Developmental performance of the weevil Euhrychiopsis lecontei on native and exotic watermilfoil host plants

We investigated the developmental performance of the submersed watermilfoil specialist Euhrychiopsis lecontei (Dietz) (Curculionidae) on its native host, northern watermilfoil Myriophyllum sibiricum Komarov, and its newly acquired exotic host, Eurasian watermilfoil Myriophyllum spicatum L. The weevil is a potential biological control agent of Eurasian watermilfoil. To determine if performance is affected by rearing plant or by maternal plant, we examined development of eggs from Eurasian and northern watermilfoil-reared mothers on both species of watermtifoil. Hatching occurred in 3-5 d, and egg emergence rate ranged from 60 to 100%. Larval and pupal stages were completed in 8-11 d at 25°C and 16-19 d at 19.5°C with survival ranging from 50 to 100% for the larval stage and 60 to 88% for the pupal stage. Overall developmental time from egg to adult was 23-26 d at 25°C with survival from egg to adult ranging from 20 to 70%. Development times were significantly longer (1-3 d) on the native northern watermilfoil than on Eurasian watermilfoil. Survival did not differ significantly among rearing plant, but progeny of Eurasian watermilfoil-reared parents performed more poorly on northern watermilfoil than did progeny of northern watermilfoil-reared parents. Adult emergence weight did not vary by rearing plant, but was affected by maternal factors. Thus, there is no developmental performance penalty for shifting to the exotic host and there is evidence of better performance on the exotic host than on the native host.