DS - Insecticides III Flashcards
How are insect populations monitored to determine if they are above or below the Economic Injury Level (EIL)? (3)
Control Action Threshold (CAT)
- Must be implemented BEFORE the population density of the EIL is met
- Based on strong ecological understanding of target organism
- “Biological control” slower
What is the impact of highly lipophilic insecticides in food chains? (2)
- Accumulate in lipid tissues of higher trophic groups, including humans.
- Resistance to biodegradation (e.g., DDT has a half-life of 3-10 years in soil).
How has the use of DDT affected food webs? (3)
- Used to treat Dutch Elm disease
- DDT concentration in worms living in the soil beneath treated trees was 120 ppb
- Robins that fed on these worms showed 342 ppm of DDT in their brain tissue, leading to death.
How do modern biodegradable pesticides like Diazinon and Parathion compare to older pesticides like DDT in terms of accumulation? (2)
- Modern biodegradable pesticides accumulate less in the environment.
- Older, persistent pesticides like DDT tend to bioaccumulate more significantly in the food chain.
What were the consequences of DDT usage on bird populations? (3)
- Decline in bird populations due to organochlorines like DDT and dieldrin.
- Eggshell thinning, leading to increased egg breakage during incubation.
- Interference with calcium transport in birds’ shell glands. (weaker shells)
What is the significance of neonicotinoids? (3)
- Bird populations decline by 3.5% annually in areas with high neonicotinoid concentrations.
- Loss of pollinators threatens global food supply (70% of crops depend on pollination).
- Neonicotinoids are systemic and accumulate in plant tissues and pollen.
How do flowers attract and direct pollinators? (3)
- Flowers use a complex set of visual cues to help pollinators locate and identify food resources.
- They direct pollinators towards the plant’s anthers and stigma for effective pollination.
- Flowers also provide olfactory cues, allowing pollinators to identify and discriminate between different flowers.
What are the key components of olfactory conditioning in honeybees? (3)
Conditioned Stimulus (CS):
- Odour - The specific scent that triggers the response.
Unconditioned Stimulus (US):
- Reward - Typically a food reward that naturally elicits a response.
Conditioned Response (CR):
- Proboscis Extension Reflex (PER) - The learned response where the proboscis extends in anticipation of receiving the reward after detecting the conditioned stimulus (odour).
How do neonicotinoids affect honeybee memory and learning? (3)
- Inhibit ability to form and recall associations between floral scents and rewards.
- They also prevent bees being able to recall a learned association between nectar reward and floral scent
- Imidacloprid impairs both short- and long-term memory recall.
Where do neonicotinoids target the honeybee brain? (3)
Mushroom Bodies:
- Role: Learning and memory.
- Effect: Impairs formation and recall of floral scent-reward associations.
Kenyon Cells:
- Role: Process sensory information and memory.
- Effect: Disruption affects foraging cognition.
Antennal Lobes:
- Role: Olfactory processing.
- Effect: Hinders detection and response to floral scents.
What is the mechanism by which neonicotinoids affect honeybee behavior? (3)
- Mimics acetylcholine, overstimulating nicotinic acetylcholine receptors (nAChRs).
- Causes neurotoxicity, disrupting learning, memory, and decision-making.
- Synergistic effects with organophosphates enhance membrane depolarization.
Effects of Clothianidin on Honeybee Kenyon Cells (2)
- Membrane Excitability: Changes in responsiveness of Kenyon cells.
- Action Potential Firing: Altered firing patterns due to pesticide exposure.
Effects of Coumaphos on Honeybee Kenyon Cells (3)
- Membrane Excitability: Transient increase followed by decreased responsiveness.
- Depolarization: Slower onset compared to clothianidin.
- Action Potential Firing: Cessation of action potentials due to voltage-gated Ca²⁺ and Ca²⁺-activated K⁺ current inhibition
What are the synergistic effects of neonicotinoids and organophosphates on honeybee Kenyon cells? (2)
- Combined influence enhances membrane depolarization effects in Kenyon cells.
- Tonic depolarization reduces Kenyon cell responsiveness to acetylcholine (ACh).
How does Clothianidin impact honeybee immune function? (2)
- Weakens immune response, leading to increased proliferation of the Varroa parasite.
Higher prevalence of Deformed Wing Virus in bees exposed to Clothianidin
