<p>Scale insects are ubiquitous herbivores that are frequently transported on plants through horticultural trade and are encountered at ports of entry worldwide. We provide an update on the non-native species of scale insects that have been introduced to the continental United States including: the species involved, their host associations, pest status, introduction rates, invasion pathways, and we estimate their economic impact on U.S. agriculture. There are 1099 species of scale insects recorded in the continental U.S., 297 are non-native species (27%). Introduced species belong to 16 families, the most common of which are Diaspididae (150), Pseudococcidae (63), and Coccidae (44). These species are often pests; 216 species (73%) are minor to major horticultural pests or are recently introduced and have the potential to become pests. Over half (56%) of introduced scale insects are polyphagous, able to survive and reproduce on many host plant families, and the most impacted commodities include deciduous and tropical fruiting trees (e.g., apple, banana, citrus, grapevine, stone fruits), landscape and ornamental plants (e.g., exotic trees, shrubs, palms, roses), grasses (e.g., ornamentals including bamboos, cereal grain crops, sugarcane), houseplants (e.g., cacti, orchids, snake plants, succulents), trees (e.g., conifers and hardwoods), and miscellaneous other commodities (e.g., cut flowers, cotton, coffee). Scale insects are estimated to cost U.S. agriculture and consumers between $4–8 billion USD annually in production losses and management costs. We discuss the impact of plant quarantine measures and expectations about future species introductions.</p>