At some level of carpenter bee activity, the risk of damage justifies the action. The action threshold might, for example, be set at an average of one carpenter bee per five linear feet. The action threshold for ticks by a school athletic field would be set much lower if Lyme disease was common in the area. Mosquito action thresholds would be lowered if there was an outbreak of encephalitis. The threshold for poisonous black widow spiders would be much lower than for garden spiders.
Aesthetic damage occurs when the appearance of something is degraded.
Examples include bird droppings on sidewalks or spider webs along a walkway. People often disagree on aestheticswhat is acceptable to one person may not be to another. Unfortunately, aesthetic thresholds in structural pest control are not as clear cut as in, say, landscape pest control, where research has shown that control action is considered necessary by most people when a pest has damaged roughly 10 percent of an ornamental shrub or tree. The reasons are complex, based on social, cultural or psychological factors. Most people are less willing to tolerate a cockroach than a cricket, a tick than a beetle, a mouse than a pigeon.