Some pergids can be economically important because of their defoliation. Species of Tequus feed on potato in Peru and Bolivia, Cerospastus volupis defoliates Nothofagus in Chile and Argentina, a large number of species defoliate (Perginae) or mine in the leaves (Phylacteophaga) of various species of Eucalyptus in Australia. In particular the leafminers of the genus Phylacteophaga have been of concern in New Zealand and New Caledonia since being introduced into those countries.
Species of Haplostegus, Enjijus, and Sutwanus feed on the foliage or are shoot borers of guava, Psidium spp., in Central and South America, and Acordulecera species defoliate oaks and hickories in the eastern North American deciduous forests. Some species are of concern to agriculture in Australia (Queensland), Brazil, and Uruguay where larvae are known to be poisonous to livestock if ingested (e.g. Lophyrotoma interrupta, Perreyia lepida).
Two species are of potential value as biological control agents of invasive weeds in the United States. Lophyrotoma zonalis from Australia has been considered for release against Melaleuca quinquenervia in Florida, and Heteroperreyia hubrichi against the Brazilian Peppertree, Schinus terebinthifolius.