Chrysanthemum Gall Midge

The chrysanthemum gall midge (Rhopalomyia chrysanthemi) is a small fly in the family Cecidomyiidae (gall midges), a specialist pest of cultivated chrysanthemums (Chrysanthemum spp.) and closely related plants in the family Asteraceae. Female midges lay eggs on the leaves and stems of chrysanthemums, and the developing larvae secrete chemicals that stimulate the host plant to form characteristic galls — abnormal swellings or outgrowths of plant tissue that enclose and protect the larvae. The galls caused by Rhopalomyia chrysanthemi are typically green to yellowish, irregular, blister-like swellings on the leaf surface or along the stem, disfiguring the ornamental plant and reducing its commercial value. The pest was originally of East Asian origin and has spread through the international trade in chrysanthemum cuttings to become a pest in Europe, North America, and other chrysanthemum-producing regions. Infested plant material is a primary vector for spread, and phytosanitary regulations in many countries require inspection and treatment of imported chrysanthemum stock. Management relies on sanitation, removal of infected material, and in some cases chemical treatments, though the enclosed nature of the larvae within galls limits the effectiveness of contact insecticides.