Three species of aphids are vectors of potyviruses that infect commercial field production of calla lily in California. Since there is evidence that imidacloprid can have a significant effect on disease transmission by vectors, a field trial using imidacloprid injected through drip tape lines was conducted at a cooperating growers facility. Imidacloprid was applied at the highest recommended label rate – either as a single application or as a split rate in which two applications were made with an interval of two weeks between each treatment. Within leaf concentrations of imidacloprid were assessed over time, and assays of imidacloprid concentration against the green peach aphid were also conducted. We have determined that (1) plant position in the field with respect to the drip tape and (2) distance from the injection point have an effect on the concentration of imidacloprid in the leaves. In addition, two applications of imidacloprid at half the highest recommended rate causes an increase in concentrations over time that exceed the levels observed in calla leaves treated once with the highest recommended rate. Older leaves consistently exhibited a higher concentration than young or new leaves as they flush.