impacts soil biodiversity and health

environmental contamiantion— nectar and pollen

• pesticide residues found in flowers that are toxic to bees

• exposed to mixture of compunds

• only 1 honeybee species— total 98 species of wild bees

• originally pesticides only tested their effects on worker honeybees— didnt test effect of repeat exposure or potential risk to larvae

non target organisms

• terrestrial above ground

• terrestrial below ground

• aquatic— freshwater [marine]

• invertebrates— insects

non target organisms— how are organisms exposed

• acute vs chronic exposure

• secondary exposure

• indirect effects on food source or habitat

• e.g. dung beetles affected by pesticides, resulting in more parasites found due to less dung beetles breaking it down

• antiworming drugs found in feaces of cows and sheeps— prevents effective decomposing, reduces soil fertility, kills insects trying to decompose it

insecticide and pollination

effects

• learning and memory

• foraging and homing ability

• flower visitation

• pollination

below ground invertebrates

• earthworms, acari and nematodes heavily affected

exposure routes

who

• sprayers, farm workers, manufacturers, transporters, soldiers, public, scientists

why

• direct contact, aerial drift, water, food chain, bad practice

how

• skin, eyes, ingestion, respiration

DDT and malaria

before DDT: contro lfocused on mosquito larvae and disease itself

• anti malarial drugs e.g. quinine

• larvae targeted by draining/ filling in habitats or treating with oils and copper acetoarsenite every two weeks

1955: WHO delcares that global eradication possible— adults taregted, housed sprayed, effective for 6 months, in india cases dropped from 47 million (1947) to 0.1 million (1965), but back to 7-10 million in 1977

• killed birds

• residue found in fruit and produce

• growing rates if cancer found in people

DDT and human health

• extremely presistent in environment and human body

• bioaccumulates

• still used for control of disease vectors (e.g. mosquitoes)

linked to range of conditions

• diabetes

• endocrine disruption

• reproductive phsyiology (reduced sperm count)

• miscarrage

• cognitive development of infants

• carcinogenicity (liver, pancreas)

persistence

• some pesticides are persistant pollutants, they do not degrade in soil or when exposed to UV radiation

• bioaccumulation: toxins build up in an individual organism over time

• bio magnification: toxins build up as they pass from organism to organism through food chain

sheep dip

• uk 19080s/90s organophosphates used as sheep dip

• sheep scab was a notifiable disease and dipping was compulsory

• farmers satrted suffering from multiple health issues

• headaches, giddiness, blurred vision— had to be investigated

food residues

many foods found with pesticides

one neonicotinoid: >90% fruit and veg, 90% of honey samples

two neonicotinoids: 72% fruits, 45% of veg, 50% of honey

but all below max residues

more research into human health effects needs to be done

ireland — Pesticide Control Labratory (PCL) monitors

• pesticide residues in food

• pesticide residues in animal feed

• analysis of formulated products

why move towards less insecticide use?

• problems with insectide resistance

• cost of insecticide

• consumer backlash against environemntal and human health concerns— non target organisms

• development of alternative controls