Host range expansion by the invasive herbivore Corythucha marmorata (Uhler, 1878) is not caused by better quality of new hosts.
Phytophagous insects may become serious pests of crops when introduced into a new place. Better nutritional quality and lower toxicity of new host plants and escape from natural enemies can enhance survival. The chrysanthemum lace bug, Corythucha marmorata (Hemiptera: Tingidae), is native to North America, where it exploits mainly goldenrod and its relatives (Asteraceae). It was accidentally introduced into Japan by about 2000. Since then, many reports of injury to sweet potato (Convolvulaceae) and eggplant (Solanaceae) by this species have been published. Here, we tested larval performance on goldenrod, sweet potato, eggplant, and three other known or potential host plants to investigate why the lace bug began to exploit the new host plants. Survival to adult stage was nil on eggplant, extremely low on blue daze (Convolvulaceae) and crown daisy (Asteraceae), moderate on sweet potato, and ca. 80% on goldenrod and sunflower. Developmental time was shorter and adults grew larger on goldenrod and sunflower than on the other plants. These results show that plant nutritional or toxicological qualities are not major factors that facilitate host range expansion of C. marmorata in Japan. Possible factors are discussed.