When an insect is killed after crawling over an insecticide residue, this is referred to as what kind of control?

The scenario describes a situation where an insect comes into contact with an insecticide residue and subsequently dies as a result. This situation is characterized as indirect contact control. In this method, the insect does not have to be directly sprayed or actively engaged with the insecticide at the time of application; instead, it can encounter the substance later on, resulting in its death. This approach is particularly useful for targeting pests that might hide or reside in treated areas without being directly in the line of the insecticide application.

The other options represent different approaches to pest control. Direct contact involves applying the insecticide directly onto the pest at the time of application, effectively killing it immediately. Biological control refers to the use of natural predators or parasites to reduce pest populations, while cultural control encompasses practices that modify the environment to prevent pest establishment or reduce their impact. Each of these methods employs distinct mechanisms that differ fundamentally from the residue-based action described in the question.