The efficacy of novaluron (Diamond™ 0.83 EC) on cotton, Gossypium hirsutum L., against nymphs of different instars of field-collected southern green stink bug, Nezara viridula (L.), was investigated in a spray chamber using two nozzles, 650033 and 8002E. The nozzles delivered rates of 18.7 and 46.7 L/ha, respectively, of total water-based spray. Novaluron was applied at 0.0218, 0.0436 and 0.0654 kg active ingredient (AI) rates per ha. The 8002E nozzle produced significantly larger droplets, increased droplet density and increased spray coverage compared to the 650033 nozzle. Regardless of dosage and spray rate, the age of nymphal instars significantly influenced mortality. Mortality of small nymphs (2^nd instars) was significantly greater than that of either 3^rd- or 4^th-instar nymphs. When novaluron was applied at 0.0654 and 0.0872 kg AI per ha with or without crop oil concentrate, the deposit from the 8002E nozzle significantly increased mortality of 3^rd-instar nymphs; however, neither dosage nor addition of crop oil concentrate increased mortality of 3^rd-instar nymphs. Novaluron did not cause a great amount of mortality of 4^th-instar nymphs. This study suggests that application of novaluron should be directed at 2^nd-instar nymphs to maximize efficacy for control of southern green stink bug on cotton and that applications that produce deposits with increased droplet size and density on plants might increase efficacy.