Many instances of medically important insects developing resistance to insecticides have been documented around the world. Therefore, insecticide control programs should consider the possibility of insect resistance. The following factors impact the development of resistance.
- Characteristics of past insecticide control programs.
- Frequency of insecticide application. More applications per insect pest generation will increase the selection pressure and development of resistance.
- Percentage of insect population treated. Treating a high percentage of the insect population will result in fewer susceptible individuals. The presence of fewer susceptible individuals will cause the resistant individuals to dominate the population more quickly.
- Types of insecticides. A more persistent insecticide produces a greater selection pressure. Consider the potential for the development of cross-resistance between previously used insecticides and those that have not yet been used.
- Insect pest's binomics. The greater any of these are then the possibility of resistance development increases.
- Generations per year.
- Number of offspring.
- Number of life stages exposed to insecticide.
- Proportion of the population exposed.
- Percentage of the insects' life that they are exposed to insecticide.
- Agricultural insecticides. Many insect field populations are exposed directly to agricultural insecticide sprays and indirectly to runoff. For example, riceland mosquitoes are exposed directly because they inhabit agricultural areas. In another example, body lice have developed resistance to malathion, simply because agricultural workers were contaminated with malathion they were using it to treat coffee trees.
For assistance in assessing the likelihood of resistance, conducting resistance testing, and selection of alternative insecticides and control procedures.