Certified Crop Advisor Practice Exam

Which insecticides are most persistent in the soil?

1. Neonicotinoids

2. Organophosphates

3. Pyrethroids

4. Carbamates

The correct answer is: Pyrethroids

The most persistent insecticides in the soil are indeed neonicotinoids. These products have a strong affinity for soil particles, which leads to a longer half-life and prolonged activity within the substrate. This persistence is largely because neonicotinoids are designed to have systemic properties, permeating plant tissues and affecting insect pests over time. Their chemical structure allows them to bind tightly to the soil, resisting degradation from environmental factors. In comparison, organophosphates, pyrethroids, and carbamates typically degrade more rapidly due to their chemical properties and higher susceptibility to microbial degradation and photodecomposition. This means that while they may be effective insecticides, they do not maintain their residual action in the soil as long as neonicotinoids do. Understanding the persistence of these insecticides is crucial for effective pest management and environmental safety considerations in agricultural practices.