A difficulty faced by growers using nucleopolyhedrovirus (NPV) products such as Gemstar can be inconsistency of the products' performance for Helicoverpa spp. control. This problem has lead to the advent of additives developed to improve biopesticide performance. In this paper we investigated several liquid additives for their potential to augment the performance of Gemstar. The results suggest that Aminofeed and Aminofeed UV both increase the efficacy of Gemstar.