Neonicotinoid Residues on Filter Paper Lack Insecticidal Activity.

Area of Science:

• Agricultural Science
• Environmental Toxicology
• Entomology

Background:

• Neonicotinoid insecticides are widely used for pest control in agriculture, forestry, and urban environments.
• Assessing insecticide toxicity often involves evaluating dry residues on treated surfaces like filter paper.
• Standardized testing methods are crucial for accurate risk assessment of pesticides.

Purpose of the Study:

• To investigate the reliability of filter paper as a substrate for evaluating the toxicity of neonicotinoid insecticides.
• To compare the efficacy of neonicotinoids against common insect pests on different surfaces.
• To determine if neonicotinoid adsorption to filter paper affects toxicity assessments.

Main Methods:

• Bioassays were conducted using four neonicotinoids (acetamiprid, dinotefuran, imidacloprid, thiamethoxam) and bifenthrin (pyrethroid).
• Toxicity was evaluated on filter paper, leaf discs, and glass plates using insect species Hippodamia convergens and Nezara viridula.
• Additional tests explored neonicotinoid adsorption and bioavailability on filter paper under various conditions.

Main Results:

• Neonicotinoids on filter paper showed minimal insect mortality compared to untreated controls.
• Nearly 100% mortality was observed when insects were exposed to neonicotinoids on leaf discs and glass plates.
• Bifenthrin residues on filter paper, leaf discs, and glass plates were significantly toxic.
• Neonicotinoids were adsorbed by filter paper, rendering surface residues non-toxic, but remained active when eluted.

Conclusions:

• Filter paper is an unreliable substrate for evaluating neonicotinoid toxicity due to insecticide adsorption.
• Neonicotinoid toxicity is significantly underestimated when assessed using dry residues on filter paper.
• Alternative substrates like leaf discs or glass plates are recommended for accurate neonicotinoid toxicity testing.