cone-shaped galls on leaves, stems, and buds...Rhopalomyia chrysanthemi (Ahlberg)

Severe infestations can cause the plants to become deformed and bear a reduced number of blooms....It arrived in North America probably as early as 1900. Hosts: Chrysanthemum spp., including cultivars. Distr.: cosmopolitan, wherever chrysanthemums are grown, although no longer common in North America