How does dichlorvos affect ticks? - briefly
Dichlorvos inhibits acetylcholinesterase in tick nervous systems, causing uncontrolled nerve firing, paralysis, and rapid death. Effective concentrations are low, making it a potent acaricidal agent.
How does dichlorvos affect ticks? - in detail
Dichlorvos, an organophosphate insecticide, interferes with the nervous system of ticks by inhibiting acetylcholinesterase, leading to accumulation of acetylcholine at synaptic junctions. This disruption causes uncontrolled muscular activity, paralysis, and rapid death.
Acute toxicity:
- Mortality rates exceed 90 % within 24 hours at concentrations of 0.5 mg L⁻¹.
- Lethal dose (LD₅₀) for adult Ixodes ricinus ranges from 0.2 to 0.4 µg per tick, depending on species and developmental stage.
Sublethal effects:
- Reduced attachment efficiency to hosts.
- Impaired blood‑feeding behavior, decreasing engorgement weight by up to 35 %.
- Delayed molting in larvae and nymphs, extending development time by several days.
- Altered locomotion patterns, increasing susceptibility to environmental stressors.
Resistance considerations:
- Repeated exposure selects for acetylcholinesterase variants with reduced binding affinity.
- Field populations with documented resistance exhibit LD₅₀ values up to threefold higher than susceptible strains.
Application methods:
- Spray formulations applied to vegetation achieve contact exposure for questing ticks.
- Pour‑on treatments on livestock provide systemic protection, though absorption rates vary with skin thickness.
- Bait stations targeting host animals can deliver indirect exposure through blood meals.
Environmental impact:
- Rapid degradation in soil and water (half‑life ≈ 2 days) limits persistence.
- Non‑target arthropods experience acute toxicity; mitigation includes timing applications to avoid peak pollinator activity.
- Residue levels in milk and meat remain below regulatory limits when used according to label instructions.
Overall, dichlorvos exerts potent neurotoxic action on ticks, delivering high mortality and disrupting key life‑cycle processes. Effective control requires adherence to dosage guidelines, rotation with alternative acaricides to curb resistance, and consideration of ecological side effects.