DEVELOPMENTAL PERFORMANCE OF THE WEEVIL EUHRYCHIOPSIS-LECONTEI ON NATIVE AND EXOTIC WATERMILFOIL HOST PLANTS

We investigated the developmental performance of the submersed watermi lfoil specialist Euhrychiopsis lecontei (Dietz) (Curculionidae) on its native host, northern watermilfoil Myriophyllum sibiricum Komarov, an d its newly acquired exotic host, Eurasian watermilfoil Myriophyllum s picatum L. The weevil is a potential biological control agent of Euras ian watermilfoil, To determine if performance is affected by rearing p lant or by maternal plant, we examined development of eggs from Eurasi an and northern watermilfoil-reared mothers on both species of watermi lfoil. 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 deg rees C and 16-19 d at 19.5 degrees C with survival ranging from 50 to 100% for the larval stage and 60 to 88% for the pupal stage. Overall d evelopmental time from egg to adult was 23-26 d at 25 degrees C with s urvival from egg to adult ranging from 20 to 70%. Development times we re significantly longer (1-3 d) on the native northern watermilfoil th an on Eurasian watermilfoil. Survival did not differ significantly amo ng rearing plant, but progeny of Eurasian watermilfoil-reared parents performed more poorly on northern watermilfoil than did progeny of nor thern watermilfoil-reared parents. Adult emergence weight did not vary by rearing plant, but was affected by maternal factors. Thus, there i s no developmental performance penalty for shifting to the exotic host and there is evidence of better performance on the exotic host than o n the native host.