Nalepellinae
Guides
Trisetacus
Trisetacus is a genus of eriophyoid mites (Eriophyoidea: Phytoptidae, historically placed in Nalepellidae) that are obligate parasites of coniferous trees. Species within this genus exhibit strong host specificity, primarily infesting members of Pinaceae and Cupressaceae. The genus includes species with diverse feeding habits: some inhabit needle sheaths, others infest foliage, buds, or seeds. Molecular phylogenetic studies have revealed a deep dichotomy within Trisetacus, with two major lineages distinguished by female genital morphology and host associations—one lineage associated with Pinaceae and another with Cupressaceae. Several species are significant forest pests, causing damage ranging from needle chlorosis and twisting to complete destruction of seed crops. The genus has been subject to taxonomic revision, with 22 species recognized from North America alone.