Physical and chemical control agent thresholds for action on storage insects

Abstract: Many factors are involved in the successful application of a control measure, whether using a chemical pesticide or whether altering the physical environment by manipulation of temperature humidity or oxygen level. Setting the dosage for a contact insecticide, fumigant or low oxygen level needs to take into account firstly the period of time insects will be exposed while factors such as temperature and humidity are also of critical importance. For any treatment to work at a particular temperature, an adequate presence of the control agent needs to be achieved and maintained where the target pest species are actually living. A spectrum of concentration threshold levels for full efficacy exists among individuals of each species and stage, some responding much earlier than others as concentrations are lowered. Threshold temperature spectra for the upper and lower limits of survival also exist, in close relationship with humidity, again individuals differing in their response.Besides having some knowledge of the thresholds for survival, pest control operators also need to consider temperature thresholds for mobility and flight. Even light levels can have high importance. These aspects and their interrelations are discussed.