Cotton at the 2-leaf stage was manually infested with small (1^st-2^nd instar), medium (3^rd instar) and large (5^th instar) tarnished plant bug nymphs in a field study in Northeastern Arkansas. One lab reared nymph was released per plant on 23 May (15 DAP). Plants were monitored weekly through cutout using COTMAN™ with end of season final mapping conducted using COTMAP. At 18 days after treatment the medium and large bug treated plants had significantly fewer leaves and fewer actively growing terminals compared to the untreated check and small bug treatments. A significant reduction in no. of squaring nodes per plant prior to first flowers in the medium and large nymph treatments indicates that injury was more severe than that associated with the small nymphs. There were significant differences in yield during the 1^st and 2^nd harvest; however, no differences were observed during the 3rd and 4^th harvest. Results from mean maturity date calculations indicated a significant delay of 6 days associated with injury from large nymphs.