Biology and host specificity ofChamaesphecia hungarica andCh. Astatiformis (Lep.: Sesiidae) two candidates for the biological control of leafy spurge,Euphorbia esula (Euphorbiaceae) in North America

Leafy spurge (Euphorbia esula (s.1.)) is an herbaceous perennial and serious weed of Eurasian origin that has been accidentally introduced into North America. The two European root-boring mothsChamaesphecia hungarica andCh. astatiformis are univoltine and overwinter as mature larvae. Both species have a lower survival rate on leafy spurge than on their field hosts, and thus are not optimal candidates for the biological control of leafy spurge. However, the rate of larval development and larval growth on the target weed and on the two field hosts is nearly the same. The experimental host range of both species is restricted to a few species in the subgenusEsula within the genusEuphorbia. The two species occupy different habitats in the steppe biome and are targeted for similar leafy spurge habitats in North America.