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 desired due 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, R