I P M relies heavily on

Answer: Option A

I P M relies heavily on Economic threshold level.
Integrated pest management (is a way to control insects without relying solely on pesticides. It uses long-term prevention of pests or their damage through a combination of techniques such as biological control, habitat manipulation, change of cultural practices, and uses resistant plant varieties.
Economic Threshold Level (ETL) is the index for making pest management decisions. It is defined as the pest population density at which control measures should be initiated against an increasing pest population to prevent economic damage.