In crop production, such as agriculture and horticulture, there is continuing substantial damage by pests and so forth, and the development of novel agricultural/horticultural insecticides is desireddue to factors such as the emergence of pests that are resistant to existing chemicals. The present invention provides an agricultural/horticultural insecticide in which an active ingredient is a 4H-pyrrolopyridine compound represented by general formula (1) [in the formula, R1 represents a halogen atom; R2 and R3 each represent a haloalkyl group; Q represents Q-A, Q-B, or Q-C; X represents a nitrogen atom; R4 and R7 each represent a hydrogen atom; R2 and R3 each represent a halogen atom, haloalkyl group, or substituted phenyl group; and m represents 2] or salt thereof, and also provides a method for using this insecticide.