It has been previously demonstrated that combinations of grassy weeds (Setaria and Digitaria species) with transgenic corn produce more western corn rootworm adults when the weeds are sprayed with herbicide shortly after larval hatch than either the transgenic corn alone or the weeds alone. It is unknown how long dying root tissue supports corn rootworm development. The purpose of this study was to determine how long senescing root tissue supports larval growth. In addition to evaluating senescing Setaria species, maize roots were killed by either chopping the plant below the growing point or with glyphosate to simulate adult emergence studies and volunteer corn respectively. To determine when dying maize and foxtail plants are no longer nutritious, initial weight of the larvae were recorded and weight gain on each treatment recorded for both neonate and second instar western corn rootworm larvae after 5, 10, or 15 days of feeding. The treatments for maize and Setaria were: living control plants, plants cut or sprayed on the day they were infested, plants cut or sprayed 5 and 10 days early and were planted 5 and 10 days early. Each of the three experiments was repeated a minimum of twice with five replications each set up in a randomized block design. In addition to larval recovery there was an adult emergence pot for each treatment and replication. Western corn rootworm larvae survived newly killed plants well, but root tissue killed more than 5 days earlier lacks full nutrition.