Imidacloprid (also known as imidacloprid) is a highly effective, broad-spectrum neonicotinoid insecticide widely used in agriculture to control piercing-sucking pests such as aphids, whiteflies, and leafhoppers. It has systemic, contact, and stomach poison effects, paralyzing and killing pests by disrupting their nervous system. It is popular with farmers due to its low toxicity, rapid action (effective within one day), and long residual period (approximately 25 days).
The following are detailed characteristics and applications of imidacloprid:
1. Mechanism of Action and Characteristics: It has systemic action (absorbed from roots or leaves and translocated throughout the plant), contact action, and stomach poison action. Characteristics: Highly effective, low toxicity; efficacy is positively correlated with temperature (higher temperatures result in better efficacy). Target Pests: Primarily used to control piercing-sucking pests such as aphids, planthoppers, leafhoppers, thrips, whiteflies, and flea beetles. Applicable Crops: Widely used in various crops including rice, wheat, corn, cotton, potatoes, fruit trees, and vegetables.
2. Usage and Application Scenarios: Agricultural Spraying: Routine control of aphids, whiteflies, etc. Seed Treatment: Used for seed coating to control underground pests and aphids during the seedling stage. Household Hygiene: Commonly used as an ingredient in cockroach baits; the gel-like design allows for controlled dosage control, effectively controlling cockroaches and ants.
3. Precautions and Safety: Environmental Impact: Highly toxic to pollinating insects such as bees, severely affecting crop pollination; avoid application during flowering periods. Pesticide Residue: Although low in toxicity to humans and animals, strict adherence to application intervals is necessary, especially on crops such as bananas, where there have been records of imidacloprid residue exceeding the standard (GB 2763—2021).
First Aid for Poisoning: In case of accidental ingestion, seek immediate medical attention for symptomatic treatment; there is no specific antidote.
Toxicity of Insecticides to Bees and Colony Collapse
Imidacloprid is acutely toxic to bees: its LD50 ranges from 5 to 70 nanograms per bee. [34] The ability of bee colonies to metabolize toxins varies, which explains the wide range of LD50s. Imidacloprid is more toxic to bees than the organophosphate insecticide dimethoate (oral LD50 of 152 nanograms per bee) or the pyrethroid insecticide cypermethrin (oral LD50 of 160 nanograms per bee). Unlike most other insecticides, the oral toxicity of imidacloprid to bees is higher than its contact toxicity. The acute contact LD50 is 0.024 micrograms of active ingredient per bee.
Laboratory studies have shown that sublethal doses of imidacloprid impair navigation, foraging behavior, feeding behavior, and olfactory learning in bees (Apis mellifera). However, despite numerous laboratory studies demonstrating the potential toxicity of neonicotinoid insecticides, most field studies have found limited or no impact on bees.
In bumblebees, exposure to 10 ppb of imidacloprid reduced their natural foraging behavior, increased worker mortality, and led to reduced larval development. A possible mechanism is that long-term exposure to imidacloprid significantly downregulates the mevalonate pathway, which helps explain the cognitive impairment caused by imidacloprid.
