Pesticide breakdown Some pesticides break down very quickly in a matter of days or even hours. Others may remain in the environment for a year or more. Adsorption is the physical attachment of pesticide molecules to soil particles. The strength of the bonds depends on the interaction of the chemical properties of the pesticide, its concentration in soil water, the pH of the soil and the composition of the soil (percentage of sand, silt, loam, clay and organic matter).
If it adheres to soil, the pesticide is unlikely to leach or leak out. Some highly soluble pesticides adhere strongly to soil. The more clay particles and organic matter in the soil, the more pesticide will be retained in the soil and will remain immobile. Strongly adsorbed pesticide molecules do not leach or move unless the soil particles on which they are adsorbed move (erosion) with water.
The longer the molecules of a pesticide remain, the more likely it is that microbiological degradation will occur, reducing the risk of leaching and runoff. Photodegradation Photodegradation is the breakdown of pesticides by light, particularly sunlight. Photodegradation can destroy pesticides in foliage, soil surface, and even in the air. In conversations about pesticides, certified organic agriculture, conventional production and backyard gardening, questions are often raised about what pesticides can be used, where pesticides come from, and the associated risks to people, pollinators and the environment.
Terms such as “synthetic”, “toxicity”, “natural”, “organic” and “chemicals” are sometimes used in a confusing way. The purpose of this fact sheet is to provide a summary for understanding these and other terms related to pesticides in organic and conventional crop production. As the population of these organisms increases, degradation accelerates and the amount of pesticide available to control the pest decreases. However, at all levels, regulators are working together to achieve the common goal of helping to protect Canadians from any risks posed by pesticides and to ensure that pest control products comply with what is stated on the label.
However, degradation is harmful when a pesticide is destroyed before the target pest is controlled. Factors that influence the photodegradation of pesticides include the intensity of sunlight, the properties of the site of application, the method of application and the properties of the pesticide. Biochemical pesticides control pests through non-toxic mechanisms, such as pheromones, that interfere with insect mating. Pests must be accurately identified and pesticide applications should be made only when necessary, using the least amount needed for proper pest control.
Volatilization can reduce control of the target pest because there is less pesticide left at the target site.