What is a key indicator of resistance in a pest population?

Continued pest damage despite treatment is a key indicator of resistance in a pest population because it suggests that the pests have developed the ability to survive the pesticide applications that previously would have been effective in controlling them. When a population of pests becomes resistant, they may not respond to the same chemicals that were once successful in managing their numbers, leading to ongoing damage in crops or other treated areas. This resistance can occur through genetic changes in the pest population, selecting for individuals that can tolerate or evade the effects of the pesticide.

The other choices relate to pest management and monitoring but do not directly indicate resistance. A decreased pesticide application rate may be a result of adopting more sustainable practices or integrated pest management strategies rather than a sign of resistance. Increased population growth can occur due to normal reproductive patterns and does not necessarily imply resistance if control measures are still effective. More frequent pest monitoring is a good practice for managing pests but does not in itself indicate the development of resistance; it might just reflect a proactive approach to pest management.