Efficacy and host specificity compared between two populations of the psyllid Aphalara itadori, candidates for biological control of invasive knotweeds in North America

► Two populations of the psyllid Aphalara itadori are effective at reducing knotweed growth and biomass. ► The two populations differ in their performance among different knotweed species. ► Development of A. itadori occurred infrequently on several non-target plant species. ► The psyllid exhibited non-preference and an inability to persist on non-target plants.