Gypsy moth (Lepidoptera : Lymantriidae) feeding on purple loosestrife (Lythrum salicaria) in Michigan

Purple loosestrife, Lythrum salicaria, is an exotic invasive weed which is currently the target of a biological control effort using introduced leaf-f eeding beetles. In 1997-1998 we observed larvae of the gypsy moth, Lymantri a dispar feeding on L. salicaria at several locations in south central Mich igan. In one-minute timed counts conducted over a six-week period in 1998, densities of 0 to 8 larvae per 1-m(2) quadrat were observed. Other observat ions indicated 23 L. dispar 2nd and 3rd instars on a single L. salicaria pl ant. Second and third instar L. dispar collected on L. salicaria in the fie ld were successfully reared to the adult stage in the lab on a diet oft. sa licaria foliage. This is the first report of L. dispar feeding and developm ent on L. salicaria. In areas where they co-occur, distinguishing L. dispar damage from that of introduced natural enemies will be important so that e stimates of biocontrol agent impact are not biased.